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I wonder if there is a really tiny GPS device that can be mounted on passerine birds (or circa 10 grams birds) without affecting their flight. This web site shows information for bat's GPS. But it also only last for 24 hours. I wonder if there is some lightweight and long battery life about 2-5 grams. I found this also, but haven't found if it contains a long battery life.
Is there a study on GPS tracking small birds?
The technology is not there (yet) for deployments on 10 gram birds. The limits for GPS technology are around the 50 g range, for birds. Also bear in mind that the smallest loggers are generally not capable of transmitting, so you would need to recapture the animals to retrieve your data.
As your question implies, there is a strong trade-off between device weight and battery life. There are GPS devices weighing as little as 1 g, but their lifespan is very limited (10 fixes for the 1 g device; 50 for a 1.1 g device).
As a side note: your question implies that small passerines can carry 20 - 50 % of their body mass in tracker without their flight being affected. The ethics boards I am familiar with generally limit trackers to ~ 5 % of the mass of the animal.
Parental provisioning behaviour in a flock-living passerine, the Vinous-throated Parrotbill Paradoxornis webbianus
The amount of food delivered by parents to their chicks is affected by various life history traits as well as environmental and social factors, and this investment ultimately determines the current and future fitness of parents and their offspring. We studied parental provisioning behaviour in the Vinous-throated Parrotbill Paradoxornis webbianus, a species with an unusual social system that is characterised by flock-living, weak territoriality and variable nesting dispersion. Parental provisioning rate had a positive influence on chick mass gain, suggesting that provisioning rate is an effective measure of parental investment in this species. Males and females fed nestlings at approximately the same rate, and no other carers were observed at nests. Parents coordinated provisioning rates so that they mostly fed chicks synchronously. However, the extent to which parents coordinated provisioning was associated with their social environment, synchrony being positively related to local breeding density and negatively to nearest neighbour distance. The rate at which parents provisioned nestlings showed the same relationships with social measures, being greatest at higher density and when neighbours were closer. Visit rate was also related to chick age, but not to brood size, brood sex ratio, extra pair paternity, laying date, temperature, parents’ body characters, time of day or year. We conclude that a breeding pairs’ social environment plays an important role in determining parental investment, probably through its effects on the opportunities that parents have for foraging with conspecifics.
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Five Practical Uses for “Spooky” Quantum Mechanics
Quantum mechanics is weird. The theory, which describes the workings of tiny particles and forces, notoriously made Albert Einstein so uneasy that in 1935 he and his colleagues claimed that it must be incomplete—it was too “spooky” to be real.
The trouble is that quantum physics seems to defy the common-sense notions of causality, locality and realism. For example, you know that the moon exists even when you’re not looking at it—that's realism. Causality tells us that if you flick a light switch, the bulb will illuminate. And thanks to a hard limit on the speed of light, if you flick a switch now, the related effect could not occur instantly a million light-years away according to locality. However, these principles break down in the quantum realm. Perhaps the most famous example is quantum entanglement, which says that particles on opposite sides of the universe can be intrinsically linked so that they share information instantly—an idea that made Einstein scoff.
But in 1964, physicist John Stewart Bell proved that quantum physics was in fact a complete and workable theory. His results, now called Bell’s Theorem, effectively proved that quantum properties like entanglement are as real as the moon, and today the bizarre behaviors of quantum systems are being harnessed for use in a variety of real-world applications. Here are five of the most intriguing:
A strontium clock, unveiled by NIST and JILA in January, will keep accurate time for the next 5 billion years. (The Ye group and Brad Baxley, JILA)
Reliable timekeeping is about more than just your morning alarm. Clocks synchronize our technological world, keeping things like stock markets and GPS systems in line. Standard clocks use the regular oscillations of physical objects like pendulums or quartz crystals to produce their ‘ticks’ and ‘tocks’. Today, the most precise clocks in the world, atomic clocks, are able to use principles of quantum theory to measure time. They monitor the specific radiation frequency needed to make electrons jump between energy levels. The quantum-logic clock at the U.S. National Institute of Standards and Technology (NIST) in Colorado only loses or gains a second every 3.7 billion years. And the NIST strontium clock, unveiled earlier this year, will be that accurate for 5 billion years—longer than the current age of the Earth. Such super-sensitive atomic clocks help with GPS navigation, telecommunications and surveying.
The precision of atomic clocks relies partially on the number of atoms used. Kept in a vacuum chamber, each atom independently measures time and keeps an eye on the random local differences between itself and its neighbors. If scientists cram 100 times more atoms into an atomic clock, it becomes 10 times more precise—but there is a limit on how many atoms you can squeeze in. Researchers’ next big goal is to successfully use entanglement to enhance precision. Entangled atoms would not be preoccupied with local differences and would instead solely measure the passage of time, effectively bringing them together as a single pendulum. That means adding 100 times more atoms into an entangled clock would make it 100 times more precise. Entangled clocks could even be linked to form a worldwide network that would measure time independent of location.
Observers will have a tough time hacking into quantum correspondence. (VOLKER STEGER/Science Photo Library/Corbis)
Traditional cryptography works using keys: A sender uses one key to encode information, and a recipient uses another to decode the message. However, it’s difficult to remove the risk of an eavesdropper, and keys can be compromised. This can be fixed using potentially unbreakable quantum key distribution (QKD). In QKD, information about the key is sent via photons that have been randomly polarized. This restricts the photon so that it vibrates in only one plane—for example, up and down, or left to right. The recipient can use polarized filters to decipher the key and then use a chosen algorithm to securely encrypt a message. The secret data still gets sent over normal communication channels, but no one can decode the message unless they have the exact quantum key. That's tricky, because quantum rules dictate that "reading" the polarized photons will always change their states, and any attempt at eavesdropping will alert the communicators to a security breach.
Today companies such as BBN Technologies, Toshiba and ID Quantique use QKD to design ultra-secure networks. In 2007 Switzerland tried out an ID Quantique product to provide a tamper-proof voting system during an election. And the first bank transfer using entangled QKD went ahead in Austria in 2004. This system promises to be highly secure, because if the photons are entangled, any changes to their quantum states made by interlopers would be immediately apparent to anyone monitoring the key-bearing particles. But this system doesn't yet work over large distances. So far, entangled photons have been transmitted over a maximum distance of about 88 miles.
Closeup of a D-Wave One computer chip. (D-Wave Systems, Inc.)
A standard computer encodes information as a string of binary digits, or bits. Quantum computers supercharge processing power because they use quantum bits, or qubits, which exist in a superposition of states—until they are measured, qubits can be both "1" and "0" at the same time.
