Under my wing: lesser kestrels and jackdaws derive reciprocal benefits in mixed-species colonies

Auteur(s): Daniela Campobello, Maurizio Sara, James F. Hare
Bron: BEHAVIORAL ECOLOGY, doi: 10.1093/beheco/arr207
Abstract: In mixed-species assemblages, antipredator benefits for a timid species nesting close to a more pugnacious one are often reported. Advantages for the protected species are usually manifested in terms of higher reproductive success than conspecifics nesting remote to the protector species. Whether the protector species also accrues any benefit remains untested, and the species-specific behavioral traits underlying enhanced reproductive output in mixed-species associations remain poorly documented. We studied associations between lesser kestrels (Falco naumanni) and jackdaws (Corvus monedula) nesting in rural buildings in the Gela Plain (Italy). We tested for interspecific interactions of jackdaws and lesser kestrels by comparing single- and mixed-species colonies in terms of: 1) vigilance, nest attendance, and intra- and interspecific interference and 2) defensive responses shown by each species when confronted with potential predators or competitors. In both species, nesting in mixed associations was accompanied by decreased vigilance. Diminished vigilance, however, was associated with decreased defensive effort for lesser kestrels, whereas jackdaws increased alarm calling, but only in small colonies. Our results reveal a reciprocal influence on behavior of lesser kestrels and jackdaws nesting within the same colony, whereby both species experience decreased energetic expenditures associated with vigilance, but only lesser kestrels appear to benefit via reduced nest defense effort. We discuss our results in light of the possible asymmetrical information transfer triggered by a common set of nest predators that favors the exchange of interspecific information regarding predator detection and defense.

Lees ook: BBC Nature - 'Truce' benefits bird neighbours

Adulterous Male Birds Don't Put Eggs in One Basket

Males that stray from the nest for adulterous adventures may leave an opening for their mates to cheat, new research on great tit birds suggests.

While these absentee males end up with more adopted chicks from the female mate's flings, they also leave their own offspring in other nests. On average, the "bold" males have the same number of chicks as males who stay home.

Lees meer: LiveScience

Monogamy Helps Geese Reduce Stress

With monogamy so uncommon in the animal world, the idea of lifetime fidelity can seem a little strange, at least to evolutionary biologists.

But in greylag geese, which can live for 20 years and share those years with just one mate, biologists have found a benefit: stress reduction. During fights, males with mates have lower heart rates than their single brethren. If their partners are nearby, they’re even more relaxed.

Lees meer: Wired Science

Delayed autumn migration in northern European waterfowl

Auteurs: Aleksi Lehikoinen, Kim Jaatinen
Bron: JOURNAL OF ORNITHOLOGY, DOI: 10.1007/s10336-011-0777-z
Abstract: Climate change is causing phenological shifts in the environment. Among birds, increasing temperatures have been shown to advance the spring migration and breeding, which in turn affect individual reproductive success. The autumn migration phenology has, however, been largely overlooked. Here, we study long-term changes in the timing of autumn migration in 15 northern European waterfowl species during 1979–2009. We hypothesised that waterfowl should delay their migration since they winter north of the Sahara desert. Our results show that 6 (Greylag Goose Anser anser, Eurasian Wigeon Anas penelope, Eurasian Teal Anas crecca, Tufted Duck Aythya fuligula, Velvet Scoter Melanitta fusca, and Common Goldeneye Bucephala clangula) of the 15 studied species have delayed at least one of the three phases of migration examined. The most marked delay in median migration dates was by more than a month over the past 31 years. Only the Bean Goose Anser fabalis exhibited an advanced beginning of its migration. We also analyse the timing of the entire waterfowl migration and show that the median and end of the migration have been significantly delayed. The results support our predictions and highlight how rapid phenological responses to climate change may be. Such delayed departures may be the cause for recently observed northward shifts of wintering ducks. Our results suggest that waterfowl to be a good indicator group for climate change. Changing migration times can also have population-level consequences due to differential hunting and natural predation pressures over the waterfowl flyway.

