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- July 6, 2011
- 09:00 AM
- 635 views
Study Confirms Importance of Red Knot Migratory Stopovers
by John Beetham in A DC Birding Blog
As many readers know, Red Knots (Calidris canutus rufa) are in serious trouble.* Though they were once an abundant shorebird during spring migration on the Atlantic Coast, their population crashed in the 1990s. This winter, Red Knots suffered another setback, when a third of their current known population disappeared from the wintering grounds for reasons that are not entirely clear. The major crash in the 1990s has long been linked to food availability at migratory stopover sites.... Read more »
McGowan, Conor P., James E. Hines, James D. Nichols, James E. Lyons, David R. Smith, Kevin S. Kalasz, Lawrence J. Niles, Amanda D. Dey, Nigel A. Clark, Philip W. Atkinson, Clive D. T. Minton, and William Kendall. (2011) Demographic consequences of migratory stopover: linking red knot survival to horseshoe crab spawning abundance. Ecosphere, 2(art69). info:/10.1890/ES11-00106.1
- June 2, 2010
- 09:00 AM
- 950 views
Why You Should Record All Species and Bird Outside Hotspots
by John Beetham in A DC Birding Blog
Accurate species distribution data is necessary to address biodiversity challenges. To save endangered species, conservationists need to know which species populations are contracting or expanding. Restoring an ecosystem requires an accurate picture of how the ecosystem existed historically. Unfortunately, existing global data collections such as the Global Biodiversity Information Facility and IUCN Red List underrepresent some geographic areas, especially in the tropics, and may not show accurate distribution or trends for many species that live there. A further problem with newer datasets is that conservation organizations have focused largely on endangered species and nature reserves and lack the broad baseline data that may be necessary for future conservation problems.A new study measures how well existing data compilations cover the Galliformes, an order that is well-studied and contains many threatened species. The datasets surveyed included museum collections, scientific articles, banding records, bird atlases, and birders' trip reports (archived on sites such as travellingbirder.com). Museum collections are the most significant source of historical distribution data, and scientific literature has gained importance over time. Birding reports are a relatively new phenomenon and still account for relatively few records, with most of those coming from birding hotspots.Geographic coverage of different data sources: A) museums, B) literature, C) banding, D) atlases, and E) website trip reports The data sources vary in how much geographic area they cover. Museum collections are the most comprehensive as a whole, though individual collections may be more localized. Scientific literature covers western Europe, China, and southern Asia well, but not as many studies are available for other regions. Banding data and atlases were largely confined to western Europe. Birding trip reports provide broader coverage than banding or atlases but are concentrated in well-known hotspots and easily accessible locations. Because active specimen collecting has declined, contemporary data sources are less geographically comprehensive than older ones (see maps below).Records for all galliform species across the Indian Subcontinent from A) pre-1930 and B) 1990–2006The authors offer three suggestions for improving the geographic coverage and usability of biodiversity data:Museum collections and sightings data from scientific literature should be catalogued in electronic databases to make historical data more accessible.*Observation records should include a date and location, preferably with geographic coordinates, and be incorporated into a central database to avoid fragmentation.Observers should report all species rather than just rare or threatened ones and should look outside of known biodiversity hotspots.They see a role for citizen science projects to monitor biodiversity and cite eBird specifically as an example of how a citizen science project should collect data from users. From their perspective, its principal strengths include requiring users to enter a date and geotagged location, flagging unusual records for review by regional editors, and encouraging participants to submit checklists from areas with few observations. Unfortunately eBird has so far been limited to the Americas (though it will expand coverage soon) and only records bird observations. The authors hope, however, that eBird's model can be expanded to other taxa, even less charismatic ones.* Though the authors do not cite it specifically, the North American Bird Phenology Program still needs volunteers to scan and transcribe thousands of historical observations.Boakes, E., McGowan, P., Fuller, R., Chang-qing, D., Clark, N., O'Connor, K., & Mace, G. (2010). Distorted Views of Biodiversity: Spatial and Temporal Bias in Species Occurrence Data PLoS Biology, 8 (6) DOI: 10.1371/journal.pbio.1000385Posted on A DC Birding Blog under a Creative Commons 3.0 License.... Read more »
Boakes, E., McGowan, P., Fuller, R., Chang-qing, D., Clark, N., O'Connor, K., & Mace, G. (2010) Distorted Views of Biodiversity: Spatial and Temporal Bias in Species Occurrence Data. PLoS Biology, 8(6). DOI: 10.1371/journal.pbio.1000385
- May 8, 2010
- 09:00 AM
- 1,237 views
How Far Can a Bird Fly Nonstop During Migration?
