Coots reject alien offspring

New research has revealed that American Coots not only have a remarkable ability to recognise strange eggs in their nests but will also reject chicks from other coots which hatch in their nests.

Biologists at the University of California, Santa Cruz, discovered in 2003 that American Coots can count their own eggs and throw out ones which have been laid in their nests by other coots. Now new findings, published in Nature, show that coot parents can tell the difference between their own chicks and any impostors that manage to hatch in their nest. Any impostor recognised is usually violently rejected.

Lees meer: Birdwatch

How hazardous is the Sahara Desert crossing for migratory birds? Indications from satellite tracking of raptors

Auteurs: Roine Strandberg, Raymond H.G. Klaassen, Mikael Hake, Thomas Alerstam
Bron: BIOLOGY LETTERS online December 2, 2009, doi: 10.1098/rsbl.2009.0785
Abstract: We investigated the risk associated with crossing the Sahara Desert for migrating birds by evaluating more than 90 journeys across this desert by four species of raptors (osprey Pandion haliaetus, honey buzzard Pernis apivorus, marsh harrier Circus aeruginosus and Eurasian hobby Falco subbuteo) recorded by satellite telemetry. Forty per cent of the crossings included events of aberrant behaviours, such as abrupt course changes, slow travel speeds, interruptions, aborted crossings followed by retreats from the desert and failed crossings due to death, indicating difficulties for the migrants. The mortality during the Sahara crossing was 31 per cent per crossing attempt for juveniles (first autumn migration), compared with only 2 per cent for adults (autumn and spring combined). Mortality associated with the Sahara passage made up a substantial fraction (up to about half for juveniles) of the total annual mortality, demonstrating that this passage has a profound influence on survival and fitness of migrants. Aberrant behaviours resulted in late arrival at the breeding grounds and an increased probability of breeding failure (carry-over effects). This study also demonstrates that satellite tracking can be a powerful method to reveal when and where birds are exposed to enhanced risk and mortality during their annual cycles.

Activational effects of odours on avian navigation

Auteurs: Paulo E. Jorge, Paulo A.M.Marques, John B. Phillips
Bron: PROCEEDINGS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES 277 (1678): 45-49 JAN 7 2010
Abstract: The sensory basis of the navigational map remains one of the most important and intriguing questions in animal behaviour. In birds, odours have been hypothesized to provide the primary source of map information. Convincing tests have shown that experienced homing pigeons rely on map information obtained at sites where they are exposed to natural odours, even if subsequently released (without additional olfactory information) at a different site. These findings have been interpreted as support for the olfactory map hypothesis.
Using this ‘false-release-site’ (FRS) approach, we compared the effects of exposure to natural odours with that of exposure to a series of artificial odours lacking spatial information. Our findings show that olfactory exposure to either natural or artificial odours at an FRS
caused pigeons to rely on map information obtained at the FRS, even if subsequently released at the true-release site in the opposite direction from the home loft. Because artificial odours did not provide map information, however, the findings clearly demonstrate that olfactory exposure provides no navigational information to pigeons whatsoever; instead it activates an independent non-olfactory map system. This test decisively contradicts the olfactory map hypothesis, which predicts that olfactory cues are the primary source of navigational information used by birds.

By Feeding the Birds, You Could Change Their Evolutionary Fate

Feeding birds in winter is a most innocent human activity, but it can nonetheless have profound effects on the evolutionary future of a species, and those changes can be seen in the very near term. That's the conclusion of a report published online on December 3rd in Current Biology, showing that what was once a single population of birds known as blackcaps has been split into two reproductively isolated groups in fewer than 30 generations, despite the fact that they continue to breed side by side in the very same forests.

The reproductive isolation between these populations, which live together for part of the year, is now stronger than that of other blackcaps that are always separated from one another by distances of 800 kilometers or more, the researchers said.

Lees meer: Science Daily

De ene gans is de andere niet

"Ganzen hebben een persoonlijkheid. En die persoonlijkheid is van invloed op hoe ze foerageren. Dat toont Ralf Kurvers van de Resource Ecology Group aan."

De ene gans is de andere niet. Dat klinkt banaal, maar is het niet. 'Doorgaans wordt aangenomen dat ieder dier vrij is om te kiezen wat-ie wil. In modellen die simuleren hoe beesten zich over een landschap verspreiden wordt er altijd van uitgegaan dat elk dier gelijk is. Maar daar vind ik geen bewijs voor', zegt bioloog en aio Kurvers.
Integendeel zelfs: persoonlijkheid speelt een rol. En dat blijkt uit de proeven met brandganzen die hij doet bij het NIOO in Heteren. Persoonlijkheid betekent in dit geval of een gans consistent bepaald gedrag vertoont. Kurvers richt zich daarbij op de variatie tussen individuen en op de manier waarop de ganzen informatie verzamelen. Kort gezegd: gaan ze zelf op zoek of kijken ze af? Ganzen die zelf op zoek gaan zijn dapper of doortastend ('bold'), ganzen die afkijken zijn afwachtend ('shy').

Lees meer: Resource [Wetenschap]

First Evidence For A Second Breeding Season Among Migratory Songbirds

Biologists for the first time have documented a second breeding season during the annual cycle of five songbird species that spend summers in temperate North America and winters in tropical Central and South America.

It was known that these species, which migrate at night when there are fewer predators and the stars can guide their journey, breed during their stay in temperate regions of the United States and Canada.

But it turns out that they squeeze in a second breeding season during a stopover in western Mexico on their southward migration, said Sievert Rohwer a University of Washington professor emeritus of biology and curator emeritus of birds at the Burke Museum of Natural History and Culture at the UW.

Lees meer: Science Daily

Falcon’s migration tracked

The mystery of the migration of the Eleanora's Falcon has been unravelled for the first time by a research team using satellite tracking to map its route between Europe and Africa.

Their findings, published recently in the journal Zoological Studies, show that the bird flies more than 9,500 kilometres across the African continent from the Balearic Islands in the Mediterranean to the island of Madagascar. Other secrets now revealed include that fact that these falcons migrate by both day and night, and cross supposed ecological barriers such as the Sahara Desert.

