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