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