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Birds Line Nests with Natural Antibacterials

Some birds add bits of aromatic plants, such as lavender, mint, or yarrow, to their nests. The garlands serve not as air fresheners or décor, but rather, it is thought, as pesticides against such parasites as fleas and blowfly larvae, which commonly vex chicks. Yet various experiments have failed to confirm that quite reasonable idea. Now Adèle Mennerat, her former graduate adviser Marcel M. Lambrechts of the National Center for Scientific Research in Montpellier, France, and several colleagues say scientists may have been off track—bacteria could be the targeted affliction.

Lees meer: LiveScience

Black Rat Does Not Bother Mediterranean Seabirds

Human activities have meant invasive species have been able to populate parts of the world to which they are not native and alter biodiversity there over thousands of years. Now, an international team of scientists has studied the impact of the black rat on bird populations on Mediterranean islands. Despite the rat's environmental impact, only the tiny European storm petrel has been affected over time by its enforced cohabitation with the rat.

A European team has studied around 300 islands in the western Mediterranean, and has confirmed that the presence of the black rat (Rattus rattus) has an effect on the number of marine birds there. Mass colonisation by rats is damaging to the native biota of islands, leading to a 68% risk of extinction for procellariiforme seabirds (tube-nosed birds with webbed feet of three to four toes).

Lees meer: ScienceDaily

Lowly females pick mediocre mates

Low-quality females prefer low-quality males, at least in the avian world.

This is according to research published in the Royal Society journal Proceedings B, testing female zebra finches' taste in males.

As adults, the low-quality females showed a preference for the songs of males of the same quality, and for the male birds themselves.

Evolutionary biologists previously thought that females would always opt for the best male available.

Lees meer: BBC NEWS | Science & Environment

Male songbirds provide indirect parental care by guarding females during incubation

Auteurs: Bradley C. Fedy, Thomas E. Martin
Bron: BEHAVIORAL ECOLOGY, Volume 20, Number 5 p. 1034-1038
Abstract: Across many taxa, guarding of fertile mates is a widespread tactic that enhances paternity assurance. However, guarding of mates can also occur during the nonfertile period, and the fitness benefits of this behavior are unclear. Male songbirds, for example, sometimes guard nonfertile females during foraging recesses from incubation. We hypothesized that guarding postreproductive mates may have important, but unrecognized, benefits by enhancing female foraging efficiency, thereby increasing time spent incubating eggs. We tested the hypothesis in 2 songbird species by examining female behavior during natural and experimentally induced absences of males. Male absence caused increased vigilance in foraging females that decreased their efficiency and resulted in less time spent incubating eggs. Male guarding of nonfertile females can thus provide a previously unrecognized form of indirect parental care.

Breeding systems, climate, and the evolution of migration in shorebirds

Auteurs: Gabriel E. García-Peña, Gavin H. Thomas, John D. Reynolds, Tamás Székely
Bron: BEHAVIORAL ECOLOGY 2009 20(5):1026-1033; doi:10.1093/beheco/arp093
Abstract: Migratory behavior incurs energetic costs that may influence the time
and energy available for reproduction including territory
establishment, courtship, pair formation, incubation, and brood care.
Conversely pair formation and parental care may leave less time and
energy available for migration and other nonbreeding behaviors.
Therefore, natural selection favoring migratory behavior may influence
breeding system evolution and vice versa. We used phylogenetic
comparative methods to investigate relationships between migration
distance and the wide diversity of breeding systems in shorebirds
(sandpipers, plovers and allies). Consistent with previous studies, we
show that long-distance migration is associated with reduced male care
across shorebird species. We then use directional phylogenetic analyses
to test whether migration distances have tended to increase or decrease
over time and whether such evolutionary changes have preceded or
followed changes in parental care. We show that evolutionary
transitions from short-distance migration to long-distance migration
have coevolved with changes from full biparental care to reduced male
care. Furthermore, our directional analyses suggest that increments in
migration distance are more likely to have preceded reductions in male
care than vice versa. We also show that male polygamy is associated
with northern breeding latitudes when the nonbreeding latitude is
controlled statistically. Although this suggests that mating systems,
parental care, and migration have more complex relationships than
previously thought, our results are consistent with the hypothesis that
migration influences breeding system evolution.

Albatross Camera Reveals Fascinating Feeding Interaction With Killer Whale

Scientists from British Antarctic Survey, National Institute of Polar Research, Tokyo, and Hokkaido University, Japan, have recorded the first observations of how albatrosses feed alongside marine mammals at sea.

A miniature digital camera was attached to the backs of four black-browed albatrosses (Thalassarche melanophrys) breeding at colonies on Bird Island, South Georgia in the Southern Ocean. Results are published online this week in the open-access journal PLoS ONE from the Public Library of Science.

Lees meer: ScienceDaily
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Wind farms cause bird declines

A new study of UK wind farms suggests that numbers of several breeding birds of decline close to the wind turbines which would make their appropriate siting even more important.

The study took place on uplands where several species of high conservation concern breed. Twelve major upland wind farms were surveyed six times during the breeding season for a dozen common species including Golden Plover, Lapwing, Curlew, Snipe, Red Grouse, Common Buzzard, Hen Harrier, Kestrel, and Skylark, Meadow Pipit, Stonechat and Wheatear.

The results, published in the Journal of Applied Ecology, should help developers planning renewable energy projects by offering greater certainty as to likely impacts so that they can quickly progress acceptable proposals in appropriate locations by avoiding important areas for birds. If wind farms are sited inappropriately in areas where these vulnerable birds breed at high densities, then those populations may subsequently decline.

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Birds unveil 'silver wings'

Some birds have silver wings, created by a previously unknown structure in their feathers, scientists have discovered.
A delicate arrangement of barbules creates a silver sheen upon otherwise dark feathers.
The effect is different to the usual iridescence that adds colour to the plumage of many birds.

Pelicans, ducks, vultures and cranes all possess these silver wings, which might indicate a bird's fitness.

Lees meer: BBC - Earth News

Migrating Birds Chill To Fatten Up

Marathon runners are famed for pasta packing in the days before a big run but when tiny passerine birds set out on their epic migrations, the distances are too great to cover on the energy reserves with which they embark.