This field is still in development, but there have been steps in the right direction. In 2011, D-Wave Systems revealed the D-Wave One, a 128-qubit processor, followed a year later by the 512-qubit D-Wave Two. The company says these are the world's first commercially available quantum computers. However, this claim has been met with skepticism, in part because it’s still unclear whether D-Wave’s qubits are entangled. Studies released in May found evidence of entanglement but only in a small subset of the computer’s qubits. There's also uncertainty over whether the chips display any reliable quantum speedup. Still, NASA and Google have teamed up to form the Quantum Artificial Intelligence Lab based on a D-Wave Two. And scientists at the University of Bristol last year hooked up one of their traditional quantum chips to the Internet so anyone with a web browser can learn quantum coding.
Keeping a sharp eye on entanglement. (Ono et al., arxiv.org)
In February a team of researchers at Japan’s Hokkaido University developed the world’s first entanglement-enhanced microscope, using a technique known as differential interference contrast microscopy. This type of microscope fires two beams of photons at a substance and measures the interference pattern created by the reflected beams—the pattern changes depending on whether they hit a flat or uneven surface. Using entangled photons greatly increases the amount of information the microscope can gather, as measuring one entangled photon gives information about its partner.
The Hokkaido team managed to image an engraved "Q" that stood just 17 nanometers above the background with unprecedented sharpness. Similar techniques could be used to improve the resolution of astronomy tools called interferometers, which superimpose different waves of light to better analyze their properties. Interferometers are used in the hunt for extrasolar planets, to probe nearby stars and to search for ripples in spacetime called gravitational waves.
The European robin may be a quantum natural. (Andrew Parkinson/Corbis)
Humans aren't the only ones making use of quantum mechanics. One leading theory suggests that birds like the European robin use the spooky action to keep on track when they migrate. The method involves a light-sensitive protein called cryptochrome, which may contain entangled electrons. As photons enter the eye, they hit the cryptochrome molecules and can deliver enough energy to break them apart, forming two reactive molecules, or radicals, with unpaired but still entangled electrons. The magnetic field surrounding the bird influences how long these cryptochrome radicals last. Cells in the bird’s retina are thought to be very sensitive to the presence of the entangled radicals, allowing the animals to effectively ‘see’ a magnetic map based on the molecules.
This process isn't full understood, though, and there is another option: Birds' magnetic sensitivity could be due to small crystals of magnetic minerals in their beaks. Still, if entanglement really is at play, experiments suggest that the delicate state must last much longer in a bird’s eye than in even the best artificial systems. The magnetic compass could also be applicable to certain lizards, crustaceans, insects and even some mammals. For instance, a form of cryptochrome used for magnetic navigation in flies has also been found in the human eye, although it’s unclear if it is or once was useful for a similar purpose.
A brief history
About 40 years ago a simple experiment conducted in Tuscany changed the course of research on bird navigation: a group of pigeons with their olfactory nerves sectioned were released at an unfamiliar site and never returned their intact companions rapidly flew back to the loft (Papi et al., 1971). At that time the olfactory sense was considered marginal in birds and olfactory cues had never been seriously taken into account among the possible sources of environmental information potentially useful for a position-finding mechanism. For this reason it might seem quite odd that a test release with anosmic pigeons was even conceived. Floriano Papi thought of testing the navigational abilities of anosmic homing pigeons because this sense was the only one (along with taste) not yet tested as potentially important in navigation. However, an important piece of information eventually prompted the first homing experiment with anosmic birds. At about the same time, Wallraff and colleagues were investigating the behaviour of pigeons raised in confined aviaries and exposed to different environmental stimuli. Their research aimed at testing whether a view of the horizon was critical for the pigeons to develop unimpaired navigational ability. Testing birds raised confined in an aviary provided with glass screens and birds raised in an aviary surrounded by a palisade, which prevented the full view of the horizon, they expected to observe an impairment only in the latter group. The results were clearly against expectations: the pigeons allowed to view the horizon, but sheltered from the winds by glass screens, were unable to orient towards home. By contrast, birds exposed to the winds passing through the palisade were unimpaired, even if the view of the surroundings was obstructed. These first results, later confirmed by subsequent experiments, led to the hypothesis that an ‘atmospheric factor’ was likely to be involved in navigation (Wallraff, 1970). In light of these results, testing the navigational abilities of anosmic pigeons did not appear odd. Both the results of Wallraff and Papi are explained by the ‘olfactory navigation hypothesis’ proposed by Papi (Papi et al., 1972): pigeons at their home area are able to learn windborne environmental odours in association with wind direction once at the release site they are able to recognise the prevalent local odours and recall from which direction these odours come from at the home area in order to determine the direction of displacement (Fig. 1).
The evidence that local release site odours constitute a source of navigational information for homing pigeons has been demonstrated in an elegant experiment by Benvenuti and Wallraff (Benvenuti and Wallraff, 1985), in which the birds were fooled concerning the release site olfactory information. Pigeons were transported in airtight containers ventilated by air purified by charcoal filters to a false release site where they were allowed to breath local environmental air for a few hours. Then the birds were transported in pure air to a new site located in the opposite direction with respect to home, subjected to nasal anaesthesia and released. At the false release site these birds had experienced the local odours, while at the true release site this kind of information was not accessible. The birds oriented towards the ‘false home direction’, i.e. the home direction from the false release site, while the control birds exposed to the local air at the true release site oriented towards home.
Our study used both field and laboratory data to examine how a small, insectivorous, sedentary, group-living passerine, a likely candidate for avian torpor, survives in an energetically challenging environment. Overnight measurement of Tb indicated that free-living white-browed babblers maintained normothermia over a wide range of Ta and did not use torpor or hibernation. Complementary laboratory experiments of individual and group-huddling physiology showed that roosting babblers derived energetic benefits from social thermoregulation, as well as the use of insulated roost nests. Our findings suggest that heterothermia may indeed be uncommon amongst Austral passerines, and that birds with a mostly typical avian physiology can offset the considerable energetic costs of endothermy with behavioural strategies to minimise heat loss and maintain a year-round existence in a variable environment.
Free-ranging babblers maintained a near-constant Tb overnight, despite low, frequently sub-zero, overnight Tbb. The range of Tb,field for all individuals was <2.2°C under all environmental conditions, and varied more between individuals than as a response to environmental conditions. Although torpor and hibernation have been observed only infrequently in a small number of avian families (Geiser et al., 2006), the capacity for nocturnal hypothermia is generally considered to be widespread (McKechnie and Lovegrove, 2002). However, there was no evidence here that hypothermia was an important part of the babblers' energetic strategy, other than their typical homeothermic scotophase pattern (Schmidt-Nielsen, 1997 Fig. 1). Babblers warmed endogenously for roost departure at sunrise to a similar Tb to that at roost arrival. Both mean active-phase Tb (Tb,depart 40.4°C) and rest-phase Tb (minimum Tb,field 38.5°C) were similar to those for other normothermic passerines (41.6±1.13 and 38.9±0.87°C, respectively Prinzinger et al., 1991). In the laboratory, individual babblers at Ta=10°C maintained Tb only 1.0°C lower than at thermoneutrality (38.6°C at Ta=30°C), achieved by a 143% increase in MR (accommodated by increased ventilatory VI) and a 15.7% decrease in Cwet a typical endothermic response.
