Date: May 4, 2016
Source: Central Ornithology
Publication Office
Coastal wading birds shape their
lives around the tides, and new research in The Auk: Ornithological
Advances shows that different species respond differently to shifting
patterns of high and low water according to their size and daily schedules,
even following prey cycles tied to the phases of the moon.
Many birds rely on the shallow
water of the intertidal zone for foraging, but this habitat appears and
disappears as the tide ebbs and flows, with patterns that go through monthly
cycles of strong "spring" and weak "neap" tides. Leonardo
Calle of Montana State University (formerly Florida Atlantic University) and
his colleagues wanted to assess how wading birds respond to these changes,
because different species face different constraints--longer-legged birds can
forage in deeper water than those with shorter legs, and birds that are only
active during the day have different needs than those that will forage day or
night.
Changes in the daily schedules of
tidal flooding affected smaller, daylight-dependent Little Blue Herons more than
Great White Herons, which have longer legs and forage at night when necessary.
The abundance of foraging wading birds was also tied to the phases of the moon,
but this turned out not to be driven directly by changes in the availability of
shallow-water habitat. Instead, the researchers speculate that the birds were
responding to movements of their aquatic prey timed to the spring-neap tide
cycle, a hypothesis that could be confirmed through a study jointly tracking
predator and prey abundance.
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