Michał Wojciechowski and Berry Pinshow explain that most birds stop off en route to their destination to refuel. One of the Eurasian blackcaps' preferred refuelling stops is Midreshet Ben-Gurion, Israel, where the birds fill up on fruit and insects before setting off again. Knowing that birds expend twice as much energy during stopovers than they use in transit, the duo wondered whether the tiny aviators drop their body temperature at night during stopovers to save energy and build up their reserves faster.

Lees meer: ScienceDaily

Arctic geese winter further north

The winter distribution of an Arctic goose has shifted northwards as climate has warmed over the last 40 years, with birds once wintering in Mexico now staying in Alaska.

Studies have shown that, until recently, nearly the entire population (90 per cent) of Pacific Black Brant spent the winter in Mexico. Now as many as to 30 per cent are choosing to spend their winters in Alaska instead. Fewer than 3,000 geese were detected wintering in Alaska before 1977, and this has now jumped to as many as 40,000 birds.

Lees meer: Birdwatch

Why do birds participate in mixed-species foraging flocks? A large-scale synthesis

Auteurs: Hari Sridhar, Guy Beauchamp, Kartik Shanker
Bron: ANIMAL BEHAVIOUR, Volume 78, Issue 2, August 2009, Pages 337-347
Abstract: Mixed-species flocks of foraging birds have been documented from terrestrial habitats all over the world and are thought to form for either improved feeding efficiency or better protection from predators. Two kinds of flock participants are recognized: those that join other species ('followers') and are therefore likely to be the recipients of the benefits of flock participation and those that are joined ('leaders'). Through comparative analyses, using a large sample of flocks from around the world, we show that (1) 'followers' tend to be smaller, more insectivorous, and feed in higher strata than matched species that participate in flocks to a lesser extent and (2) 'leaders' tend to be cooperative breeders more often than matched species that are not known to lead flocks. Furthermore, meta-analyses of published results from across the world showed that bird species in terrestrial mixed-species flocks increase foraging rates and reduce vigilance compared to when they are solitary or in conspecific groups. Moreover, the increase in foraging rates is seen only with flock followers and not flock leaders. These findings suggest a role for predation in the evolution of mixed-species flocking. Species that are vulnerable to predation follow species whose vigilance they can exploit. By doing so, they are able to reduce their own vigilance and forage at higher rates.

Trans-Sahara migrants select flight altitudes to minimize energy costs rather than water loss

Auteurs: Heiko Schmaljohann, Felix Liechti, Bruno Bruderer
Bron: BEHAVIORAL ECOLOGY AND SOCIOBIOLOGY, Volume 63, Number 11 / September, 2009
Abstract: Meteorological conditions influence strongly the energy and water budget of birds. By adjusting their flights spatially and temporally with respect to these conditions, birds can reduce their energy expenditure and water loss considerably. By radar, we quantified songbird migration across the western Sahara in spring and autumn. There autumn migrants face the trade-off between (a) favorable winds combined with hot and dry air at low altitudes and (b) unfavorable winds combined with humid and cold air higher up. Thus, it can be tested whether birds may chose altitudes to minimize water loss instead of energy expenditure.
We predicted optimal flight altitudes with respect to water loss and energy expenditure based on a physiological flight model when crossing the western Sahara and compared these model predictions spatially and temporally with measured songbird densities. The model aiming for minimal water consumption predicted a mean flight altitude of 3,400 m under autumn conditions.
However, 64% of the nocturnal songbird migration flew at altitudes below 1,000 m above ground level profiting from tailwind. This preference for tailwind in autumn, despite the hot and dry air, emphasizes the importance of energy savings and diminishes the significance of possible water stress for the selection of flight altitude. Nevertheless, during daytime, high energy expenditure due to air turbulences and water loss due to warmer air and direct solar radiation prevent songbirds from prolonging their nocturnal flights regularly into the day. Birds crossing the Sahara save water by nocturnal flights and diurnal rests.

Great tits acquire taste for bats

A Hungarian cave has turned out to be a larder of highly unusual food for great tits: hibernating pipistrelle bats.

Over two winters, researchers found the birds were systematically hunting bats by sight and sound as they hibernated through the cold months.

Writing in the journal Biology Letters, the scientists say this is the first proof of bat-hunting in songbirds.

Great tits usually dine on smaller prey such as insects and seeds, with bat-eating probably very rare.

The researchers found the birds preferred other food when they could get it.

Lees meer: BBC News

Skylarks recognise neighbours

New research shows that Skylarks are able to distinguish between the songs of their neighbours and those of strangers, who may pose a threat, enabling them to readily see off any intruders.

Scientists from Queen Mary, University of London studied the songs of Skylarks and compared their structure. They found that the songs of neighbouring Skylarks share more syllables with one other than they do with those of strangers, rather like a dialect.

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Birds use fatal fragrances

Highly aromatic plants are often used in birds' nests and new research has demonstrated that these fatal fragrances are particularly chosen to kill off bacteria that would otherwise infect the nestlings.

Biologists studied the nests of Blue Tits on Corsica which
are known to incorporate fresh fragments of aromatic plants when building them.
Previous research has shown that this does not reduce infestation by nest
ectoparasites, but does improve growth and condition of chicks at fledging.


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Bird's Tool Use Called 'Amazing'

Just like in Aesop's fable, scientists now find that crows might indeed learn to drop stones in pitchers to raise the height of water inside, in this case to bring a tasty, floating worm within reach.

This suggests the fanciful millennia-old tale might actually have been based on fact.

In Aesop's fable, "the crow and the pitcher," a thirsty crow dropped stones in a pitcher to raise the water level and quench its thirst. Past experiments have shown that crows and their relatives — altogether known as corvids — are indeed "remarkably intelligent, and in many ways rival the great apes in their physical intelligence and ability to solve problems," said researcher Christopher Bird at the University of Cambridge in England.

Lees meer: Live Science

'Feather-eating bugs' dull birds

Brightly coloured birds can become infected with bacteria that eat their feathers.

That in turn can affect the health of the birds and dull their plumage.

The discovery comes from a study that found that 99% of all Eastern bluebirds surveyed in Virginia, US were infected with feather-degrading bacteria.