by John Beetham in A DC Birding Blog
Bar-tailed Godwits / Image: Phil Battley Recent studies using satellite telemetry or geolocators have shown that some bird species are capable of very long nonstop flight during migration, far longer than previously thought. Some of the longest belong to Bar-tailed Godwits, which have been tracked performing nonstop flights of over 11,000 km (or about 7,000 miles). Ruddy Turnstones perform similarly impressive flights. A new study in PLoS Biology tries to measure whether there are any limits to nonstop flights.How long a bird is able to fly depends on a few factors. First, it needs to be able to use fuel efficiently. Bar-tailed Godwits do this very well, burning only 0.42% of their body mass per hour of flight. Ruddy Turnstones, Greater Knots, and Blackpoll Warblers have slightly lower efficiency. Flight speed is also important. Bar-tailed Godwits and Blackpoll Warblers have similar fuel efficiency, but a Bar-tailed Godwit can fly twice as far without stopping because it flies more quickly (see graph below). A faster bird will not only fly farther on the same fuel supply but also will be less likely to be blown off course by turbulence.Potential flight range for the bar-tailed godwit (blue curve) and the blackpoll warbler (red curve). Other factors that may influence long-distance flight include body shape and energy consumption. A long-distance migrant must be able to carry sufficient fuel supplies for the flight but do so in a very streamlined body. One way that godwits achieve this is by eliminating unnecessary organ mass and burning muscle mass in the latter stages of a migration flight. Other shorebirds share this trait.A few other species like Sharp-tailed Sandpiper might attempt similar flights, but the Earth imposes its own limit on how far a bird might need to migrate. There are relatively few combinations of wintering grounds and breeding grounds that would require such a long nonstop flight. Some Pectoral Sandpipers breed in Central Asia and winter in South America, but they break up their migration into two stages. Arctic Terns have a longer trip (24,000 km!) but can feed along the way. It seems that the Bar-tailed Godwit's 11,000 km is about as far as a bird is likely to fly without stopping to feed.Hedenström, A. (2010). Extreme Endurance Migration: What Is the Limit to Non-Stop Flight? PLoS Biology, 8 (5) DOI: 10.1371/journal.pbio.1000362Posted on A DC Birding Blog under a Creative Commons 3.0 License.... Read more »
Hedenström, A. (2010) Extreme Endurance Migration: What Is the Limit to Non-Stop Flight?. PLoS Biology, 8(5). DOI: 10.1371/journal.pbio.1000362
- February 23, 2010
- 09:00 AM
- 1,074 views
Meat on a String: A Possible Limit to Corvid Intelligence?
