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.