Such bacteria were first discovered a decade ago, but the latest research is the best evidence yet that the bugs affect the colour and health of birds.

Lees meer: BBC Earth News

Bird Population Declines In Northern Europe Explained By Thiamine (Vitamin B1) Deficiency

Wild birds of several species are dying in large numbers from a paralytic disease with hitherto unknown cause in the Baltic Sea area. A research team at Stockholm University, Sweden, led by Associate Professor Lennart Balk, has demonstrated strong relationships between this disease, breeding failure, and advanced thiamine (vitamin B1) deficiency in eggs, young, and adults.

Lees meer: ScienceDaily

Foraging in precocial chicks of the black-tailed godwit Limosa limosa: vulnerability to weather and prey size

Auteurs: Hans Schekkerman, Arjan Boele
Bron: JOURNAL OF AVIAN BIOLOGY, Volume 40 Issue 4, Pages 369-379
Abstract: Self-feeding precocial development is associated with high energy requirements and potentially vulnerable to short-term reductions in food availability, yet few studies have investigated development of foraging in precocial chicks and its sensitivity to environmental conditions. We studied time budgets and foraging behaviour during the 25-d prefledging period in the insectivorous chicks of a grassland shorebird, the black-tailed godwit Limosa limosa. Until 8–10  d old, parental brooding was the main determinant of chicks' daily foraging time. Brooding decreased with age and temperature and increased during rainfall. Foraging time increased to 70–90% of the daylight period in chicks older than a week, during which distances of 3–12  km  d−1 were covered. Chicks took 98% of their arthropod prey from the grassland vegetation. Prey ingestion rates increased in the first week and slowly declined thereafter, modified by wind speed, temperature and time of day. Chicks in poor body condition were brooded more than chicks growing normally and hence had less feeding time, potentially leading to a negative condition spiral under adverse conditions. However, we found no effect of condition on prey ingestion rate that would preclude recovery when conditions improve. Combining behavioural observations with data on energy expenditure revealed that mean prey size was small (1–4.5  mg), necessitating a high feeding rate, but increased notably after 7–10  d of age. This coincided with a decrease in walking speed, suggesting that chicks fed more selectively. Prey of older chicks approached the upper limit of sizes available in exploitable densities in the grassland vegetation, and this enhances the chicks' sensitivity to variation in prey availability due to weather and agricultural practice.

Huge declines in woodland birds

The nightingale has effectively vanished from woodlands across the UK.

A 30-year survey of British woodland birds has found that its population has fallen by more than 95%.

Seventeen other bird species have also declined significantly, many of which overwinter in tropical west Africa where their habitat is being destroyed.

Numbers of starling, linnet, bullfinch and willow warbler all crashed, while 12 species, including the blackcap, magpie and collared dove, increased.

These startling trends in the populations of some of the UK's best known woodland birds comes from the British Trust for Ornithology's (BTO) Common Bird Census, which gathered data on 49 species between 1967 and 1999.

Lees meer: BBC News

Birds With A Nose For A Difference: Avoidance Of Inbreeding In Birds Demonstrated

Avoidance of inbreeding is evident amongst humans, and has been demonstrated in some shorebirds, mice and sand lizards. Researchers writing in the open access journal BMC Evolutionary Biology now report that it also occurs in a strictly monogamous species of bird, suggesting that the black-legged kittiwake possesses the ability to choose partners with a very different genetic profile.

Lees meer: ScienceDaily

Oldest bird's nest found

The world's oldest bird of prey nest that is still in use has been discovered in Greenland but climate change may threaten its continuing use, believe ornithologists.

Gyr Falcons will reuse a successful nest for thousands of years. Photo: Derek Bakken (Wikimedia commons)

Many birds of prey use traditional nest sites year after year. To find out just how long some nests have been in use, ornithologists in Greenland carbon dated the guano and other debris around Gyr Falcon nests. 

Three other nests, each over 1,000 years old, have also been found, one of which contains feathers from a bird that lived more than 650 years ago. But one nest from central-west Greenland beat these being between 2,360 and 2,740 years old.

Lees meer: Birdwatch

How an Airplane-Sized Bird Replaced Its Feathers

An extinct bird the size of a Cessna airplane and weighing as much as an average human was one of the largest birds to have ever flown the friendly skies.

Scientists have wondered how the bird, called Argentavis magnificens, could balloon to such heft (more than 150 pounds, or 70 kg) and still replace its feathers during a molt. Now, new research reveals the bird, which lived 6 million years ago in the Miocene epoch, likely molted all of its feathers at once during a long fast.

The finding derives from a larger study that figures out a strange limiting factor to maximum body size in birds — the amount of time it takes to replace flight feathers.

Lees meer: LiveScience

Bird Migrations Set To Increase: Added Distance Is 'Considerable Threat' To Some Species

Bird migrations are likely to get longer according to the first ever study of the potential impacts of climate change on the breeding and winter ranges of migrant birds. The length of some migrations could increase by as much as 400 km. "The predicted future temperature changes and the associated changes in habitat could have serious consequences for many species", said lead-author Nathalie Doswald of Durham University (UK).

Lees meer: Science Daily

What decision rules might pink-footed geese use to depart on migration? An individual-based model

Auteurs: Olivier Duriez, Silke Bauer, Anne Destin, Jesper Madsen, Bart A. Nolet, Richard A. Stillman, Marcel Klaassen
Bron: BEHAVIORAL ECOLOGY, Volume 20, Number 3
Abstract: Decisions taken during migration can have a large effect on the fitness of birds. Migration must be accurately timed with food availability to allow efficient fueling but is also constrained by the optimal arrival date at the breeding site. The decision of when to leave a site can be driven by energetics (sufficient body stores to fuel flight), time-related cues (internal clock under photoperiodic control), or external cues (temperature, food resources). An individual based model (IBM) that allows a mechanistic description of a range of departure decision rules was applied to the spring migration of pink-footed geese (Anser brachyrhynchus) from wintering grounds in Denmark to breeding grounds on Svalbard via 2 Norwegian staging sites. By comparing predicted with observed departure dates, we tested 7 decision rules. The most accurate predictions were obtained from a decision rule based on a combination of cues including the amount of body stores, date, and plant phenology. Decision rules changed over the course of migration with the external cue decreasing in importance and the time-related cue increasing in importance for sites closer to breeding grounds. These results are in accordance with descriptions of goose migration, following the "green-wave": Geese track the onset of plant growth as it moves northward in spring, with an uncoupling toward the end of the migration if time is running out. We demonstrate the potential of IBMs to study the possible mechanisms underlying stopover ecology in migratory birds and to serve as tools to predict consequences of environmental change.