by John Beetham in A DC Birding Blog
Common Raven / USFWS Photo Corvids – crows, ravens, jays, and magpies – are well known to be among the most intelligent of birds. Along with parrots, corvids have been a frequent subject of avian intelligence studies. Experiments have documented problem-solving and tool use, both in the lab and in the wild. Many of the recent experiments have tested intelligence in New Caledonian Crows (Corvus moneduloides), but tests of Ravens (Corvus corax) and Rooks (Corvus frugilegus) have also found problem-solving capabilities. New Caledonian Crows are a common subect for research because they are known to use a variety of tools in the wild.A classic test of bird intelligence involves a piece of food dangling at the end of a string. Multiple bird species can figure out through trial and error how to retrieve the food by pulling the string. Corvids and psittacids retrieve the food so quickly that researchers have suggested that these birds may solve the problem at an advanced level. That is, instead of relying on trial and error, these birds might be able to picture a solution in their minds. Experiments with Ravens and Keas (Nestor notabilis) have provided some hints of advanced problem-solving, but the birds have difficulty retrieving food at the end of a string if the string is crossed by another of the same color.A new PLoS ONE article takes the intelligence tests a step further with New Caledonian Crows. Once again, a piece of meat is suspended at the end of a string. This time, however, the reward is screened from view by a piece of plywood with a small hole in it – just wide enough to pull the meat through. If a crow goes under the board, it can see the food and string. From above the board, it can still see the reward through the hole, but not well enough to judge its distance or whether pulling the string is moving the meat closer. The image shows the setup for this study; this image shows examples of prior experiments. Successful retrieval would require pulling the string part way, stepping on the portion pulled, and then pulling the rest of the string.When this problem (A) was presented to four crows that already had some experience retrieving meat on strings, the crows were able to solve the problem, but with difficulty. The experienced crows made more mistakes and took longer to arrive at a solution. Naïve crows – ones with no experience of string problems – had a much harder time. One naïve crow was able to complete the task (A) after five trials; the other three naïve crows pulled or pushed the string but never used the pull-step action necessary for completing the task. Another group of four naïve crows was presented with the same problem, but this time with a mirror that showed the result of pulling the string (B). Two of the crows completed the task after a few attempts, but the other two never figured out the solution. The article includes video of crows presented with simple and screened string problems.The results of this study suggest that crows learn to solve problems through a combination of visual feedback and prior experience with related problems. When crows have an unobstructed view of the string and the meat, they can see the meat get closer each time they pull the string and step on it. Without that visual feedback, they can still solve the problem if they remember that pulling on the string works. This supports the idea that crows solve problems mainly through trial and error and not by insight or causal reasoning. However, the study is not conclusive since one naïve crow did solve the problem and naïve crows that had the benefit of a mirror did not all find the solution.It seems that researchers have found a limit to corvid intelligence. Even if they do not have the benefit of causal reasoning, crows and ravens still best other bird species at the string pulling problem. Some finches can complete a simple string-pulling task but have a much higher error rate, and many finches never figure out the solution. Even naïve crows, however, can solve the simple string problem almost immediately. Their larger forebrains may allow corvids to process and act on visual feedback more quickly than birds in other families.Taylor, A., Medina, F., Holzhaider, J., Hearne, L., Hunt, G., & Gray, R. (2010). An Investigation into the Cognition Behind Spontaneous String Pulling in New Caledonian Crows PLoS ONE, 5 (2) DOI: 10.1371/journal.pone.0009345Posted on A DC Birding Blog under a Creative Commons 3.0 License.... Read more »
Taylor, A., Medina, F., Holzhaider, J., Hearne, L., Hunt, G., & Gray, R. (2010) An Investigation into the Cognition Behind Spontaneous String Pulling in New Caledonian Crows. PLoS ONE, 5(2). DOI: 10.1371/journal.pone.0009345