Individually tracked geese follow peaks of temperature acceleration during spring migration

Auteurs: Rien E. van WIjk, Andrea Kölzsch, Helmut Kruckenberg, Bartwolt S. Ebbinge, Gerhard J.D.M. Müskens, Bart A. Nolet
Bron: OIKOS, Article first published online: 8 NOV 2011, DOI: 10.1111/j.1600-0706.2011.20083.x
Abstract: Many migratory herbivores seem to follow the flush of plant growth during migration in order to acquire the most nutrient-rich plants. This has also been hypothesized for arctic-breeding geese, but so far no test of this so-called green wave hypothesis has been performed at the individual level. During four years, a total of 30 greater white-fronted geese Anser albifrons albifrons was tracked using GPS transmitters, of which 13 yielded complete spring migration tracks. From those birds we defined stopover sites and related the date of arrival at each of these stopovers to temperature sum (growing degree days, GDD), snow cover, accumulated photoperiod and latitude. We found that geese arrived at spring stopovers close to the peak in GDD jerk; the ‘jerk’ is the third derivative, or the rate of change in acceleration, and GDD jerk maxima therefore represent the highest acceleration of daily temperature per site. Day of snow melt also correlated well with the observed arrival of the geese. Factors not closely related to onset of spring, i.e. accumulated photoperiod and latitude, yielded poorer fits. A comparison with published data revealed that the GDD jerk occurs 1–2 weeks earlier than the onset of spring derived from NDVI, and probably represents the very start of spring growth. Our data therefore suggest that white-fronted geese track the front of the green wave in spring.

Adaptive significance of permanent female mimicry in a bird of prey

Auteurs: Audrey Sternalski, François Mougeot, Vincent Bretagnolle
Bron: BIOLOGY LETTERS, Published online before print November 9, 2011, doi: 10.1098/rsbl.2011.0914
Abstract: Permanent female mimicry, in which adult males express a female phenotype, is known only from two bird species. A likely benefit of female mimicry is reduced intrasexual competition, allowing female-like males to access breeding resources while avoiding costly fights with typical territorial males. We tested this hypothesis in a population of marsh harriers Circus aeruginosus in which approximately 40 per cent of sexually mature males exhibit a permanent, i.e. lifelong, female plumage phenotype. Using simulated territorial intrusions, we measured aggressive responses of breeding males towards conspecific decoys of females, female-like males and typical males. We show that aggressive responses varied with both the type of decoys and the type of defending male. Typical males were aggressive towards typical male decoys more than they were towards female-like male decoys; female-like male decoys were attacked at a rate similar to that of female decoys. By contrast, female-like males tolerated male decoys (both typical and female-like) and directed their aggression towards female decoys. Thus, agonistic responses were intrasexual in typical males but intersexual in female-like males, indicating that the latter not only look like females but also behave like them when defending breeding resources. When intrasexual aggression is high, permanent female mimicry is arguably adaptive and could be seen as a permanent ‘non-aggression pact’ with other males.

Lees ook: Why some birds of prey become transvestites
             Cross-dressing raptors avoid violence

The paradox of spoonbill migration: most birds travel to where survival rates are lowest

Authors: Tamar Lok, Otto Overdijk, Joost M. Tinbergen, Theunis Piersma
Bron: ANIMAL BEHAVIOUR, Volume 82, Issue 4, October 2011, Pages 837-844
Abstract: Migrant birds face a choice where to spend the winter. Presumably there is a trade-off between migration distance (costs) and the quality of the wintering site (benefits). Wintering site fidelity is often high and increases with age. Hypotheses to explain such a pattern assume that wintering site choice maximizes fitness. We compared wintering site choice and age-dependent site fidelity in Eurasian spoonbills, Platalea leucorodia leucorodia, for the period 1992–2010. During their first southward migration, most spoonbills migrated to the southernmost wintering region (Mauritania and Senegal). Other birds were likely to move there from their first to their second winter, whereas hardly any birds moved to a more northerly wintering area. For the rest of their life, spoonbills remained highly site faithful. This resulted in most birds wintering in Mauritania and Senegal with smaller numbers in France and Iberia. We judged suitability of sites on the basis of annual survival probabilities in these three wintering areas. Surprisingly, survival was lowest in Mauritania and Senegal. None of the existing fitness maximization hypotheses explain this pattern and we discuss potential alternatives. Wintering site choice could still be optimal for individual birds if birds wintering in Mauritania and Senegal are competitively inferior to the European winterers or more susceptible to severe winter weather. Alternatively, wintering site choice of spoonbills is suboptimal and, assuming that spoonbills can assess differences in suitability, limited flexibility may prevent them from switching to more suitable sites.