Reproduction of the common buzzard at its northern range margin under climatic change

Auteurs: Aleksi Lehikoinen, Patrik Byholm, Esa Ranta, Pertti Saurola, Jari Valkama, Erkki Korpimäki, Hannu Pietiäinen and Heikki Henttonen
Bron: OIKOS, Volume 118 Issue 6, Pages 829 - 836
Abstract: A changing climate induces shifts in the location of biomes. Tracing such a shift may pose problems for life history traits adapted to the prior conditions, so that, e.g. the timing of reproduction and the time with sufficient resources for rearing hatchlings do not match. We show that the timing of breeding of Finnish common buzzards Buteo buteo, has advanced with over ten days as a response to the warming of early spring, during 1979–2004. During the same period the isoclines of the onset of breeding have moved about 200 km to the north-east. However, the reproductive performance of the common buzzard has not increased as a response to these changes. Despite increasing temperatures during early spring, the temperatures of early summer have remained the same since the 1970s. Combined, the early onset of breeding and the unchanged temperatures of early summer have lead to decreased post-hatching temperatures. Under these circumstances, common buzzard offspring now face a higher risk to hatch into less favourable weather conditions than three decades ago. Furthermore, summer precipitation, harmful for nestlings, has been predicted to increase in the future, thus possibly further worsening the circumstances for breeding common buzzards. Our results demonstrate that even if common buzzards in Finland breed at the northern limit of the species' distribution, and could therefore be expected to gain advantage from a warming climate, the opposite is the case.

Tuning towards tomorrow? Common nightingales Luscinia megarhynchos change and increase their song repertoires from the first to the second breeding season

Auteurs: Sarah Kiefer, Christina Sommer, Constance Scharff, Silke Kipper and Roger Mundry
Bron: JOURNAL OF AVIAN BIOLOGY, Volume 40 Issue 2, Pages 231-236
Abstract: In many oscines, song repertoire size correlates with male quality and female mate choice, and can vary with age. In a cross-sectional field study in common nightingales Luscinia megarhynchos, one y old birds had substantially smaller repertoires than did older ones. In laboratory experiments males can acquire new song types during this period. This longitudinal field study therefore investigates whether individual nightingales increase their repertoires from the first to the second breeding season.
We report a striking repertoire turnover, with an average overall increase of 24% of the first season's repertoire, resulting from added and dropped song types (54% and 30%, respectively). The number of added song types correlated positively with the size of the first season's repertoire. These results are consistent with the notion that repertoire size in nightingales correlates with male quality, although the overlap between repertoire sizes of first and second season birds makes it impossible to discriminate age based solely on repertoire size. Comparing the number of song types an individual sang in both seasons ('permanent song types') revealed a lower overlap than reported for subsequent seasons. The frequencies with which these were sung in the first season were less predictive of how often they were sung in the second season than was the case between later years.
This drastic repertoire turnover from the first to the second season may be a selective process in response to the local song types, constrained by genetic makeup and shaped by early experience.

Why Female Birds Seek Extra Mates: Study Of Blue Tits Fuels Debate

When female birds mate with males other than their social partners and have broods of mixed paternity, the offspring sired by these "extra-pair" fathers may often get a head start in life, according to a new report. The discovery adds fuel to the debate about why some female birds seek those extra mates in the first place.

The report is published online on April 30th in Current Biology, a Cell Press publication.

"A diverse range of explanations have been proposed to account for female participation in extra-pair copulations," said Michael Magrath of University of Groningen, The Netherlands. "The explanations that have received most attention suggest that females stand to gain genetically superior offspring by having their eggs fertilized by males that are of higher genetic quality or that are genetically more compatible."


Lees meer: ScienceDaily

Differential responses of red knots, Calidris canutus, to perching and flying sparrowhawk, Accipiter nisus, models

Auteurs: Kimberley J. Mathot, Piet J. van den Hout, Theunis Piersma
Bron: ANIMAL BEHAVIOUR, Volume 77, Issue 5, May 2009, Pages 1179-1185
Abstract: According to the threat-sensitive predator avoidance hypothesis, prey should match the intensity of their antipredation response to the degree of threat posed by predators. We used controlled indoor experiments to investigate the ability of red knots to discern between high- and low-threat encounters with a representative predator, the sparrowhawk.
The behaviour of knots was compared across three conditions: no predators present (very low predation threat), presentation of a perching sparrowhawk model (low predation threat) and presentation of a gliding sparrowhawk model (high predation threat). In all behavioural parameters measured, red knots showed evidence of discriminating between the different levels of predation risk. Knots responded immediately to the presence of sparrowhawks with escape flights, and the duration of escape flights was longer following the gliding sparrowhawk events than following perching events. Similarly, the proportion of time spent vigilant increased with increasing level of predation threat, while the proportion of time spent feeding decreased.
These results show that knots recognize variations in the level of predation threat, and adjust their antipredator responses accordingly. Furthermore, model sparrowhawks were introduced into the experimental arena at similar distances to the knots, which suggests that knots are able to use cues other than distance to predator to gauge the immediate level of threat that a predator poses.

Owls change colour

Climate change is having a direct effect on the plumage of some birds, according to new research from Italy. The red form of Scops Owl has become commoner than the grey form.

The Scops Owl can be found in two main colour morphs, one dull grey and the other rusty red. Grey birds survive better in years when the climate is cool and dry, while red birds thrive in warm, wet conditions.


Lees meer: Birdwatch

Sparrows solve problems more quickly in larger groups

For many animals, living with others has obvious benefits. Social animals can hunt in packs, gain safety in numbers or even learn from each other. In some cases, they can even solve problems more quickly as a group than as individuals. That's even true for the humble house sparrow - Andras Liker and Veronika Bokony from the University of Pannonia, Hungary, found that groups of 6 sparrows are much faster at opening a tricky bird feeder than pairs of birds.