Globally, non-passerines and particularly nocturnal species are more likely to be heterothermic, and much thermoregulatory research has focused on these species (e.g. Brigham, 1992 Körtner et al., 2001 Lane et al., 2004 McKechnie et al., 2007 Cooper et al., 2008 Smit and McKechnie, 2010 Doucette et al., 2011, 2012). However, only a handful of studies have documented the nocturnal energetic strategy of free-ranging passerines, and even fewer have measured core Tb. White-throated sparrows (Zonotrichia albicollis) have a rest-phase hypothermia, with a 3.4°C reduction in Tskin between active and rest phase (Dolby et al., 2004) and the diel variation in Tb of the arid-dwelling white-browed sparrow-weaver (Plocepasser mahali) is attributed to seasonal environmental conditions (Smit et al., 2013). The only comparable measurement of continuous, nocturnal Tb of an Australian passerine in the cold is for captive-raised juvenile dusky woodswallows (Artamus cyaneurus Maddocks and Geiser, 2007), measured in outdoor aviaries. These birds used heterothermy overnight Tb,min decreased by >5°C from resting Tb, which the authors classified as daily torpor. These data, based on skin temperature or for captive birds, suggest that heterothermia amongst passerines may be more common than currently recognised. As sedentary, insectivorous birds in a semi-arid habitat, white-browed babblers have characteristics that suggest they are likely candidates for torpor use, and indeed have other adaptations such as sociality and cooperative breeding associated with harsh and unpredictable environmental conditions they therefore may be considered a good model for avian heterothermia. However, their lack of torpor, or indeed any significant heterothermy, suggests that avian torpor use may be rare, particularly compared with small mammals, if their general physiology is similar to other passerines, and indeed other birds. In this case, the paucity of data quantifying avian heterothermy may not just represent a lack of research in this area as is currently assumed (Astheimer and Buttemer, 2002 McKechnie and Lovegrove, 2002 Geiser et al., 2006).
Babblers had a typical endothermic response to Ta above and below thermoneutrality in the laboratory. A near-constant Tb was maintained by an increase in metabolic heat production at low Ta. This increase in O2 demand was accommodated by an increase in fR and VT rather than EO2, which is typical of both birds and mammals (e.g. Larcombe et al., 2003 Cooper and Withers, 2004). Thermal conductance remained close to minimal below thermoneutrality, but increased at higher Ta, as did EWL, as babblers increased their heat dissipation. The PRWE of 17.5°C was particularly high and presumably contributes to maintenance of water balance in the absence of free water, and is at least partly facilitated by homeothermy at low Ta.
To best interpret the physiological basis for our observations of nocturnal homeothermy for free-living babblers, it is necessary to examine their standard physiology in an allometric and phylogenetic context. For mammals, low Tb and low BMR correlate with the use of heterothermy and torpor (Geiser, 1998 Cooper and Geiser, 2008 Ruf and Geiser, 2014) and we assume a similarity in physiological drivers between convergently endothermic mammals and birds. We therefore compared here our standard physiological data for babblers with those of other birds (Table S6) using the 95% prediction limits (Cooper and Withers, 2006) for conventional and phylogenetically informed allometric regressions after Barker et al. (2016), using the phylogenetic tree from birdtree.org (Jetz et al., 2012, 2014) with the Hackett backbone (Hackett et al., 2008).
Standard Tb of babblers statistically conformed to that of other birds, both before and after correcting for phylogeny, as did their Cwet, suggesting there is nothing remarkable about babbler's insulation or heat balance (Fig. 7). Our value of BMR for solitary-roosting white-browed babblers (Mb 46 g) of 1.24 ml O2 g −1 h −1 was similar to, but lower than, the 1.51 ml O2 g −1 h −1 measured by Chappell et al. (2016) for the chestnut-crowned babbler (Pomatostomus ruficeps Mb 50 g), despite our birds having a less arid habitat and slightly lower Mb, suggesting no stress response for solitary-roosting white-browed babblers. White-browed babblers had a BMR that was only 64.0% of that predicted by Mb. Although it was within the 95% prediction interval for the conventional allometric analysis, it was below the prediction limits after accounting for phylogeny (Fig. 7), indicating that babblers have a lower BMR than their nearest relatives. Low BMR is correlated with a propensity for torpor (Cooper and Geiser, 2008), presumably reflecting similar adaptation to a low-energy strategy. Despite this, we found no evidence of torpor for free-living babblers, suggesting their low BMR, together with strategies such as social thermoregulation and insulated roost nests, is sufficient to balance their energy budget.
Allometric and phylogenetic comparisons of physiological variables for white-browed babblers with those of other birds. Tb (A), basal metabolic rate (BMR B), Cwet (C) and EWL (D) for white-browed babblers (black symbols) compared with other birds (grey symbols see Table S6). Mb, body mass. Phylogenetically independent residuals for the same parameters are shown in E–H. Solid lines indicate the least squares regression and dotted lines the 95% prediction intervals for each allometric relationship.
Allometric and phylogenetic comparisons of physiological variables for white-browed babblers with those of other birds. Tb (A), basal metabolic rate (BMR B), Cwet (C) and EWL (D) for white-browed babblers (black symbols) compared with other birds (grey symbols see Table S6). Mb, body mass. Phylogenetically independent residuals for the same parameters are shown in E–H. Solid lines indicate the least squares regression and dotted lines the 95% prediction intervals for each allometric relationship.
Standard EWL was only 41.0% of the allometrically predicted value, and statistically lower than that for other birds, before and after accounting for phylogeny (Fig. 7). Low EWL (like low BMR) is associated with arid habitats (Williams and Tieleman, 2005) and contributes to their high PRWE. This, together with the preformed water of their insectivorous diet, may account for their apparent ability to maintain water balance without drinking, at least in winter (T.K.D., personal observation).