Smells May Help Birds Find Their Homes, Avoid Inbreeding; Research May Bring Help to Endangered Species

Birds may have a more highly developed sense of smell than researchers previously thought, contend scholars who have found that penguins may use smell to determine if they are related to a potential mate.

The research by the University of Chicago and the Chicago Zoological Society, which manages Brookfield Zoo, shows how related birds are able to recognize each other. The study, published Sept. 21 in the journal PLoS ONE, could help conservationists design programs to help preserve endangered species.

Lees meer: ScienceDaily

Feathered Friends Help Wild Birds Innovate

Larger groups of great and blue tits are better at solving problems than smaller ones, Oxford University scientists have found. The researchers believe that this is probably because the larger the group, the more chance there is of it including a 'bright' or 'experienced' bird that can solve a particular new problem: in this case operating lever-pulling devices to receive a food reward.

The study took place on wild populations of great tits (Parus major) and blue tits (Cyanistes caeruleus), which naturally flock together, in Oxford's Wytham Woods. A report of the research appears this week in Proceedings of the National Academy of Sciences.

Lees meer: ScienceDaily

It’s All in the Head: Songbirds With Bigger Brains Have Benefited from the End of Communism

According to a new study published in Biological Conservation the abundance of songbirds with relatively large brains in Eastern Germany and the Czech Republic has increased since 1989 / 1990. Researchers from German Biodiversity and Climate Research Centre (BiK-F) and Czech Charles University in collaboration with "Dachverband Deutscher Avifaunisten" (Federation of German Avifaunists) had compared population trends of bird species in different European regions. The increase in large-brained songbirds is attributed to the better cognitive abilities of the species enabling them better adaption to the socio-economic changes affecting habitats after the end of communism.

Lees meer: ScienceDaily

De vogeltjes op het droge hebben

Migrerende vogels hebben voldoende water nodig om hun uitputtende vluchten te kunnen volbrengen. Maar hoe komt het dat ze niet uitdrogen zonder regelmatig een pitstop te maken? Door tijdens het vliegen spierweefsel af te breken.

Tijdens migratie leggen sommige vogels duizenden kilometers af tussen broedplaats en winteroptrekje, met van tijd tot tijd een stop om ‘bij te tanken’. De energie om voor langere tijd in de lucht te blijven halen ze voornamelijk uit de afbraak van vetzuren uit hun vetopslag. Eiwitten worden ook afgebroken, ook als er nog genoeg vetreserves zijn, waardoor spieren en organen in grootte afnemen tijdens de reis. Dit lijkt niet ideaal, want het kost bij een stop meer tijd om de eiwitvoorraad weer aan te vullen dan de vetvoorraad. Maar daarmee voorkomen de vogels dat ze uitdrogen, schrijven onderzoekers in Science.

Lees meer: Wetenschap 24

More godwits in bird-friendly managed meadowlands

Bird-friendly meadowland management measurably benefits godwits according to researchers at the University of Groningen, based on four years of field work conducted in southwest Friesland. An egg laid in farmland with a higher water table, greater plant variety among the grass and a later mowing date has no less than a 17 times greater chance to lead to a mature godwit the following spring than an egg laid in highly productive, intensively farmed fields, in other words farmland managed in traditional fashion.

Lees meer: ScienceDaily

The quick bird catches the girl

While the early bird might catch the worm, it's the quick bird that lands the ladies, according to new research into the running performance of an Arctic cousin of the grouse.

Scientists studying rock ptarmigan on the Norwegian archipelago of Svalbard discovered a large difference in the running capabilities between the sexes, with the larger males able to run more efficiently and up to 50% faster than females.