- February 21, 2010
- 09:00 AM
- 1,188 views
House Finches, Disease, and Bird Feeders
by John Beetham in A DC Birding Blog
House Finches at a Feeder Like humans, birds can be infected by various diseases, some of which can be quite contagious. Among feeder birds, House Finches are particularly susceptible to Mycoplasmal conjunctivitis. Avian conjunctivitis causes very noticeable changes to a bird's appearance and behavior. Infected birds appear to have swollen or crusty eyes. Becoming lethargic, they succumb more easily to starvation or predation.A new study examines behaviors that may encourage the spread of conjunctivitis among House Finches. Researchers placed healthy finches into the middle chamber of a partitioned cage with a healthy finch on one side and a visibly diseased finch on the other; all three finches were of the same sex. Food dishes were placed at the edge of each chamber so that the middle finch would have to interact with neighboring finches in order to feed. The researchers then monitored the behavior of the middle finch. While female House Finches fed equally near healthy or diseased finches, males strongly preferred to feed near a diseased finch. This preference may be explained by the symptoms of conjunctivitis. Since the disease produces lethargy, infected males are much less likely to challenge a healthy male for dominance at a feeding station. Feeding near infected individuals thus reduces the energy and social costs of losing such a confrontation. The danger, of course, is that feeding and other interactions with infected individuals is likely to increase a healthy bird's chances of catching disease. Mycoplasmal conjunctivitis is a relatively new disease among House Finches, first documented in 1994. In the context of such a new and contagious disease, male finches' instinct to reduce confrontation may work against their ability to resist disease.Bouwman, K., & Hawley, D. (2010). Sickness behaviour acting as an evolutionary trap? Male house finches preferentially feed near diseased conspecifics Biology Letters DOI: 10.1098/rsbl.2010.0020Posted on A DC Birding Blog under a Creative Commons 3.0 License.... Read more »
Bouwman, K., & Hawley, D. (2010) Sickness behaviour acting as an evolutionary trap? Male house finches preferentially feed near diseased conspecifics. Biology Letters. DOI: 10.1098/rsbl.2010.0020
- February 18, 2010
- 09:00 AM
- 1,121 views
Iron in the Beaks of Birds
by John Beetham in A DC Birding Blog
Birders know well that birds migrate – the cycle of bird movements keeps birding interesting throughout the year. Many landbird migration routes are well-documented, and even some over-water routes are starting to be determined. What is less understood is how the birds know where they are going. Recent research has focused on how birds might sense, or even see, the Earth's magnetic field for orientation. At least one recent study proposed that some birds use an olfactory sense for guidance. Visual cues, such as the stars for nocturnal migrants or waterways for diurnal migrants, have also been proposed.One new study finds iron-containing cells in the upper beaks of birds. Three years ago, the same research team reported that the upper beaks of homing pigeons contain iron minerals arranged in structures that could allow a pigeon to sense a magnetic field. This study found similar structures in the beaks of three other bird species: Garden Warbler (Sylvia borin), European Robin (Erithacus rubecula), and domestic chickens (Gallus gallus). Prussian blue stained dendrites in the inner lining of the upper beak of (A) homing pigeon, (B) garden warbler, (C) European robin, and (D) domestic chicken. (E) General semi-schematic drawing of an iron containing dendrite. (F) Axon bundle with several iron containing dendrites.In all four species, the iron-rich dendritic cells are located near the top of the upper beak and not in the lower beak or in any other tissue. The iron particles are arranged in narrow rod-like clusters, which appear to lie parallel to one another. The clusters are connected to the ophthalmic nerve, so they form part of a bird's sensory system. The iron minerals contained in the dendritic cells appear to be maghemite (Fe(III)2O3) rather than magnetite (Fe (II)Fe(III)2O4), but the sample was too small to determine that conclusively. Given that such similar clusters are present in several bird species that are not closely related, including a nonmigratory bird, they may be present in many more (or even all) bird species, and an important part of avian direction-finding abilities.Falkenberg, G., Fleissner, G., Schuchardt, K., Kuehbacher, M., Thalau, P., Mouritsen, H., Heyers, D., Wellenreuther, G., & Fleissner, G. (2010). Avian Magnetoreception: Elaborate Iron Mineral Containing Dendrites in the Upper Beak Seem to Be a Common Feature of Birds PLoS ONE, 5 (2) DOI: 10.1371/journal.pone.0009231Posted on A DC Birding Blog under a Creative Commons 3.0 License.... Read more »