Many social endotherms roost communally (Gilbert et al., 2010), and huddling can play an important role in the maintenance of homeothermy. In extreme cases, communally roosting endotherms are obligate social thermoregulators, unable to regulate normal Tb at low Ta in the absence of conspecifics (e.g. McKechnie and Lovegrove, 2001). White-browed babblers always roosted communally in the field during the study, but even when held individually in the laboratory at Ta as low at 10°C, all babblers maintained Tb within 1.15°C of thermoneutral values. Therefore, babblers are facultative social thermoregulators and although they can survive roosting individually overnight in the wild (Chappell et al., 2016), they gain substantial energetic benefits by huddling.
The reduction in energy expenditure of huddling babblers, with a huddling MR 65–74% of individual MR at an equivalent Ta, is as expected for other huddling endotherms (see Gilbert et al., 2010, for review) and similar to that measured for two to three huddling chestnut-crowned babblers, and is likely to be even greater for more huddling individuals (Chappell et al., 2016). Presumably, the substantial reduction in MR of huddling babblers has a significant role in balancing their energy budget and partially negates the need for heterothermia. However, substantial variation in minimum Tb,field between individuals (∼2.1°C) was observed for free-living babblers (Fig. 2). Location within the roost nest probably impacts overnight Tb there may be a physiological cost associated with social status if social status determines position in a huddle. Thus, individual variation in Tb,field may indicate social status, as observed for vervet monkeys (Chlorocebus pygerythrus McFarland et al., 2015).
Roost nest characteristics
The energetic benefit of roosting in enclosed nests is a further aspect of babblers' nocturnal energy strategy. The Troost of unoccupied babbler nests was the same as Tbb, unlike the nests of sociable weavers (Philetairus socius), which are sufficiently large and well-insulated to remain above ambient conditions overnight even when unoccupied (White et al., 1975). When occupied, the relationship of Troost to Tbb for babbler nests is similar to that of solitary-roosting white-browed sparrow-weavers (P. mahali Ferguson et al., 2002), with the Troost−Tbb differential increasing as Tbb decreases. The thermal conductance of roost nests (C=1.62 J g −1 h −1 °C −1 ) was equivalent to the conductance of groups of two to three huddling babblers (C=1.61 J g −1 h −1 °C −1 at 10°C), so roost nests effectively halve the rate of energy lost to the environment for small groups of huddling babblers. The insulative properties of sparrow-weaver roost nests are an important factor in allowing them to maintain homeothermy at low Ta (Ferguson et al., 2002) and presumably provide similar energetic advantages for white-browed babblers.
For some species, particularly nocturnal birds and bats, roost sites with favourable slope, aspect and entrance direction are selected to allow passive rewarming or to facilitate basking (e.g. Geiser et al., 2004 Turbill and Geiser, 2008). This was not a strategy used by babblers, as there was no preference in roost nest entrance direction, and babblers warmed endogenously prior to sunrise. While babbler roost nests are built preferentially in the top third of their host tree, the variation in host tree species and actual height of the host trees make it unlikely that microclimate considerations are important. A preference for building nests in dense stands of trees may have an energetic benefit, as dense foliage can deflect wind and mitigate radiative heat loss (Walsberg, 1986), but nest location might also be an anti-predator strategy.
The combined use of social thermoregulation and communal roost nests allows substantive energy conservation for white-browed babblers. Minimum overnight babbler Troost was calculated to range from 6.8 to 15.4°C, so the range of MRs for birds in these nests was calculated to be 1.78–2.44 ml O2 g −1 h −1 . Extrapolating the linear relationship between Ta and V̇O2 below thermoneutrality for solitary birds outside roost nests to these Ta, huddling babblers in roost nests would have an energy expenditure only 55–65% of that of single, exposed birds under the same environmental conditions, and this would be even lower for larger groups (e.g. Chappell et al., 2016). In other words, small groups of communal roost-nesting babblers at a Ta of −3 to +15°C and a Troost of 6.8 to 15.4°C would have a MR equivalent to that of a single, exposed bird at a Ta of 17.6 to 24.3°C. These substantial energy savings, together with the birds’ intrinsically low BMR, would play an important role in babblers balancing their daily energy budget, and presumably negate any requirement for torpor in their energetically challenging environment. Therefore, despite a generally typical avian thermal physiology, the energetics and behaviour of the white-browed babbler allow maintenance of homeothermy, and suggest that heterothermy is not a preferred energetic tactic for avian species that can avoid it.
The Inner Lives of Birds
Tweet tweet! We're talking birds, and the incredible things they can do. Today we’re spotlighting five of the coolest recent stories in bird genetics: hummingbirds powering their lightning-fast flight a gene that controls migration why males have different colours to females how light pollution makes sparrows sicker and the bird trapped for thousands of years under the Siberian ice.
In this episode
00:31 - How hummingbirds power their rapid flight
How hummingbirds power their rapid flight Ariel Gershman, Johns Hopkins School of Medicine
The hummingbird is the smallest in the world. They can actually hover mid-air, and uniquely among birds, can fly backwards and upside-down. The quickest of them beats its wings more than eighty times per second. All this aerial acrobatics requires some unique tricks of energy and metabolism - and Phil Sansom heard from Ariel Gershman at the Johns Hopkins School of Medicine, who has been trying to figure out what in their genes makes all this possible…
Ariel - We're really interested in something that hummingbirds do called metabolic flux. They are able to maintain this extremely high metabolism, and extremely high blood sugar, that for most humans would be considered as diabetes but hummingbirds are able to do this without getting any of the ailments associated with diabetes, like blindness, and kidney disease, and all of these other problems that humans who maintain this persistently high blood sugar often experience.
Phil - What's the flux part of that? Is it flux like changing really quickly?
Ariel - The flux is just this rapid shift that they're able to do. So when hummingbirds are eating, they're eating sugar from nectar, and they're able to use the sugar almost entirely to fuel their metabolism, or how they break down that sugar to make energy. But then once they stop feeding, they have to rapidly switch their metabolism to be able to use this fat that they store in their body to then be able to get energy, and power this extremely expensive hovering flight that they're able to do. And so if they weren't able to switch this metabolism so quickly, from their fed state to their fasted state, then they wouldn't be able to continue flying.
Phil - Oh my God, it almost sounds like one of those animals that hibernates in winter and then does all their eating in the summer, but over the course of what, minutes?
Ariel - Yeah. Over the course of 30 minutes is how quickly they're able to switch this fed to fasted metabolism.
Phil - What exactly are you doing to look into this metabolic flux, as you called it?
Ariel - We first had to actually sequence and put together their entire genome. And once we had the whole genome together, we then had to figure out where genes in the genome are. Because only about 1% of the genome actually codes for genes that end up making proteins. And then what we did was we sequenced all of the hummingbird RNA. If you can imagine. the genome is kind of like the blueprint for how to build the organism, whereas the RNA is more like what's actually being made to allow the organism to survive and persist.
Phil - How are you doing this here then, with both the DNA and the RNA?
