How an Airplane-Sized Bird Replaced Its Feathers

An extinct bird the size of a Cessna airplane and weighing as much as an average human was one of the largest birds to have ever flown the friendly skies.

Scientists have wondered how the bird, called Argentavis magnificens, could balloon to such heft (more than 150 pounds, or 70 kg) and still replace its feathers during a molt. Now, new research reveals the bird, which lived 6 million years ago in the Miocene epoch, likely molted all of its feathers at once during a long fast.

The finding derives from a larger study that figures out a strange limiting factor to maximum body size in birds — the amount of time it takes to replace flight feathers.

Lees meer: LiveScience

Bird Migrations Set To Increase: Added Distance Is 'Considerable Threat' To Some Species

Bird migrations are likely to get longer according to the first ever study of the potential impacts of climate change on the breeding and winter ranges of migrant birds. The length of some migrations could increase by as much as 400 km. "The predicted future temperature changes and the associated changes in habitat could have serious consequences for many species", said lead-author Nathalie Doswald of Durham University (UK).

Lees meer: Science Daily

What decision rules might pink-footed geese use to depart on migration? An individual-based model

Auteurs: Olivier Duriez, Silke Bauer, Anne Destin, Jesper Madsen, Bart A. Nolet, Richard A. Stillman, Marcel Klaassen
Bron: BEHAVIORAL ECOLOGY, Volume 20, Number 3
Abstract: Decisions taken during migration can have a large effect on the fitness of birds. Migration must be accurately timed with food availability to allow efficient fueling but is also constrained by the optimal arrival date at the breeding site. The decision of when to leave a site can be driven by energetics (sufficient body stores to fuel flight), time-related cues (internal clock under photoperiodic control), or external cues (temperature, food resources). An individual based model (IBM) that allows a mechanistic description of a range of departure decision rules was applied to the spring migration of pink-footed geese (Anser brachyrhynchus) from wintering grounds in Denmark to breeding grounds on Svalbard via 2 Norwegian staging sites. By comparing predicted with observed departure dates, we tested 7 decision rules. The most accurate predictions were obtained from a decision rule based on a combination of cues including the amount of body stores, date, and plant phenology. Decision rules changed over the course of migration with the external cue decreasing in importance and the time-related cue increasing in importance for sites closer to breeding grounds. These results are in accordance with descriptions of goose migration, following the "green-wave": Geese track the onset of plant growth as it moves northward in spring, with an uncoupling toward the end of the migration if time is running out. We demonstrate the potential of IBMs to study the possible mechanisms underlying stopover ecology in migratory birds and to serve as tools to predict consequences of environmental change.

Reproduction of the common buzzard at its northern range margin under climatic change

Auteurs: Aleksi Lehikoinen, Patrik Byholm, Esa Ranta, Pertti Saurola, Jari Valkama, Erkki Korpimäki, Hannu Pietiäinen and Heikki Henttonen
Bron: OIKOS, Volume 118 Issue 6, Pages 829 - 836
Abstract: A changing climate induces shifts in the location of biomes. Tracing such a shift may pose problems for life history traits adapted to the prior conditions, so that, e.g. the timing of reproduction and the time with sufficient resources for rearing hatchlings do not match. We show that the timing of breeding of Finnish common buzzards Buteo buteo, has advanced with over ten days as a response to the warming of early spring, during 1979–2004. During the same period the isoclines of the onset of breeding have moved about 200 km to the north-east. However, the reproductive performance of the common buzzard has not increased as a response to these changes. Despite increasing temperatures during early spring, the temperatures of early summer have remained the same since the 1970s. Combined, the early onset of breeding and the unchanged temperatures of early summer have lead to decreased post-hatching temperatures. Under these circumstances, common buzzard offspring now face a higher risk to hatch into less favourable weather conditions than three decades ago. Furthermore, summer precipitation, harmful for nestlings, has been predicted to increase in the future, thus possibly further worsening the circumstances for breeding common buzzards. Our results demonstrate that even if common buzzards in Finland breed at the northern limit of the species' distribution, and could therefore be expected to gain advantage from a warming climate, the opposite is the case.