Date: July 7, 2016
Source: University of East Anglia
Female birds 'fly the nest' from
sparsely populated breeding sites leaving behind small groups of lonely males
-- according to new research from the University of East Anglia.
Research published in
the Journal of Animal Ecology shows for the first time the causes of
skewed sex ratios among small and declining bird populations.
The findings reveal how female
birds are thought to be choosing busier breeding locations -- where habitat is
often better, males are more abundant, and the ratio of males to females is
more equal.
Lead researcher Prof Jenny Gill,
from UEA's School of Biological Sciences, said: "Many migratory bird
populations are declining and very small local populations are becoming more
common.
"If females prefer places
where males are more abundant, small populations are likely to decline even
faster.
"However, the unpaired males
will continue singing throughout the breeding season in a bid to find a mate,
and so we may be underestimating declines in these small populations. We wanted
to find out whether this was happening."
The research team used British
Trust for Ornithology (BTO) ringing data to explore the extent, causes and
consequences of varying sex ratios in breeding populations of willow warblers
(Phylloscopus trochilus) across the UK.
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