Ariel - What we mainly focus on is called long read sequencing. Some people call it third generation sequencing. The typical, or the gold standard of DNA sequencing, is this second generation sequencing right now. And in second generation sequencing, it's extremely accurate, but we're only getting small pieces of DNA at a time. Where in third generation sequencing, we're actually sequencing these really, really long molecules of DNA. And if you can imagine, when you're putting together a puzzle, it's a lot easier to put together a puzzle with less pieces that are bigger than a puzzle with more pieces that are smaller. However we lose a little bit of the accuracy with long read sequencing, so it's more likely that there will be mistakes.
Phil - Do you do anything to compensate for that?
Ariel - Yeah, we do. Once we have the entire structure from the long read data we go in and we correct it with the accurate short read data. This is a process that in the field we call hybrid genome assembly.
Phil - Wow. And just for context, how big is the job? How many genes does a hummingbird have?
Ariel - Oh, a hummingbird has around 20 to 30,000 genes. Not that much different than a human actually.
Phil - That's, yeah, quite a few genes to get through.
Ariel - Yeah. And it's actually not even the region of the genome that codes for genes that's the hard part it's really the rest of the genome, that we don't really know a lot about what it does, that's actually the hard part for genome assembly, because a lot of the genome is made up of repetitive DNA. And if you can imagine, if you have the same puzzle piece that fits in multiple locations, you really don't know where it actually goes.
Phil - And what do you do in that situation?
Ariel - The longer reads actually really help us out a lot there. Because when we have the repeat, if we can get the information on either side of it we can anchor it to the right region of the genome.
Phil - These hummingbirds, then, you're giving them a nice big meal, then taking a bunch of blood to get all their DNA and RNA, or what?
Ariel - We're actually taking their liver and their muscle tissue. So those are the really important metabolic tissues.
Phil - With all this incredible third generation sequencing, what are you finding in there?
Ariel - Wow. I wish I had like the cure to diabetes or something crazy. but we're finding a lot of differences in expression in thyroid hormone, which is along the lines of what we expected. What we're really looking for and hoping to find is these glucose transporters. Not a lot is really known about how glucose, sugar, actually gets into the hummingbird cells and how it happens so quickly. Hummingbirds don't seem to have a lot of these genes that humans have that allow sugar to enter our cells. So how was it entering in hummingbirds? We don't know yet. And we're really hoping to figure that out.
Phil - Do you have any personal favourite theories at the moment?
Ariel - I think that this glucose transporter that we're looking for that we don't think is present in hummingbirds. I think that it might be there, it's just that it's in a region of the genome that's so repetitive that previous people who have studied it, haven't been able to find it because of this repeat problem.
The experience-dependent reaction to displacement lends support to Perdeck's paradigm of migratory bird orientation (10). A navigation system presumed to be based on experience has also been shown in caged adult migrants (27, 28). However, previous experiments that tested migratory orientation in cages suggested that juveniles are able to compensate for the displacement. Because adult birds are able to compensate, juvenile birds are supposedly in the process of constructing a navigational map along the migratory route (18). The difference between our study and previous ones could be due to the use of orientation cages, where birds remain within a cage while attempting to depart for migration (22), or alternatively, it may be that our juvenile birds were displaced outside the maximum range of their map that is under construction.
Our study is the first to document age-specific reorientation movements after a continent-wide displacement and within the first hours upon release. It seems highly unlikely that the adult birds used path integration during the displacement to reorient. A path integration system becomes very imprecise over the long distances our birds were displaced.
The results provide insights into the nature of navigation during long-distance migration. On the basis of one migratory journey from Alaska to southwest North America, white-crowned sparrows obtain information that allows them to reach their wintering ground from an area that their normal migratory route does not encompass. Gaining and retaining such information is presumably adaptive because it would allow them to reach their wintering grounds after natural displacements. Juveniles, on the other hand, continue in the species-specific migratory direction after displacement. This suggests that, during migration, homing to a known location is triggered only by reaching that final destination and, possibly, after spending time in it. Because the juvenile birds were caught en route, neither stopovers nor partial travel on the southerly migratory route in the first year seems to trigger homing back to the migratory route. Furthermore, our experiment indicates that the navigational map of adult white-crowned sparrows encompasses at least the continental U.S. and allows them to correct for vast displacements very rapidly (within days, at least), hinting that migratory birds may possess a global navigational map. Even though adult white-crowned sparrows return to a specific winter home range, at this large scale the “map” may just provide a bird with a sign on a gradient, e.g., letting the bird know whether it is east or west of its goal, as observed previously by Åkesson et al. (17).
Currently, magnetic cues seem the most likely candidates for the basis of a map stretching this far (29). However, the small difference in geomagnetic intensity across longitudes in North America makes magnetic intensity an unlikely candidate for distinguishing between the east and the west coast, and celestial or olfactory cues cannot be ruled out (30).
In the past, studies of navigation in passerine birds have generally been restricted to the laboratory because of limitations on field-based study (30). We have demonstrated that it is possible to study the navigation behavior of small migratory birds in the field and provide insights into their behavior. These results demonstrate that the ability to track small animals continuously is essential to gain an understanding of the behavior of free-living migrants. Ultimately, a complete understanding of the mechanisms used by adults and juvenile passerine birds will require a global tracking system for small animals (23).
Study extent description: This dataset covers four representative habitats within the Sierra Nevada mountain range: Pyrenean oak forest, thorny thickets on the edge of the forest, common juniper and Spanish juniper scrublands, and high-summit ecosystems. These ecosystems were selected based on criteria of singularity and ecological functionality in the context of Sierra Nevada (Barea-Azcón et al. 2012, 2014) and can be described as follows:
Pyrenean oak forest: Mediterranean woodland composed mainly of relict Quercus pyrenaica and some dominant scrubland species (i.e. Berberis hispanica, Prunus ramburii, Rosa canina, Crataegus monogyna and Adenocarpus decorticans). These forests show strong evidence of past management that has determined their current structure and diversity. This management is based on mainly charcoal production, pastureland creation, and wood harvesting until the 1950s, so that the current trees are mostly resprouts of individuals 60 to 70 years old. The target localities (n=4) are located at an average elevation of 1650 m a.s.l. (1600-1750 m a.s.l.) and are distributed in the southern, western, northern, and eastern slopes of Sierra Nevada, reflecting all the ecological conditions of the Pyrenean oak forests in the study area (Pérez-Luque et al. 2013).
