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New publication on passerine migration

Photo: Aron Hejdström 

Different birds use different strategies during migration. However, at some point most of them are forced to fly out over unsuitable habitats, sometimes where it is not even possible to land. This is the case for migratory passerines leaving southern Sweden during autumn migration. 
In a new study Sissel Sjöberg with colleagues look at factors affecting route choice, and which factors that affects the flight duration for the initial flight (the first 50km) across the Baltic Sea. As expected, winds were of dominating importance, both in route choice and in flight duration. More surprisingly, they observed birds departing on a longer flight across the Baltic to depart in a time frame just after sunset and that the flight duration further were affected by both cloudiness and fuel load.

The photo shows one of the robins equipped with a radio transmitter from the study. The automatic radiotelemetry system in Falsterbo makes it possible to follow it during its stay in the area, and depending on route choice, during its departure across the Baltic Sea. This to get a better understanding of stopover and departure behaviour in migratory passerines, and how they affect the overall migratory success.

The study: "Weather and fuel reserves determine departure and flight decisions in passerines migrating across the Baltic Sea" is published in Animal Behaviour.

New model on flapping flight

Nature has produced many formidable flyers and it is tempting to think that evolution has shaped them to be the ultimate flying machines. During the past half-century simple models for estimating flight performance of aircraft have been adopted to also represent animal flight.

However, in a new study, Marco Klein Heerenbrink, Christoffer Johansson and Anders Hedenström show that the aerodynamic efficiency of flying vertebrates has previously been overestimated by ignoring the effects of flapping wings - results that have implications for our understanding of optimal flight behaviour in animals and the use of flapping wings for propulsion in general.

To the paper: "Power of the wingbeat: modelling the effects of flapping wings in vertebrate flight".