26/06/2018
New research has highlighted how
biting insects can directly affect the nesting success of Great
Northern Divers.
When sitting on a nest to
incubate eggs, a bird is physically stuck and at its most vulnerable to attacks
of any kind, so coping with stress and other significant costs is
important. For Great Northern Divers, black flies are a common blood-feeding pest
and can cause nest abandonment and decreased fledging rates. This has impacts
on not only individual pair success, but on population dynamics as well.
The new study
has presented some of the best data to date to support hypotheses
about the effects that black flies have on diver nesting behaviour and success.
Chapman University’s Walter Piper and his colleagues monitored Great Northern
Diver nests for 25 years in northern Wisconsin, USA. They marked individuals to
track each bird’s behaviour, nesting success and interaction with black
flies. More than 2,050 nests were included in the study to assess the impacts
of black flies on divers at population level.
If the black fly concentration
around an individual bird was high or it was a particularly intense fly
outbreak year, diver incubation time decreased and nest abandonment increased.
It was discovered that nest abandonment could be predicted using lake size,
female age and the amount of wind. The team found that the smaller the
lake, the older the female and the greater the distance across water that
wind has to travel to reach the nest, the more likely it is that the nest will
be abandoned.
Read on
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