Thorny scrubs: Typical areas dominated by thorny thickets on the edge of the forest or as result of recent colonization of abandoned arable lands. Berberis hispanica, Prunus ramburii, Rosa canina, Crataegus monogyna are dominant but accompanied by other species such as Lonicera arborea or even Sorbus spp. This open habitat is very important for breeding birds in the study area and also for winter-visiting species due to a great production of fruits from the end of the summer to the beginning of winter. Transects (n=4) in this habitat are located between 1450 and 2060 m a.s.l. (average: 1790 m a.s.l.).
Common juniper and Spanish juniper scrublands: vegetation in these localities is composed mainly of common juniper (Juniperus communis), Spanish juniper (Juniperus sabina). Cytisus galianoi and Genista baetica are also important species in these ecosystems. These scrublands rarely exceed 60 cm in height and appear intermingled with rocks and stony ground. Transects (n=4) located in this ecosystems cover an elevational range from 2000 to 2300 m a.s.l. (average: 2150 m a.s.l.).
High-summit ecosystems: composed by typical Alpine landscape. These ecosystems are characterized by rocky outcrops that originated from glacial activity, pastureland, small snow beds, and glacial lagoons. The four transects representing this Mediterranean high-mountain habitat span an elevational gradient from 2280 to 3100 m a.s.l., with an average elevation of 2580 m a.s.l.
Sampling description: The sampling procedure was the line-transect method (Verner 1985), with a bandwidth of 100 m, with 50 m on each side of the line (Barea-Azcón et al. 2014). Each 50 m band was divided into five ranges parallel to the line transect (comprising a 10 m width each one). A total of 16 transects were sampled with lengths of 1.9 to 3 km (Table (Table2). 2 ). Sight and sound records within the sample area were considered contacts. All transects were sampled in the early morning, under appropriate climatic conditions. The observer walked at a constant speed of 2 to 4 km/h. Transects are repeated at least once per month, snow cover permitting. This implies that the sites located at the higher elevations were sampled only from late spring to early autumn.
Information about transects sampled to collect data included in this dataset.
|Transect name||Length (m)||Habitat type||Longitude||Latitude||Province||Municipality||Elevation (m asl)|
|Robledal de Cá༚r||2556||Pyrenean oak Forest||-3.4292||36.9532||Granada||Cá༚r||1736|
|Robledal de Dílar||2553||-3.4779||37.0582||Granada||Dílar||1605|
|Cortijo del Hornillo||3044||-3.3680||37.1246||Granada||G࿎jar Sierra||1585|
|Dehesa del Camarate||2805||-3.2537||37.1797||Granada||Lugros||1575|
|Dehesa del Río Dúrcal||3292||Thorny thickets||-3.4825||37.0255||Granada||Dúrcal||2033|
|Collado de Matas Verdes||2237||-3.4470||37.0909||Granada||Monachil||1918|
|Collado del Sabinar||2745||Juniper scrublands||-3.4184||37.1199||Granada||G࿎jar Sierra||2036|
|Campos de Otero||2264||-3.3930||37.1100||Granada||G࿎jar Sierra||2143|
|Loma Papeles||2539||-3.3401||37.1434||Granada||G࿎jar Sierra||2113|
|Dehesa de las Hoyas||2436||-3.3173||37.1724||Granada||G࿎jar Sierra||2074|
|Laguna Seca||2530||High-summit ecosystems||-2.9615||37.0992||Granada||Huéneja||2295|
|Hoya Mora||2046||-3.3771||37.0896||Granada||G࿎jar Sierra||2407|
|Papeles alto||2309||-3.3098||37.1357||Granada||G࿎jar Sierra||2420|
Method step description: All data were stored in a normalized database (PostgreSQL) and incorporated into the Information System of Sierra Nevada Global-Change Observatory. Taxonomic and spatial validations were made on this database (see Quality-control description). A custom-made SQL view of the database was performed to gather occurrence data and other variables associated with occurrence data, specifically:
Bird Count: number of individuals recorded by the observer within transect (see Sampling description)
Distance: distance of the contact (bird) from transect line. The distance was estimated by eye.
The occurrence and measurement data were accommodated to fulfil the Darwin Core Standard (Wieczorek et al. 2009, 2012). We used Darwin Core Archive Validator tool (http://tools.gbif.org/dwca-validator/) to check whether the dataset met Darwin Core specifications. The Integrated Publishing Toolkit (IPT v2.0.5) (Robertson et al. 2014) of the Spanish node of the Global Biodiversity Information Facility (GBIF) (http://www.gbif.es/ipt) was used both to upload the Darwin Core Archive and to fill out the metadata.
The Darwin Core elements for the occurrence data included in the dataset were: occurrenceId, modified, language, basisOfRecord, institutionCode, collectionCode, catalogNumber, scientificName, kingdom, phylum, class, order, family, genus, specificEpithet, scientificNameAuthorship, continent, country, countryCode, stateProvince, county, locality, minimumElevationInMeters, maximumElevationInMeters, decimalLongitude, decimalLatitude, coordinateUncertaintyinMeters, geodeticDatum, recordedBy, day, month, year, EventDate.
For the measurement data, the Darwin Core elements included were: occurrenceId, measurementID, measurementType, measurementValue, measurementAccuracy, measurementUnit, measurementDeterminedDate, measurementDeterminedBy, measurementMethod.
Quality control description: The sampling transects were georeferenced using a hand held GPS device (WGS 84 Datum) with an accuracy of କ m. We also used colour digital orthophotographs provided by the Andalusian Cartography Institute and GIS (ArcGIS 9.2 ESRI, Redlands, California, USA) to verify that the geographical coordinates of the transects were correct (Chapman and Wieczorek 2006).
For field identification, several field guides were used (De Juana and Varela 2000, Jonsson 2001). The scientific names were checked with database of the IOC World Bird List (v 5.52) (Gill and Donsker 2015). We also used the R package taxize (Chamberlain and Szocs 2013, Chamberlain et al. 2014) to verify the taxonomical classification.
In addition, we performed validation procedures (Chapman 2005a, 2005b) (geopraphic coordinate format, coordinates within country/provincial boundaries, absence of ASCII anomalous characters in the dataset) with DARWIN_TEST (v3.2) software (Ortega-Maqueda and Pando 2008).
The data behind mysterious bird deaths in New Mexico
Last week, the Rocky Mountain states experienced a strong storm that brought with it snow, near hurricane force winds, and unseasonable record-breaking cold temperatures. In Albuquerque on September 8, it was sunny and a record-high 96ºF. The next afternoon, a severe windstorm tore through the region. The Albuquerque airport measured windspeed of over 70 mph, and temperatures plummeted to historic lows. Albuquerque broke a 100-year record low temperature when the mercury dropped to 40ºF. While snowfall was heaviest in the northern Rockies from Montana to Colorado, New Mexico received several inches of heavy, wet snow as far south as the Sandia Mountains east of Albuquerque.
