GPS tracks golden eagles emigration after flying the nest
06 Nov 2013
Researchers have reported in the BioMed Central open access journal BMC Ecology about new methods that accurately determine when young birds emigrate from the site where they were born. By fitting GPS transmitters to young golden eagles in Scotland, the group demonstrated that the new methods were able to distinguish between trips outside their home range and when the birds had left for good. The works has implications for understanding bird behaviour and subsequently developing better conservation strategies.
Researchers fitted long-lived GPS satellite transmitters to young golden eagles in Scotland in order to determine when they emigrated from the areas they were born. Young birds moving on to new territories or social groups has a profound effect on population dynamics, but indentifying when this happens is difficult. Through devising new, more accurate, methods the group hope to better understand the timings of when young birds leave, giving insight into the different strategies behind this behaviour.
Previous studies have shown that currently used methods are inconsistent, and that there is a tendency to give the young birds’ date of departure as earlier than it is. This may be due to the fact that young birds tend to venture out of their home range before leaving for good. These excursions allow them to assess possible new sites and new social groups, and to decide what would be most beneficial for them. The new methods reported in this article are shown to be able to distinguish between these trips outside of the home range and when the young birds have moved on to new sites.
The young golden eagles left their home territories over a large variable period of time; the first birds leaving at just 39 days and the last at 250 days. A greater understanding of when young birds move on from the place they were born, as opposed to scouting trips outside their home range, will allow researchers to develop hypotheses about why young birds emigrate. This may also lead to more effective strategies for bird conservation.
Ewan Weston, who led the study, said, “With the current interest in when young birds emigrate from their home ranges, this research is of particular importance; understanding when young birds move on is key to furthering our understanding the strategies behind the behaviour.”
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Notes to Editor
1. When do young birds disperse? Tests from studies of golden eagles in Scotland
Ewan D Weston, D Philip Whitfield, Justin MJ Travis and Xavier Lambin
BMC Ecology (in press)
Please credit all images to Ewan D Weston.
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