After ruling out several possible explanations, the duo put the speedy work of the bigger flock down to their greater odds of including boffin birds. Individual sparrows vary greatly in terms of their skills, experiences and personalities. Larger groups are more likely to include the sharpest bird brains, or several diverse individuals whose abilities complement each other.


Lees meer: Not Exactly Rocket Science

The importance of pre-thicket conifer plantations for nesting Hen Harriers Circus cyaneus in Ireland

Auteurs: MARK W. WILSON, SANDRA IRWIN, DAVID W. NORRISS, STEPHEN F. NEWTON, KEVIN COLLINS, THOMAS C. KELLY, JOHN O'HALLORAN
Bron: IBIS Volume 151 Issue 2, Pages 332 - 343
Abstract: Hen Harriers Circus cyaneus are threatened across much of their range and their conservation requires appropriate habitat management. The locations of 148 Hen Harrier nests found in the Republic of Ireland during national breeding surveys in 2000 and 2005 were used to assess nest-site selection. The distribution of these nests was compared to distributions of randomly located points to investigate selection at the scale of the nest-site and landscape. The main nesting habitats selected were pre-thicket stage of first and, particularly, second rotation plantations, mostly of exotic conifers.
There was no evidence that the area of post-closure plantations negatively affected Hen Harrier nest distribution. There was a positive correlation across study areas between changes in numbers of Hen Harrier nests between 2000 and 2005 and changes in the area of pre-thicket second rotation plantations over the same period. The overall effect of plantation forests on breeding Hen Harriers in Ireland therefore appears to be positive.
However, this study did not consider the effects of plantation habitats on breeding success. Improved grassland was strongly avoided as a nesting habitat.
Furthermore, after controlling for the influence of nesting habitat on nest location, landscapes with a high percentage cover of improved grassland were also avoided. Further agricultural intensification of grassland in areas where Hen Harriers breed is likely to have a negative impact on this species.
These results are required for the development of management strategies for the conservation of this species.

Diet specificity is not associated with increased reproductive performance of Golden Eagles Aquila chrysaetos in Western Scotland

Auteurs: D. P. WHITFIELD, ROBIN REID, PAUL F. HAWORTH, MIKE MADDERS, MICK MARQUISS, RUTH TINGAY, ALAN H. FIELDING
Bron: IBIS, Volume 151 Issue 2, Pages 255 - 264
Abstract: Amongst raptor species, individuals with specialized diets are commonly observed to have higher reproductive output than those with general diets. A suggested cause is that foraging efficiency benefits accrue to diet specialists. This diet specificity hypothesis thus predicts that diet breadth and reproductive success should be inversely related within species. We highlight, however, that a prey availability hypothesis also makes the same prediction in some circumstances. Hence, when high diet specificity results from high encounter rates with an abundant, preferred prey, then prey availability may affect reproductive success, with diet specialization as an incidental correlate.
Using three insular study areas in western Scotland, we examine diet specificity and reproductive success in Golden Eagles Aquila chrysaetos. Diet breadth and breeding productivity were not negatively related in any of our study areas, even though birds with specific diets did tend to have a higher incidence of preferred prey (grouse and lagomorphs) in the diet. Indeed, in two study areas there was evidence that diet generalists had higher breeding productivity. Our results therefore failed to support the diet specificity hypothesis but were consistent with the prey availability hypothesis.
We highlight that although many other studies are superficially consistent with the diet specificity hypothesis, our study is not alone in failing to provide support and that the hypothesis does not provide a generic explanation for all relevant results. Diet specificity in predators can be at least partially a response to prey diversity, availability and distribution, and benefits associated with different prey types, so that being a generalist is not necessarily intrinsically disadvantageous.
We suggest that the available evidence is more consistent with variation in prey abundance and availability as a more influential factor explaining spatial and temporal variation in breeding productivity of 'generalist' species such as the Golden Eagle. Under this argument, prey abundance and availability are the main drivers of variation in reproductive output. Diet specificity is a consequence of variation in prey availability, rather than a substantial cause of variation in reproductive success.

Birds Can 'Read' Human Gaze

We all know that people sometimes change their behavior when someone is looking their way. Now, a new study reported online on April 2nd in Current Biology shows that jackdaws—birds related to crows and ravens with eyes that appear similar to human eyes—can do the same.

"Jackdaws seem to recognize the eye's role in visual perception, or at the very least they are extremely sensitive to the way that human eyes are oriented," said Auguste von Bayern, formerly of the University of Cambridge and now at the University of Oxford.


Lees meer: Science Daily

Drop In Daddy Long Legs Is Devastating Bird Populations

Warm summers are dramatically reducing populations of daddy long legs, which in turn is having a severe impact on the bird populations which rely on them for food.

New research by a team of bird experts, including Newcastle University's Dr Mark Whittingham, spells out for the first time how climate change may affect upland bird species like the golden plover – perhaps pushing it towards local extinction by the end of the century.

Lees meer: Science Daily
              Birdwatch

Male Nightingales Explore by Day, Seduce by Night

Those who live near nightingale nests know all too well that the males often sing all night.

Yet the birds aren't considered nocturnal animals, as they feed, socialize, and do most of their singing during daylight hours.

"We were really curious why it was that some nightingales were singing in the middle of the night," said Valentin Amrhein of the University of Basel in Switzerland, lead author of a new study on the birds.

Lees meer: National Geographic News

Climate 'hitting Europe's birds'

Climate change is already having an impact on European bird species, according to British scientists.

Details of the study by an international team of researchers have been published in the journal Plos One.

Some birds are expected to do well as temperatures rise, but these are in the minority, the researchers write.

Lees meer: BBC News

Bizarre bird behavior predicted by game theory

A team of scientists, led by the University of Exeter, has used game theory to explain the bizarre behaviour of a group of ravens. Juvenile birds from a roost in North Wales have been observed adopting the unusual strategy of foraging for food in 'gangs'. New research, published in the journal PLoS One (on Wednesday 25 February 2009), explains how this curious behaviour can be predicted by adapting models more commonly used by economists to analyse financial trends.