Lees meer: ScienceDaily

Low-frequency songs lose their potency in noisy urban conditions

Auteurs: Wouter Halfwerk, Sander Bot, Jasper Buikx, Marco van der Velde, Jan Komdeur, Carel ten Cate, Hans Slabbekoorn
Bron: Proceedings of the National Academy of Sciences of the United States of America, doi 10.1073/pnas.1109091108, August 29 2011
Abstract: Many animal species communicate with their mates through acoustic signals, but this communication seems to become a struggle in urbanized areas because of increasing anthropogenic noise levels. Several bird species have been reported to increase song frequency by which they reduce the masking impact of spectrally overlapping noise. However, it remains unclear whether such behavioral flexibility provides a sufficient solution to noisy urban conditions or whether there are hidden costs. Species may rely on low frequencies to attract and impress females, and the use of high frequencies may, therefore, come at the cost of reduced attractiveness. We studied the potential tradeoff between signal strength and signal detection in a successful urban bird species, the great tit (Parus major). We show that the use of low-frequency songs by males is related to female fertility as well as sexual fidelity. We experimentally show that urban noise conditions impair male–female communication and that signal efficiency depends on song frequency in the presence of noise. Our data reveal a response advantage for high-frequency songs during sexual signaling in noisy conditions, whereas low-frequency songs are likely to be preferred. These data are critical for our understanding of the impact of anthropogenic noise on wild-ranging birds, because they provide evidence for low-frequency songs being linked to reproductive success and to be affected by noise-dependent signal efficiency.

Lees meer: Vrouwelijke koolmees valt voor lage tonen | Kennislink

Puffins 'Scout Out' Best Migration Route

Individual Atlantic puffins 'scout out' their own migration routes rather than relying on genetic 'programming' or learning routes from a parent, a new study suggests.

The evidence comes from research by a team from Oxford University and Microsoft Research Cambridge which used BAS geolocater tags to track the migration movements of 18 birds: with 8 of these birds being tracked for two consecutive years.Individual Atlantic puffins 'scout out' their own migration routes rather than relying on genetic 'programming' or learning routes from a parent, a new study suggests.

Lees meer: ScienceDaily

Individuality in bird migration: routes and timing

Auteur(s): Vardanis, Y (Vardanis, Yannis); Klaassen, RHG (Klaassen, Raymond H. G.); Strandberg, R (Strandberg, Roine); Alerstam, T (Alerstam, Thomas)
Bron: BIOLOGY LETTERS, Volume 7, Issue 4, Pages 502-505, DOI: 10.1098/rsbl.2010.1180
Abstract: The exploration of animal migration has entered a new era with individual-based tracking during multiple years. Here, we investigated repeated migratory journeys of a long-distance migrating bird, the marsh harrier Circus aeruginosus, in order to analyse the variation within and between individuals with respect to routes and timing. We found that there was a stronger individual repeatability in time than in space. Thus, the annual timing of migration varied much less between repeated journeys of the same individual than between different individuals, while there was considerable variation in the routes of the same individual on repeated journeys. The overall contrast in repeatability between time and space was unexpected and may be owing to strong endogenous control of timing, while short-term variation in environmental conditions (weather and habitat) might promote route flexibility. The individual variation in migration routes indicates that the birds navigate mainly by other means than detailed route recapitulation based on landmark recognition.

Arctic melting will affect the migratory strategies of seabirds

A study of kittiwakes (Rissa tridactyla) in the arctic region provides the first data on the migratory patterns of this seabird species and analyses its capacity to respond to environmental changes. The kittiwake is one of the most emblematic marine species of the arctic area, and evidence suggests that rising temperatures at the north pole over the coming decades will have a dramatic impact on populations of this bird.

To understand the responses of arctic species to climate change, an international team led by Thierry Boulinier (Centre for Functional and Evolutionary Ecology, CNRS, France), contributed to by the lecturer Jacob González-Solís, from the UB's Department of Animal Biology and the Institute for Research on Biodiversity (IRBio), has fitted tracking devices to individuals from several kittiwake populations in northern Norway.

Lees meer: ScienceDaily

Scotland’s long-distance dining seabirds

Initial findings of a ground-breaking project that tracks Scotland’s seabirds using technology akin to car ‘sat-navs’, has revealed that seabirds are foraging much further afield than scientists had thought.

The Future of the Atlantic Marine Environment (FAME) project tracks Common Guillemot, Kittiwake and other seabird species in an attempt to identify crucial marine feeding locations. The project followed several birds from the Northern Isles looking for food vast distances from the colony while others stayed closer to home. The islands are together home to some of Scotland’s most important “seabird cities”.

Lees meer: Birdwatch Magazine

Gyrfalcons are 'secret seabirds'

The world's largest falcon, the fast, taloned gyrfalcon, is a secret seabird, scientists have discovered.

Gyrfalcons living in the high Arctic overwinter out at sea, spending long periods living and hunting on pack ice.

It is the first time any falcon species has been found regularly living at sea.

The birds likely rest on the ice and hunt other seabirds such as gulls and guillemots, over what appears to be one of the largest winter ranges yet documented for any raptor.