Falkenberg, G., Fleissner, G., Schuchardt, K., Kuehbacher, M., Thalau, P., Mouritsen, H., Heyers, D., Wellenreuther, G., & Fleissner, G. (2010) Avian Magnetoreception: Elaborate Iron Mineral Containing Dendrites in the Upper Beak Seem to Be a Common Feature of Birds. PLoS ONE, 5(2). DOI: 10.1371/journal.pone.0009231
- January 26, 2010
- 09:00 AM
- 582 views
Dunlin Lose Weight to Avoid Peregrines
by John Beetham in A DC Birding Blog
Dunlin at Surf Beach in California / Photo by Alan VernonA new paper based on studies from the Fraser River estuary in British Columbia finds that hunting pressure from Peregrine Falcons (Falco peregrinus) is changing the behavior of Pacific Dunlin (Calidris alpina pacifica). The peregrine population crashed forty years ago, primarily thanks to pesticides, and has since rebounded. All of those new falcons need to eat, and shorebirds are suitable prey because of their size, numbers, and penchant for foraging and loafing in open spaces. Shorebirds have to adopt evasive behaviors to avoid being eaten.One way of avoiding predation is to move to areas without much raptor activity. Some dunlin do this by finding safer roosting locations away from where peregrines are hunting, even if it means flying longer distances to reach them. Others utilize a behavior known as "over-ocean flocking": during high tides, they fly out to sea and remain in flight there for an extended period of time. This behavior was rarely noted by observers prior to the late 1990s, but since then it has been observed regularly. According to daily observations from January 2006, "over-ocean flocking" occurred on 15 out of 17 days, and dunlin spent an average 2.8 hours over the ocean at a time.Most shorebirds build up their body fat reserves to avoid starvation during the winter. The extra weight helps them survive when food supplies are low, but has the trade-off of making it more difficult to escape predators in flight. In the face of increased predation, shorebirds like dunlin will need to carry less body fat to avoid becoming prey. According to bird banding data, that is exactly what happened when peregrines rebounded. Data from the 1970s shows that dunlin mass builds quickly and remains high through November and December before falling in January and February. By the 1990s, the average autumn peak weight had fallen by about 4 grams, or about 7% of their historical peak body mass.This study is a good example of how conservation actions to benefit one species can have unintended results elsewhere in the ecosystem. In this case, the increased presence of peregrines around coastal areas is forcing dunlin to change their feeding and roosting behaviors.Ydenberg, R., Dekker, D., Kaiser, G., Shepherd, P., Evans Ogden, L., Rickards, K., & Lank, D. (2010). Winter body mass and over-ocean flocking as components of danger management by Pacific dunlins BMC Ecology, 10 (1) DOI: 10.1186/1472-6785-10-1Posted on A DC Birding Blog under a Creative Commons 3.0 License.... Read more »
Ydenberg, R., Dekker, D., Kaiser, G., Shepherd, P., Evans Ogden, L., Rickards, K., & Lank, D. (2010) Winter body mass and over-ocean flocking as components of danger management by Pacific dunlins. BMC Ecology, 10(1), 1. DOI: 10.1186/1472-6785-10-1
- January 14, 2010
- 09:00 AM
- 20,527 views
What Makes Birds Cooperate Against Predators?
by John Beetham in A DC Birding Blog
Pied Flycatcher / Photo by Simon Eugster via WikimediaMany bird species are known to cooperate to mob and scold predators such as hawks, owls, or outdoor cats. In North America this behavior is probably most noticeable among jays and crows since they form the loudest mobs. Chickadees and titmice likewise gather to scold a predator when one is found. Other species may participate or use their own cooperative actions to confuse and drive away predators. The general strategy is to gather around a predator and scold while moving around just out of striking distance until the predator becomes frustrated and departs.It is clear that cooperation benefits prey species. Most predators of birds rely to some degree on surprise, and if one or more birds is drawing attention to a predator's presence, that advantage is gone. Predators also need to be also to focus their attacks precisely, something difficult to do while a lot of noisy birds are flying around