This is the first time game theory has been used to successfully predict novel animal behaviour in the real world. The researchers believe this analysis could also shed light on the variation in feeding strategies in different populations in other species.

Lees meer: Biology News Net

Kestrel-Prey Dynamic in a Mediterranean Region: The Effect of Generalist Predation and Climatic Factors

Auteurs: Juan A. Fargallo, Jesús Martínez-Padilla, Javier Viñuela, Guillermo Blanco, Ignasi Torre, Pablo Vergara, Liesbeth De Neve
Bron: PLoS ONE 4(2): e4311. doi:10.1371/journal.pone.0004311
Abstract:

Background

Most hypotheses on population limitation of small mammals and their predators come from studies carried out in northern latitudes, mainly in boreal ecosystems. In such regions, many predators specialize on voles and predator-prey systems are simpler compared to southern ecosystems where predator communities are made up mostly of generalists and predator-prey systems are more complex. Determining food limitation in generalist predators is difficult due to their capacity to switch to alternative prey when the basic prey becomes scarce.

Methodology

We monitored the population density of a generalist raptor, the Eurasian kestrel Falco tinnunculus over 15 years in a mountainous Mediterranean area. In addition, we have recorded over 11 years the inter-annual variation in the abundance of two main prey species of kestrels, the common vole Microtus arvalis and the eyed lizard Lacerta lepida and a third species scarcely represented in kestrel diet, the great white-toothed shrew Crocidura russula. We estimated the per capita growth rate (PCGR) to analyse population dynamics of kestrel and predator species.

Principal Findings

Multimodel inference determined that the PCGR of kestrels was better explained by a model containing the population density of only one prey species (the common vole) than a model using a combination of the densities of the three prey species. The PCGR of voles was explained by kestrel abundance in combination with annual rainfall and mean annual temperature. In the case of shrews, growth rate was also affected by kestrel abundance and temperature. Finally, we did not find any correlation between kestrel and lizard abundances.

Significance

Our study showed for the first time vertebrate predator-prey relationships at southern latitudes and determined that only one prey species has the capacity to modulate population dynamics of generalist predators and reveals the importance of climatic factors in the dynamics of micromammal species and lizards in the Mediterranean region.

Lees meer: PLoS ONE

Tracking the Flight of Birds, With Tiny Backpacks

Birds are famous for airborne speed and endurance. Some have been clocked flying 60 miles per hour or more. Others make annual migrations from Alaska to New Zealand, nonstop.

But for scientists, tracking birds as they perform those feats has been an intractable problem. Now researchers think they have cracked it with a novel device — a tiny bird backpack that contains sophisticated sensors and weighs less than a dime.

The new technology has opened up vast new possibilities for bird researchers. Already, it is yielding surprising findings — for example, that some birds fly even faster than previously thought. But its real importance, biologists say, is the opportunity to unlock mysteries of bird migration that could help preserve species threatened by habitat loss and climate change.


Lees meer: NYTimes

Does Red Fox Vulpes vulpes affect bird species richness and abundance in an agricultural landscape?

Auteur(s): Kujawa, Krzysztof; Łęcki, Rafał
Bron: ACTA ORNITHOLOGICA, Volume 43, Number 2, December 2008 , pp. 167-178(12)
Abstract: The aim of the study (carried out 25 km south of Poznań, western Poland) was to determine the impact of Red Fox on bird abundance on farmland. Bird abundance was studied in the years 1999-2000 and 2005-2007 in three categories of sampling plots: 1) in small woods — with or without active fox dens, 2) along transects — starting from dens and running across arable land, and 3) around points — located at dens and far from them. Thus, variability in bird density was analyzed in relation to the presence/absence of Red Fox (in woods) and to the intensity of Red Fox penetration of crops (approximated by distance from a den).

Two groups of bird species were distinguished with respect to their vulnerability to Red Fox predation pressure: 1) potential fox prey, i.e. species nesting on the ground and in low vegetation; and 2) birds not threatened by foxes, i.e. species nesting in tree holes and in tall vegetation. To investigate the relationships between bird distribution and Red Fox dens in woods, a step-wise multiple regression of bird density and species number on woodland structure was first performed.

The residuals derived from the model were used to evaluate the impact of foxes by analyzing the differences between woods with and without active dens. Neither the species number nor the bird density differed significantly between woods with and without active dens. The differences in bird density observed between years in woods with or without active dens were not significant, either. No relationship between bird density in crop fields and distance from fox dens was found.

The results are contrary to those of earlier studies and show that Red Fox does not affect farmland bird distribution, diversity and abundance, at least in the short term.

Birds Survived Mass Extinction That Wiped Out Dinosaurs Because Of Their Larger Brains

The Cretaceous–Tertiary mass extinction 65 million years ago may have wiped out the dinosaurs, but those that survived – the ancestors of today's birds – may have done so because of their bird brains.

Analysis of computer tomography (CT) scans of fossilised bird skulls shows they had a more developed, larger brain than previously thought.

'Birds today are the direct descendents of the Cretaceous extinction survivors, and they went on to become one of the most successful and diverse groups on the planet,' says Natural History Museum palaeontologist (fossil expert), Dr Stig Walsh.


Lees meer: ScienceDaily

Bird Song Discoveries May Lead To Refinement Of Darwinian Theory

For Williams College biology professor Heather Williams, the songs birds sing are more than a pleasant part of a spring day. They are a window into how communication works in the natural world. A birdsong is more than just an encapsulated package of information, it is "a behavior frozen in time."

One of her projects is to record and map out the songs of Savannah sparrows that spend the warmer months on a small Canadian island, Kent Island, in the Bay of Fundy. With the help of microphones, binoculars, and a well-documented set of individual birds, her research is beginning to create a richer view of how birdsong moves from neighbor to neighbor and generation to generation in the wild. And it could lead to a refined way of looking at how communication fits into evolutionary theory.


Lees meer: ScienceDaily

Emperor penguins face extinction

Emperor penguins, whose long treks across Antarctic ice to mate have been immortalised by Hollywood, are heading towards extinction, scientists say.

Based on predictions of sea ice extent from climate change models, the penguins are likely to see their numbers plummet by 95% by 2100.

That corresponds to a decline to just 600 breeding pairs in the world.