Lees meer: BBC Nature

What the Duck? Lady Mallards May Get Down With Bright-Billed Drakes to Avoid STDs

When it comes to mallard bills, brighter is better: A bright yellow bill is duck-speak for “I’m healthy,” attracting more female ducks than dingy green ones. After discovering that avian semen has antibacterial properties, scientists then found that the semen of brighter-billed males killed more bacteria than the semen of darker-billed ones. It implies that by seeking out bright-billed males, female ducks are protecting themselves against bacteria-related sexually transmitted diseases.

Lees meer: Discover Magazine

Birds Dumping Eggs on the Neighbors

A huge study of over 69,000 nests around the west coast of Scotland has revealed for the first time the full extent of egg dumping by seabirds. The findings show that cuckoos aren't the only birds to lay eggs in other birds' nests, and may give an insight into how so-called brood parasitism evolved.

While the cuckoo is famous for laying its eggs in other birds' nests, this habit is rare and poorly understood among seabirds.

Lees meer: ScienceDaily

Migration and wintering areas of adult Montagu’s Harriers (Circus pygargus) breeding in Spain

Auteur(s): Ruben Limiñana, Alvaro Soutullo, Vicente Urios and Abilio Reig-Ferrer
Bron: Journal of Ornithology DOI: 10.1007/s10336-011-0698-x
Abstract: Between 2006 and 2008, 14 Montagu’s Harriers (Circus pygargus) were tagged with satellite transmitters at their breeding grounds in NE Spain, recording a total of 18 autumn and 10 spring journeys. In both autumn and spring migrations, harriers migrated between Europe and West Africa along a relatively narrow corridor between the coast of Morocco and Western Sahara and the western border of Algeria. Birds tended to follow a slightly more westerly track during spring migration compared to autumn migration. Harriers started autumn migration in late August–early September, arriving at their wintering grounds in early–mid-September, after travelling between 8 and 25 days, and covering a mean of 187 km a day. Spring migration started in mid-March, with birds arriving at the breeding grounds in mid-April after covering a mean of 114 km a day. On average, spring migration lasted longer, with birds covering longer distances than during autumn migration, and distances travelled in a day tended to be shorter. Significant differences in the routes followed by harriers were observed among seasons and individuals, with the same individuals following different routes in different years. Wintering areas were located in northern Senegal and the southern border of Mauritania with Mali, with some birds breeding in the same colony in Europe separated more than 1,200 km during the wintering season. Birds showed a relatively high fidelity to their wintering areas. Several birds moved from one area to another during the wintering period, which resulted in larger wintering areas, whereas others remained in the same area during the whole wintering season.

Declining rainfall is a major influence for migrating birds

Instinct and the annual increase of daylight hours have long been thought to be the triggers for birds to begin their spring migration. Scientists at the Smithsonian Conservation Biology Institute, however, have found that that may not be the case. Researchers have focused on how warming trends in temperate breeding areas disrupt the sensitive ecology of migratory birds. This new research shows that changes in rainfall on the tropical wintering grounds could be equally disruptive.

The team's findings are published in scientific journal Proceedings of the Royal Society B on March 30.

Lees meer: ScienceDaily

Swifts have duvet days

Common Swifts enter a form of hibernation when the weather turns bad, new research has revealed.

Mark Walker and Prof. Ian Rotherham of Sheffield Hallam University discovered that on cold wet summer days, flying insects become scarce. On such days, nestling Common Swifts were often also extremely cold. Nestlings of most bird species die quickly if their body temperature drops by even a small amount. However, swifts were able to survive even when their body temperature dropped by almost half.

Lees meer: Birdwatch Magazine

Zeevogels verspreiden dodelijk plastic over hele wereld

Jaarlijks vervoeren zeevogels honderden ton plastic van de ene naar de andere kant van de wereld. De vogels verwarren kleine stukjes plastic met voedsel.

De toename van plastic zwerfvuil heeft wereldwijd een massale sterfte van vogels, zeedieren en vissen tot gevolg. Neem de albatrossen op afgelegen atollen in de Stille Oceaan. Die voeden hun kuikens met kleine stukjes plastic die op voedsel lijken. De kuikens sterven van ondervoeding en wanneer hun kadavers vergaan, belanden die stukjes plastic weer in zee. Een funeste versie van recyclage.