Migratory bird casualties in Velarde, NM on 13 Sep 2020. Image from video posted on Twitter by Austin Fisher.
My colleagues and I spent the morning of Thursday 10 September picking up dead birds in the Sandias. We found several dead Empidonax flycatchers of three species, a Vesper Sparrow, and a Townsend’s Warbler. Some birds were wet from the overnight snow, but others were completely dry, huddled in the corners of buildings. A Dusky Flycatcher sat dazed in the parking lot.
We first thought little of it: mortality is expected for migratory birds, and we didn’t find more than a handful of carcasses. But social media told a grimmer story that night. We read reports of widespread mortalities across the state: dead swallows along a bike path in Albuquerque, a half-dozen Empidonax flycatchers and swallows in one park in Clovis, and a local news report of 300 carcasses recovered by researchers from New Mexico State University and nearby White Sands Missile Range. It was soon apparent that a significant mortality event had occurred.
But one video on Twitter recorded by local journalist Austin Fisher stood out to me: several dozen swallows dead in an arroyo in Velarde, approximately 40 miles north of Santa Fe. It was only when I reached out to Austin for the purposes of this report that I realized the video wasn’t taken the week before during the cold snap, but rather the previous night, on 13 September. To see it for myself, fellow ornithology grad student, Nick Vinciguerra, and I drove the hour and a half north that night.
When we arrived at midnight, we found a macabre scene. Several hundred Violet-green Swallows were strewn across the bank of the Rio Grande. Dozens of birds had stuffed themselves into the few natural cavities, and many more were dead amongst the vegetation. In total, we found 305 individuals of six species, all of which were insectivores: 258 Violet-green Swallows, 35 Wilson’s Warblers, six Bank Swallows, two Cliff Swallows, one Northern Rough-winged Swallow, a MacGillivray ’ s Warbler, and two Western Wood-Pewees. These proportions are similar to what was reported by researchers at NMSU.
Nick Vinciguerra collecting Violet-green Swallows on the banks of the Rio Grande River at midnight in Velarde, NM.
Several hypotheses are emerging to explain this mass mortality event in New Mexico. Recently, heightened attention has been given to the possibility that historic wildfires across western North America are to blame, and wildfires certainly pose a major disruption to migratory birds. For instance, a wildfire could cause birds to flee an area before they’ve replenished their fat stores. Indeed, anecdotal reports from banding stations suggest that wildfires contribute to unusual migrant influxes into areas that are free from fire. Michael Hilchey, a volunteer bander at the Rio Grande Bird Research Station in Albuquerque, noted a significantly higher volume of migrants over the past two weeks than has been over the last 10–15 years. Smoke is covering nearly all of the lower 48 states, and while we experienced heavy smoke in Albuquerque the night before the storm arrived, fires are not new or unexpected during the height of fall migration. Indeed, wildfires are common and increasing in frequency.
There is, I believe, a much more plausible reason for large numbers of birds to die during migration: lack of food.
The 55–60ºF temperature swing observed in New Mexico combined with hurricane force winds and with wet snow very likely caused hypothermia in some birds, especially juveniles. Furthermore, cold temperatures also affect the food supply for insectivores, as insects (which become dormant or dead) are then covered by snow. Certainly, they are not flying through the air, as swallows and pewees need. Dave Leatherman, a former entomologist for the state of Colorado, noted marked behavioral differences in foraging insectivorous birds during the week’s snowstorm. In addition, a 2007 study by Ian Newton found that unseasonably cold weather can have a negative effect on migrating birds. While cold temperatures and snow cut off the food supply for naïve migrants, resident birds not stressed by migration typically have both fat reserves and local knowledge of where to find shelter.
Notably, and understandably, this type of die-off commonly affects swallows. In several documented cases of swallow mortality events (Newton 2007), a sudden drop in temperatures caused insects to become dormant (and stop flying). In Kazakstan during the fall of 2000, cold and snow killed thousands of Barn Swallows (Berezovikov and Anisimov 2002). Severe cold snaps in 1931 and 1974 killed “hundreds of thousands, possibly millions” of swallows and martins in central Europe (Alexander 1933, Ruge 1974, Bruderer and Muff 1979, Reid 1981, Newton 2007). Specifically, Newton (2007) states, “When short of food in cold weather, swallows and swifts often seek shelter in buildings, huddle together for warmth, and may suffer from hypothermia and starvation. Other migratory insectivores also die in such conditions, but less conspicuously.”
The 305 individuals laid out at the Museum of Southwestern Biology that Nick Vinciguerra and I collected from Velarde, NM on 14 Sep 2020. All individuals will be deposited as specimens in the museum’s Bird Division for future research and education.
Sudden and dramatic unavailability of food caused by a historic and drastic cold snap is, I believe, a more parsimonious explanation than a widespread, smoke induced, mass mortality event. While we do not have data on how fast smoke inhalation would kill birds hundreds of miles away from the fires themselves, what we do have are data from the 258 Violet-green Swallows that Nick and I collected in Velarde this week.
Satellite imagery showing smoke from wildfires in the western U.S. on 9 Sep 2020. Image © NOAA.
If a lack of food contributed to the mortality event, birds would have less fat and no protection against hypothermia. Indeed, of the hundreds of birds we assessed, none had fat stores on their bodies. Furthermore, many birds also showed signs of breast muscle atrophy, which points to starvation and dehydration. The average mass of an adult male Violet-green Swallow is 14.4 g females are slightly lighter at 13.9 g. In addition, I used an open-access museum collections database, Vertnet, to find data on thirty specimens collected July–September, and their average weight was 15 g. We weighed 234 swallows which showed only minor signs of decomposition, and their average mass was dramatically lighter: 9.5 g, or about two-thirds the weight of normal birds. Though we have yet to perform any toxicology analyses or inspect their lungs for signs of smoke inhalation, I think it is safe to say that these birds were starved and succumbed to hypothermia. When USFWS autopsies of other birds are reported in the coming weeks or months, we suspect they will reveal a similar cause of death.
Christopher Witt, Professor at UNM and Director of the Museum of Southwestern Biology, waxed poetical with me this week about how fall 2020 has brought a spectacular array of fall migrants to Albuquerque, noting that it’s been the “Best I’ve seen in years.” As a birder myself, I also benefitted from this better than average migration with my lifer Blackpoll Warbler on the University of New Mexico campus this week. Our influx of migrants may or may not have been due to wildfires, but I have no doubt that they were affected by the extreme cold and high winds in New Mexico. Though the fires and extreme weather events are influenced by human-induced climate change, it is unlikely that the wildfires alone caused the death of thousands of birds in New Mexico.