nearby. However, it is not obvious why birds would evolve such behaviors. If you consider evolution in terms of competition for resources and survival, it may be in the self-interest of some birds to see other birds culled from the population. Mobbing also exposes individual birds to some risk; if one strays too close to a targeted predator, it could easily be injured or killed.So what drives some species to cooperate to fend off predators instead of hunkering down and hiding? One group of researchers decided to test whether the risk of predation influenced birds' willingness to mob predators. To do so they studied the reactions of Pied Flycatchers (Ficedula hypoleuca) to dummy predators near their nests during breeding season.The researchers provided paired nestboxes to attract breeding flycatchers to their study site. Only pairs in which both nestboxes were occupied were used in the study. Once the birds were settled into the nestboxes, researchers trained the birds for five days. Some pairs of nests were presented with a stuffed Tawny Owl (Strix aluco) and playback of Pied Flycatcher alarm calls to condition them to expect a high risk of predation. Other nests received a visit from a stuffed Mistle Thrush (Turdus viscivorus) so that they would expect lower risk.In the experiments, the researchers placed the stuffed Tawny Owl on a platform near each of the nestbox pairs with the owl facing one of the nests. This time there was no audio playback so that the flycatchers would have to find it themselves, and the owl was presented to both the high-risk and low-risk groups. Researchers then watched from a blind to see if birds from the neighboring nest would assist the ones whose nest was threatened. Markings on the trees around the nestboxes allowed the minimum approach distance to be measured from the blind. After 10 minutes of mobbing the stuffed owl was removed, and then an hour later the experiment was repeated with the other nestbox in the pair.Minimum approach distance from the stuffed owl by nest owners and neighbouring flycatchers. Source: Proc. R. Soc. B 22 February 2010 vol. 277 no. 1681 513-518 doi: 10.1098/rspb.2009.1614 As one might expect, the owners of the nest directly under threat had the most intense reaction to the stuffed predator. In fact, the nestbox owners in the high-risk and low-risk groups differed little in their responses. However, we do see a difference in the reactions of flycatchers from the neighboring nestboxes. Among the high-risk group, neighbors always came to the assistance of the nestbox pairs, versus 61.5% of the time in the low-risk group. Neighboring birds from the high-risk group also mobbed more intensely than neighbors from the low-risk group, although in both cases the neighbors reacted less intensely than the nestbox owners. When the tests were repeated an hour later, the results were similar.For Pied Flycatchers, at least, the increased risk of predation encourages neighboring nesting pairs to cooperate to remove one threat to their success. This may happen through learned reciprocity. Alarm by one nest owner might attract the attention of other nesters, and their reactions might encourage the first nest owner to come to their assistance in turn. The authors further suggest that other types of cooperative behavior might have a similar origin in risky environments.Krams, I., Berzins, A., Krama, T., Wheatcroft, D., Igaune, K., & Rantala, M. (2009). The increased risk of predation enhances cooperation Proceedings of the Royal Society B: Biological Sciences, 277 (1681), 513-518 DOI: 10.1098/rspb.2009.1614Posted on A DC Birding Blog under a Creative Commons 3.0 License.... Read more »
Krams, I., Berzins, A., Krama, T., Wheatcroft, D., Igaune, K., & Rantala, M. (2009) The increased risk of predation enhances cooperation. Proceedings of the Royal Society B: Biological Sciences, 277(1681), 513-518. DOI: 10.1098/rspb.2009.1614
- January 7, 2010
- 09:00 AM
- 1,176 views
Evaluating State Endangered Species Lists
by John Beetham in A DC Birding Blog
