More information about CAnMove and the research activities within the programme can be found at:


fredag 30 april 2010

Storms influence patterns of tropical bird migration

Montane tropical forest in Costa Rica, with a White Ruffed Manakin (inset). Photograph courtesy of Alice Boyle

In an interesting paper published online recently in Proceedings of the Royal Society B (Boyle et al 2010: see link below), Dr. Alice Boyle and co-workers present research into the effect of storms upon migration in tropical birds. Many animals, including birds, bats and insects, migrate up and down elevational gradients, from the lowlands to higher ground in mountainous regions of tropical forest. This is known as altitudinal migration, and the factors that drive animals to migrate in this fashion remain obscure. One idea, proposed forty years ago by Alexander Skutch, is that tropical storms could force tropical birds to migrate downhill. In this paper, Dr. Boyle and her co-workers test this idea, and also suggest a mechanism. They propose that one explanation for these patterns may be that storms reduce the time a bird can spend finding food at higher altitudes more than at lower altitudes, and that this reduction in foraging time may pose a very real risk of starvation.

Dr. Boyle tested these hypotheses with a species of partially migratory tropical bird, the White-ruffed manakin. White-ruffed manakins are small fruit-eating birds that breed in the wet, mountainous forests of Central America. After the breeding season some birds migrate downhill to lower altitudes whilst some remain at higher altitudes. Dr. Boyle found that capture rates at higher elevation decrease during storms and increase at lower altitudes, which suggests that storms do play a role in altitudinal migration in this species. Interestingly, at high altitudes before storms there is a bias towards males, and after storms a bias towards females, which may be linked to differences in body size between sexes (males are around 15% smaller). By collecting blood samples from birds and analyzing physiological measures of body condition, Dr. Boyle also found support for her ‘limited foraging opportunities’ hypothesis: rainfall was associated with plasma coricosterone levels, fat stores, plasma metabolites and haematocrit. These results suggest that weather-related risks for species requiring high food intakes can explain the altitudinal migrations of tropical animals. This is an important advance in our understanding of animal migration in the tropics, which may be important in conservation efforts. Furthermore, this work suggests that climate change may have significant impacts upon migratory birds in the tropics, as global warming is predicted to alter the severity and timing of rainfall events in tropical regions of the world.

/ Ben

Here is the link to the full paper:


torsdag 22 april 2010

New publication: Grand Challenges in Migration Biology

Three members of CAnMove (Melissa Bowlin, Susanne Åkesson, and Anders Hedenström) are among the authors of a review recently published online by the journal Integrative and Comparative Biology. The paper, titled, ‘Grand Challenges in Migration Biology’, advocates the use of integrative research to address the big questions in the field of migration biology. It grew out of a symposium titled, ‘Integrative Migration Biology,’ organized by Melissa Bowlin, Isabelle-Anne Bisson, and Martin Wikelski at the annual Society for Integrative and Comparative Biology meeting in Seattle last January.

In the paper, Bowlin et al. argue that the best way to meet the ‘grand challenges’ of migration biology is to perform multidisciplinary research that includes multiple species and clades as well as the entire annual cycle of organisms. They also stress the importance of a strong theoretical foundation and the need to study migrants both in the laboratory and out in the field. The paper concludes by highlighting the data the authors believe will prove to be vital for conservation efforts.

‘Grand Challenges in Migration Biology’ can be found on the ‘advance access’ section of ICB’s website, here: http://icb.oxfordjournals.org/papbyrecent.dtl .


Photo: Arne Hegemann

torsdag 15 april 2010

PI Lectures on web

During the popular science week given earlier this spring for gymnasium students at the Ecology Building CAnMove PI Åke Lindström lectured on “Dow Jones Index och svensk fågeltaxering” (Dow Jones index and the Swedish breeding bird censusing). PI Dennis Hasselquist also lectured on the theme “Harmoni och kaos I naturen – om lämmercykler och fågelinfluensa (Harmony and chaos in nature – about lemming cycles and bird influensa). Both lectures are very interesting and are available at:


söndag 4 april 2010

Daytime flight of emerging bats

In temperate regions bats survive the winter either by hibernation (the typical bat strategy) or by migration south combined with hibernation in the wintering area. The fuel for hibernation (and migration) is fat, which is consumed at a slow rate throughout the winter. About now (March/April) is the time to wake up for hibernators, when they are running low on fat loads and they have to find food to survive. It is not uncommon to see bats flying around during daytime at the time of emergence from hibernacula. On good Friday (2nd April) the Hedenström-Åkesson family had been bird watching around Voms ängar and Krankesjön, when they drove back a small bat flying back and forth along the road on the Revinge field was spotted at 14:20. They managed to get some photos, from which it is apparent we are dealing with a Pipistrellus species. The most common, and hence most likely, species in Sweden is P. pygmaeus (dvärgfladdermus), but P. pipistrellus (pipistrell) and P. nathusii (trollfladdermus) cannot easily be excluded on the basis of the photos. Why are bats emerging from hibernation sometimes flying in daylight? It could be that they are in such a desperate need for energy that they need to feed in daytime; perhaps diurnal insects are more abundant than nocturnal insects at this time of the year? It could also be that the circadian clock has drifted during the winter sleep, which makes them fly at the “wrong” time?