Lees meer: ARGUS actueel

Frightened birds grow longer wings

Offspring of predator-stressed mothers grow their wings more quickly than chicks from predator-free females.

It seems that the constant threat of predation could have a more subtle effect on prey animals than first thought.

Female birds that are exposed to predators while they are ovulating produce smaller offspring than unexposed females, researchers have found. The chicks may be smaller, but surprisingly, their wings grow faster and longer than those of chicks from unexposed mothers — an adaptation that might make them better at avoiding predators in flight.

Lees meer: Nature News

Colony- and age-specific seasonal dispersal of Herring Gulls Larus argentatus breeding in The Netherlands

Auteurs: C. J. Camphuysen, Harry J. P. Vercruijsse and Arie L. Spaans
Bron: JOURNAL OF ORNITHOLOGY, DOI: 10.1007/s10336-011-0664-7, online first
Abstract: The Herring Gull population in The Netherlands went through phases of exploitation, protection, persecution and again (partial) protection during the nineteenth and twentieth centuries. The numbers of breeding pairs peaked in the 1980s at approximately 90,000 pairs, at which point a colour-ringing campaign was organised to evaluate dispersal and distribution patterns. Herring Gulls were ringed as chicks, predominately near-fledglings, in 12 colonies in 1986 (1,247 individuals), 13 colonies in 1987 (1,354 individuals) and 14 colonies in 1988 (1,396 individuals). Between 1986 and 2009, of the 3,997 Herring Gull chicks colour-ringed, 3,124 individuals (78.2%) were seen and reported at least once, while 453 (11.3%) were recovered dead. In total, 86,247 ring-readings of living gulls were received and processed, originating from 1,358 locations by 868 observers. One-fifth (20.5%) of all sightings originated from the home-ranges (areas within a radius of 5 km around the ringing place). Only 691 sightings (0.8%) were reported at over 300 km from the natal colony (10.7% at 6–10 km, 8.9% at 11–25 km, 17.7% at 26–50 km, 22.9% at 51–100 km, 14.4% at 101–200 km and 4.1% at 201–300 km). Colony-specific differences in travelling distance, dispersal rate and direction of movements suggest a grouping of colonies in three areas: (1) eastern Wadden Sea islands (Rottumeroog–Vlieland), with significantly higher dispersal rates and movements mostly towards the south-west to south-east; (2) Texel and the four colonies along the mainland coast (Callantsoog–Wassenaar), with shorter mean range and movements mostly to the south; (3) colonies in the Delta area (Europoort–Saeftinghe), with rather short range movements and dispersal in many directions. The maximum distance travelled did not vary much between adults, immatures and juveniles, but the timing of outward and return movements was different for each of these age categories. Adult birds reached their greatest mean distances on average 1 month earlier than immatures, which in turn arrived at this point 1 month earlier than juveniles. These age-specific differences were enhanced in the spring, when birds were moving towards the (natal) colonies, but when adults moved on average closer and 2 months ahead of immatures, which in turn moved earlier and closer to the natal home-range than juveniles. With reference to findings from other studies in other European countries, Herring Gulls breeding in The Netherlands occupies a mid-position between dispersive and sedentary tendencies.

Mystery behind decline in UK’s waders

Population has halved in 25 years
February 2011: No single cause can explain the recent decreases in the UK's wader population, according to a new RSPB study, which instead suggests that different factors associated with varying land use may be influencing changes in certain species.

Lees meer: Wildlife Extra News

Shift in crop preference during the breeding season by Yellow Wagtails Motacilla flava flava on arable farms in The Netherlands

Auteurs: Steven Kragten
Bron: JOURNAL OF ORNITHOLOGY - DOI 10.1007/s10336-011-0655-8 - Online First
Abstract: Dutch farmland bird populations are in steep decline as a result of agricultural intensification. The Yellow Wagtail (Motacilla flava flava) is one of those species, but its decrease has mainly occurred in grasslands, with its population in arable areas remaining more or less stable. In contrast, populations of other typical birds of arable habitats, such as the Skylark (Alauda arvensis) and Grey Partridge (Perdix perdix),are declining strongly in this habitat type. The favorable status of the Yellow Wagtail is probably caused by the crop-mosaic composition of arable farms in The Netherlands, which often includes winter cereals, potatoes, and sugar beet. This study focused on crop preference by the Yellow Wagtail during the breeding season. Early in the breeding season Yellow Wagtails showed a strong preference for winter cereals. However, as the breeding season progressed, their preference gradually shifted to broad-leaved crops, especially potatoes. Measurements of the crop structure as an indication for vegetation height or bare ground, revealed that the Yellow Wagtail strongly preferred crops 20–40 cm high. Higher crops were also used more than expected based on a uniform distribution, but to a lesser extent, and crops <20 cm in heigth were not preferred at all. In terms of ground coverage, Yellow Wagtails preferred crops providing a ground coverage of at least 60%. There was a negative association between Yellow Wagtail numbers and crops providing <20% ground coverage.