Long-billed Curlew / Photo by Mike BairdAt a time when federal listings have been delayed and international standards are difficult to implement, state endangered species lists can play an important role in protecting at-risk species. That is, they can protect globally threatened species, especially ones for which their region bears high responsibility. Jeffrey Wells of the Boreal Songbird Initiative set out to assess how well state lists are identifying and protecting globally threatened species and the results were published this week as an article in PLoS ONE, "Global versus Local Conservation Focus of U.S. State Agency Endangered Bird Species Lists."In the United States, 48 states maintain their own lists of species that are endangered, threatened, or of special concern. Wells uses 47 of these lists (excluding Hawaii) and divides the species into four categories based on their global risk of extinction and the degree to which a state bears responsibility for its global population. Global risk is based on assessments produced by Partners in Flight.Percent of each state's E-T-SC bird species in each of four risk-responsibility categories. doi:10.1371/journal.pone.0008608.g002The results show that states are effective at protecting those species that are at risk globally and for which states bear high responsibility. States also give protections to some species that are not at risk globally but are concentrated in their region. However, they also put a lot of effort into protecting secure but locally uncommon species that may not need help as much as the others. For example, state lists include such species as Double-crested Cormorant (2 states), Great Egret (12 states), Laughing Gull (2 states), Bank Swallow (3 states), Magnolia Warbler (2 states), and Dark-eyed Junco (3 states). Meanwhile, some globally threatened species are getting ignored, even when states bear some responsibility for maintaining that global population. Lesser Prairie-Chicken, Long-billed Curlew, Bendire's Thrasher, and Golden-winged Warbler are all listed in half or less of the states that comprise their ranges. Since none of them are federally listed either, those four receive no legal protections in the U.S. apart from what the Migratory Bird Treaty Act offers. My state, New Jersey, lists Savannah Sparrow (locally uncommon) but not Saltmarsh Sparrow (globally at-risk).To a certain extent, it is not really the job of state wildlife agencies to assess and protect based on global risk. That is a task that should belong to the federal government, which has greater resources and more connections to international wildlife agencies for cooperation. However, many globally at-risk species fail to reach even the federal endangered list, let alone benefit from conservation actions. (According to Wells, 16 bird species listed on the IUCN Redlist are not present on the U.S. federal list.) In that context, perhaps states should take a greater role in protecting species based on their global risk of extinction, rather than local criteria. Wells, J., Robertson, B., Rosenberg, K., & Mehlman, D. (2010). Global versus Local Conservation Focus of U.S. State Agency Endangered Bird Species Lists PLoS ONE, 5 (1) DOI: 10.1371/journal.pone.0008608Posted on A DC Birding Blog under a Creative Commons 3.0 License.... Read more »
Wells, J., Robertson, B., Rosenberg, K., & Mehlman, D. (2010) Global versus Local Conservation Focus of U.S. State Agency Endangered Bird Species Lists. PLoS ONE, 5(1). DOI: 10.1371/journal.pone.0008608
- December 24, 2009
- 09:00 AM
- 1,336 views
Twisting Genitals and Forced Copulation: The Strange Sex Lives of Ducks
by John Beetham in A DC Birding Blog
A few years ago, a study explored the strange genitals of waterfowl and found that females typically had complex vaginas if males of the same species had complex phalluses. Waterbirds are among the few bird species that have phalluses at all. Duck species in the Anas, Clangula, and Oxytura genera take this to an extreme, with very long, twisting genitals, sometimes equipped with spines. Phalluses twist counterclockwise, and vaginas twist clockwise. (You can see some examples at the post linked above.) Other duck species have shorter and simpler reproductive organs.Adding such complexity into the reproductive tract seems odd at first glance, since it would seem to impede fertilization. The research team, led by Patricia Brennan, hypothesized that female ducks evolved complex vaginas to counteract forced copulation, a behavior that is well-documented in waterfowl. (See here and this infamous case.) A twisting vagina could give females more control over which males fertilized their eggs.The same research team is back with more evidence that female ducks evolved vaginas to deter forced insemination. To test their hypothesis, the researchers studied domesticated muscovy ducks at a farm in California. They placed male ducks in a cage to mate with a female but made the males ejaculate into a glass tube instead. A total of 56 males were videotaped in the process of erection and ejaculation. The male ducks at the farm had been trained to provide semen for commercial breeding and were thus amenable to the testing procedure.Duck genitalia and mechanical barriers. (a) Male and female genitalia in a Pekin duck (Anas sp.). The male phallus (right) spirals