A comparison of body mass from the birds we salvaged on 14 September 2020 with that of other Violet-green Swallows collected during fall migration across the North America, downloaded from Vertnet, an open access biodiversity database. Both outlier points on the right refer to specimens that had little to no fat stores.
Higher elevation birds sport thicker down 'jackets' to survive the cold
Sahas Barve, a Peter Buck Fellow at the Smithsonian's National Museum of Natural History, led a new study to examine feathers across 249 species of Himalayan songbirds, finding that birds living at higher elevations have more of the fluffy down--the type of feathers humans stuff their jackets with--than birds from lower elevations. Published on Feb. 15 in the journal Ecography, the study also finds that smaller-bodied birds, which lose heat faster than larger birds, tend to have longer feathers in proportion to their body size and thus a thicker layer of insulation. Credit: Suniti Bhushan Datta
Feathers are a sleek, intricate evolutionary innovation that makes flight possible for birds, but in addition to their stiff, aerodynamic feathers used for flight, birds also keep a layer of soft, fluffy down feathers between their bodies and their outermost feathers to regulate body temperature.
Using the Smithsonian's collection of 625,000 bird specimens, Sahas Barve, a Peter Buck Fellow at the Smithsonian's National Museum of Natural History, led a new study to examine feathers across 249 species of Himalayan songbirds, finding that birds living at higher elevations have more of the fluffy down—the type of feathers humans stuff their jackets with—than birds from lower elevations. Published on Feb. 15 in the journal Ecography, the study also finds that smaller-bodied birds, which lose heat faster than larger birds, tend to have longer feathers in proportion to their body size and thus a thicker layer of insulation.
Finding such a clear pattern across so many species underscores how important feathers are to a bird's ability to adapt to its environment and suggests that adding down may be a strategy common to all songbirds, or passerines as they are known to researchers. Furthermore, finding that birds from colder environments tend to have more down may one day help researchers predict which birds are most vulnerable to climate change simply by studying their feathers.
"The Himalayas are seeing some of the fastest rates of warming on Earth," Barve said. "At the same time, climate change is driving an increase in the frequency and intensity of extremely cold events like snowstorms. Being able to accurately predict the temperatures a bird can withstand could give us a new tool to predict how certain species might respond to climate change."Using the Smithsonian's collection of 625,000 bird specimens, Sahas Barve, a Peter Buck Fellow at the Smithsonian's National Museum of Natural History, led a new study to examine feathers across 249 species of Himalayan songbirds, finding that birds living at higher elevations have more of the fluffy down--the type of feathers humans stuff their jackets with--than birds from lower elevations. Published on Feb. 15 in the journal Ecography, the study also finds that smaller-bodied birds, which lose heat faster than larger birds, tend to have longer feathers in proportion to their body size and thus a thicker layer of insulation. Carla Dove, who runs the museum's Feather Identification Lab and contributed to the study, said she was excited to work together with Barve to use the Smithsonian's collections in a new way. "Sahas looked at more than 1,700 specimens. Having them all in one place in downtown Washington, D.C., as opposed to having to go to the Himalayas and study these birds in the wild, obviously makes a big difference. It allowed him to gather the data he needed quickly before the COVID lockdowns swept the globe, and then work on the analysis remotely." Credit: Chip Clark, Smithsonian.
The research was inspired by a tiny bird called a goldcrest during a frigid morning of field work in the Sho-kharkh forest of the Himalayas. Barve found himself wondering how this bird, which weighs about the same as a teaspoon of sugar, was able to flit about the treetops in icy air that was already numbing his fingers. Shoving his hands back into the pockets of his thick down jacket, the question that formed in Barve's mind was "Do Himalayan birds wear down jackets?"
To answer that question, Barve and his co-authors used a microscope to take photos of the chest feathers of 1,715 specimens from the Smithsonian's collections representing 249 species from the cold, high-altitude Himalayan Mountains. Then, Barve and his co-authors used those super-detailed photos to determine exactly how long each feather's downy section was relative to its total length. The team was able to do that by looking at the fluffy downy section of each feather close to its base when compared to the streamlined ends of most birds' feathers.
After meticulously logging the relative lengths of all those downy sections, Barve analyzed the results and found that the smallest birds and the birds from the highest elevations, where temperatures are at their coldest, tended to have the highest proportion of down on their body feathers. The analysis showed that high-elevation birds had up to 25% more down in their feathers, and the smallest bird had feathers that were three times as long as the largest birds, proportionately to their body size.
Past research suggested that birds from colder habitats sported added downy insulation, but Barve said this is the first study to analyze this pattern for such a large number of species in cold environments and across 15,000 feet of elevation.Barve led a new study to examine feathers across 249 species of Himalayan songbirds, finding that birds living at higher elevations have more of the fluffy down--the type of feathers humans stuff their jackets with--than birds from lower elevations. Published on Feb. 15 in the journal Ecography, the study also finds that smaller-bodied birds, which lose heat faster than larger birds, tend to have longer feathers in proportion to their body size and thus a thicker layer of insulation.The research was inspired by a tiny bird called a goldcrest during a frigid morning of field work in the Sho-kharkh forest of the Himalayas. Barve found himself wondering how this bird, which weighs about the same as a teaspoon of sugar, was able to flit about the treetops in icy air that was already numbing his fingers. Shoving his hands back into the pockets of his thick down jacket, the question that formed in Barve's mind was "Do Himalayan birds wear down jackets?" Credit: Jennifer Renteria
"Seeing this correlation across so many species makes our findings more general and lets us say these results suggest all passerine birds may show this pattern," Barve said. "And we never would have been able to look at so many different species and get at this more general pattern of evolution without the Smithsonian's collections."
Carla Dove, who runs the museum's Feather Identification Lab and contributed to the study, said she was excited to work together with Barve to use the Smithsonian's collections in a new way. "Sahas looked at more than 1,700 specimens. Having them all in one place in downtown Washington, D.C., as opposed to having to go to the Himalayas and study these birds in the wild, obviously makes a big difference. It allowed him to gather the data he needed quickly before the COVID lockdowns swept the globe, and then work on the analysis remotely."
Barve said he is following up this study with experiments looking into just how much insulation birds get from their feathers and then will tie that to the feather's structure and proportion of down. One day, Barve aims to develop a model that will allow scientists to look at the structure of a feather and predict how much insulation it gives the bird—a capability that could help researchers identify species vulnerable to climate change.
Dove said the potential to use these results to eventually understand how some birds might cope with climate change highlights the importance of museum collections. "We have more than 620,000 bird specimens collected over the past 200 years waiting for studies like this. We don't know what our specimens will be used for down the line that's why we have to maintain them and keep enhancing them. These specimens from the past can be used to predict the future."