Lees meer: BBC News

Aggression and fitness differences between plumage morphs in the common buzzard (Buteo buteo)

Auteurs: M. Boerner, O. Krüger
Bron: BEHAVIORAL ECOLOGY 2009 20(1):180-185; doi:10.1093/beheco/arn132
Abstract: Genetic plumage polymorphism in birds is increasingly recognized as a potentially important trait influencing birds' life histories. In the common buzzard Buteo buteo, the 3 color morphs vary in lifetime reproductive success (LRS), but the proximate mechanisms leading to these differences are unknown. We first confirmed the stability of the fitness differences found previously, using a greatly extended LRS data set.
To find potential causes for these differences, we experimentally studied variation in aggressive behavior of the morphs, both against an interspecific predator and intraspecific competitors. The morphs showed substantial variation in aggressive behavior.
Light-colored males were most aggressive toward an interspecific predator, followed by intermediate and dark males. In females, this pattern was reversed, resulting in sex-related differences of aggression in 2 morphs. When defending their territory against intraspecific competitors, no absolute difference in aggression was found, but the morphs reacted strongest toward intruders of a morph similar to their own.
This suggests that aggression differs both between and within morphs, leading to a complex pattern on the population level. Coupled with the strong fitness differences, our results suggest that the genetic basis of the polymorphism has far-reaching behavioral consequences.

Lower annual fecundity in long-distance migrants than in less migratory birds of temperate Europe

Auteurs: Bruno Bruderer, Volker Salewski
Bron: JOURNAL OF ORNITHOLOGY, Volume 150, Number 1, pp. 281-286
Abstract: We use widely supported handbook data on annual fecundity (clutch size × annual number of normal broods) to obtain indications related to the relative costs of long-distance migration compared to lower levels of migratoriness. Our examples show that the yearly production of eggs in congeneric passerines of similar size from temperate Europe is lower in long-distance migrants than in their less migratory relatives.
The same tendency shows up in a more heterogeneous sample of non-passerines. In most passerines and in one among five pairs of non-passerines, this is due to longer breeding periods allowing a higher number of clutches in the less migratory species in spite of a tendency towards larger clutches in the passerine long-distance migrants.
If both migratory types have only one clutch (as in one species pair of the passerines and in four non-passerine pairs) the trend towards larger clutches was reversed between the two types.
The higher fecundity of the less migratory species suggests that wintering under harsh conditions may be more expensive than trans-Sahara migration among similar species. In keeping with this result, Ortolan and Rock Buntings (Emberiza hortulana and E. cia) breeding syntopically (and, in the 1980s, still in relatively stable populations) in an inner Alpine valley provide a well-studied example illustrating the high longevity of the migrants compared to the relatively short life span of the residents.

Causes, consequences and mechanisms of breeding dispersal in the colonial lesser kestrel, Falco naumanni

Auteurs: Joaquín Ortego, Pedro J. Cordero, José Miguel Aparicio
Bron: ANIMAL BEHAVIOUR, Volume 76, Issue 6, December 2008, pp. 1989-1996
Abstract: Dispersal is a common phenomenon in animals, with important consequences for individual fitness and the genetics and structure of populations. We studied the causes and consequences of breeding dispersal from an individual perspective using as a model organism the colonial lesser kestrel.
For this purpose, we gathered information on 235 birds that attempted to breed in 2 consecutive years (2004–2006) in any of the 22 colonies monitored in the study area. Eighty-two per cent of kestrels returned to the same breeding colony where they had attempted to breed in the previous year. Probability of dispersal decreased with age and individual reproductive performance in the season previous to dispersal and females dispersed more frequently than males. Dispersers settled in colonies with a higher mean reproductive performance than other available colonies located around their colony of origin. However, the size of the colony selected did not differ between selected and surrounding colonies.
Thus, dispersers selected highly productive rather than large colonies. Own body condition or the quality of the mates obtained (estimated by their pectoral thickness and size) did not change for individuals that dispersed or for philopatric individuals in subsequent seasons.
Although dispersers greatly increased their own breeding performance after dispersal, it did not exceed that of their philopatric counterparts. These results help to explain the coexistence of dispersal and philopatric behaviours within a population and suggest that dispersal may be an adaptive behaviour that increases reproductive performance, particularly for individuals that have suffered a bad breeding experience.

The onset of spring and timing of migration in two arctic nesting goose populations: the pink-footed goose Anser bachyrhynchus and the barnacle goose Branta leucopsis

Auteurs: Tombre, Ingunn M.; Høgda, Kjell A.; Madsen, Jesper; Griffin, Larry R.; Kuijken, Eckhart; Shimmings, Paul; Rees, Eileen; Verscheure, Christine
Bron: JOURNAL OF AVIAN BIOLOGY, Volume 39, Number 6, November 2008, pp. 691-703(13)
Abstract: An earlier onset of spring has been recorded for many parts of Eurasia in recent decades. This has consequences for migratory species, both in changing the conditions encountered by individuals on reaching migratory sites and in affecting cues regulating the timing of migration where decisions to migrate are influenced by local environmental variables. Here we examine the timing of spring migration for two arctic goose populations, the pink-footed goose Anser brachyrhynchus (during 1990-2003) and barnacle goose Branta leucopsis (during 1982-2003), which both breed on Svalbard. The satellite-derived Normalised Difference Vegetation Index (NDVI) was used to express the onset of spring at their wintering and spring staging sites.

Pink-footed geese use several sites during spring migration, ranging from the southernmost wintering areas in Belgium to two spring staging areas in Norway, and distances between sites used along the flyway are relatively short. There was a positive correlation in the onset of spring between neighbouring sites, and the geese migrated earlier in early springs.

Barnacle geese, on the other hand, have a long overseas crossing from their wintering grounds in Britain to spring staging areas in Norway. Although spring advanced in both regions, there was no corresponding correlation in the timing of onset of spring between their wintering and spring staging sites, and little evidence for barnacle geese migrating earlier over the whole study period.

Hence, where geese can use spring conditions at one site as an indicator of the conditions they might encounter at the next, they have responded quickly to the advancement of spring, whereas in a situation where they cannot predict, they have not yet responded, despite the advancement of spring in the spring staging area.