in a counterclockwise direction and the female oviduct (left) spirals in a clockwise direction. The female vagina has blind pouches (b.p.) proximal to the cloacal entrance, followed by a series of spirals (sp.). s.s., sulcus spermaticus; a. ph., tip of the penis; cl, cloaca. Scale bar, 2 cm. (b) Diameter glass tubes (10 mm) of different shapes used to test male penis eversion; from left to right, straight, anticlockwise (male-like), clockwise and 135° bend (female-like). Male ducks are unusual not only in having phalluses but also in erecting them only after mounting a female. A phallus then curves as it erects to match the shape of the receiving vagina or, in the case of this study, the glass tubes. The researchers tested three different types of tubes. The first type, as a control, was a straight glass tube; the second type had a counterclockwise twist, just like a phallus. Neither of these presented an obstacle to erection. The third type imitated the shapes of vaginas, with either a clockwise twist or a 135° bend. The latter tubes either blocked phalluses at the entrance or caused them to erect in the wrong direction. You can see video of erections into the various tube shapes as a data supplement to the paper.Males encountering a clockwise or bent tube shape could still ejaculate. However, if they were copulating with an unreceptive female duck, their sperm would be left near the entrance of the reproductive tract where they would be less likely to cause fertilization. Willing females, on the other hand, may increase the chances of fertilization by adopting a receptive posture and contracting and relaxing their cloacal muscles to allow easier erection. In that way, a female duck could still produce offspring with the male of her choice, not just whichever male happened to be the most aggressive.New study:Brennan, P., Clark, C., & Prum, R. (2009). Explosive eversion and functional morphology of the duck penis supports sexual conflict in waterfowl genitalia Proceedings of the Royal Society B: Biological Sciences DOI: 10.1098/rspb.2009.2139Older study:Brennan, P., Prum, R., McCracken, K., Sorenson, M., Wilson, R., & Birkhead, T. (2007). Coevolution of Male and Female Genital Morphology in Waterfowl PLoS ONE, 2 (5) DOI: 10.1371/journal.pone.0000418Posted on A DC Birding Blog under a Creative Commons 3.0 License.... Read more »
Brennan, P., Clark, C., & Prum, R. (2009) Explosive eversion and functional morphology of the duck penis supports sexual conflict in waterfowl genitalia. Proceedings of the Royal Society B: Biological Sciences. DOI: 10.1098/rspb.2009.2139
Brennan, P., Prum, R., McCracken, K., Sorenson, M., Wilson, R., & Birkhead, T. (2007) Coevolution of Male and Female Genital Morphology in Waterfowl. PLoS ONE, 2(5). DOI: 10.1371/journal.pone.0000418
- November 30, 2009
- 09:00 AM
- 1,501 views
A Historic Paper on Cuckoo Behavior
by John Beetham in A DC Birding Blog
In the coming year, the Royal Society is entering its 350th year of existence. It was founded on November 28, 1660, as a forum for scientists and philosophers to discuss their work. Since 1665, it has published the journal Philosophical Transactions. To celebrate its anniversary, the Royal Society is posting sixty of the most significant papers from Philosophical Transactions. You can find them at the society's Trailblazing website. Nestled among the other historic papers is one that concerns birds. In 1788, Edward Jenner reported his observations of Common Cuckoos (Cuculus canorus).... Read more »
Jenner, E. (1788) Observations on the Natural History of the Cuckoo. By Mr. Edward Jenner. In a Letter to John Hunter, Esq. F. R. S. Philosophical Transactions of the Royal Society of London (1776-1886), 78(1), 219-237. DOI: 10.1098/rstl.1788.0016
- November 25, 2009
- 09:00 AM
- 1,376 views
How Raptor Talons Fit Their Prey
by John Beetham in A DC Birding Blog
Most birders learn through field guides that different raptor groups have recognizable body shapes adapted to the way they hunt. Accipiters, for example, have short rounded wings and long tails to facilitate short pursuits through close quarters. This is, in fact, a key to identifying many raptors in the field. Close study of raptors reveals even more subtle anatomical differences. A newly published article in PLoS ONE relates differences in the shapes of raptor talons to how they kill their prey.... Read more »
Fowler, D., Freedman, E., & Scannella, J. (2009) Predatory Functional Morphology in Raptors: Interdigital Variation in Talon Size Is Related to Prey Restraint and Immobilisation Technique. PLoS ONE, 4(11). DOI: 10.1371/journal.pone.0007999
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