Ruddy hell: turnstone flies 27,000 kms – twice!!

Researchers from the Victorian Wader Study Group – a special interest group of Birds Australia [BirdLife Partner] - have just recaptured a Ruddy Turnstone Arenaria interpres which has completed a 27,000 km round trip migration for the second time.

This is the first time a wader has been tracked with a geolocator on its complete migration in successive years.

The bird had a one gram light sensor data logger (geolocator) attached
to its leg. This device recorded where the bird was each morning and
evening. In each year the device was attached to the bird in mid April
on a beach at Flinders, Victoria, in southeast Australia.


Lees meer: BirdLife International

Hormones dictate breeding success in birds

Max Planck and Princeton University researchers can predict the number of offspring a bird will have based on its prolactin and corticosterone levels.

Some animals produce more offspring than others. Hormones like prolactin and corticosterone can exercise a crucial influence on the behaviour of birds in the breeding season and therefore on their reproductive success. Scientists from the Max Planck Institute for Ornithology in Radolfzell and their colleagues at the universities of Princeton and Edinburgh have now demonstrated that hormone levels not only play a key role during the breeding season, but already dictate, long in advance, how many eggs a breeding pair will lay, when they will lay them and how often. An animal's hormonal constitution is thus of major significance for its reproductive success, and is possibly an important driving force of evolution.

Lees meer: ScienceDaily

Raptor Nest Decorations Are a Reliable Threat Against Conspecifics

The discovery of messages in raptors’ nests has raised the possibility that many bird species encode signals into these structures, with seemingly decorative flourishes actually full of meaning.

Among black kites, scraps of white plastic are used to signal territorial dominance. To other kites, the scraps are a warning sign. To humans, they hint at an unappreciated world of animal communication.

“It’s probably very common that other bird species decorate their nests in ways compatible with what we found,” said Fabrizio Sergio, a biologist at the Doñana Biological Station in Spain. “And not only birds, but fish and mammals.”

Lees meer: Wired Science

Biological clock ticks slower for female birds who choose good mates

In birds as in people, female fertility declines with age. But some female birds can slow the ticking of their biological clocks by choosing the right mates, says a new study.

Female birds become progressively less fertile as age takes its toll, said co-author Josh Auld of the National Evolutionary Synthesis Center in Durham, North Carolina. Older females lay fewer eggs, and they lay them later in the season -- at a time when less food is available for their chicks, he explained.

But despite abundant evidence of fading fertility in females, scientists know little about the role played by their mates. "The thought was that males didn't matter," Auld said.

Lees meer: ScienceDaily

Songbird’s Sex Hormone Surges at Sight of Flowers

As summer heats up, the sight of blooming thistles may give male goldfinches a testosterone kick.

Thistle flowers could signal to American goldfinches that the seeds the songbirds prize for baby food and parent food will soon be abundant, proposes Thomas Luloff of the University of Western Ontario in London, Canada. And in lab setups, male goldfinches housed among blooming Canadian thistles underwent physiological changes that indicate the birds got the “breed now” message from the combination of summery heat and thrilling thistles, Luloff reported January 6 at the annual meeting of the Society for Integrative and Comparative Biology.

Lees meer: Wired Science

How seabirds share their habitat

When different species of seabirds share a habitat with limited sources of food, they must differ in their feeding habits. This specialisation is known by biologists as an "ecological niche." Researchers at the Max Planck Institute for Ornithology in Radolfzell have investigated how flexible these ecological niches really are. They discovered that the preying habits of diving seabirds are very different, both in location and timing, within species as well as between different species.

Ecological niches are not inflexible; they are affected by different habitats and the need to avoid competition with neighbours or evade predators, and also lead to different forms of behaviour within a single species.

Lees meer: ScienceDaily