Date: September 12, 2018
Source: American Ornithological Society Publications
Office
Fledging behavior -- when and why
baby birds leave the nest -- is something scientists know very little about.
Rarely is someone watching a nest at just the right moment to see fledging
happen. To get around this, the researchers behind a new study from The
Auk: Ornithological Advancesdeployed miniature video cameras to monitor over
200 grassland bird nests in Alberta, North Dakota, Minnesota, and Wisconsin,
and they found that fledglings' decision-making process is more complex than
anyone guessed.
Christine Ribic from the U.S.
Geological Survey and her colleagues tested two competing hypotheses about
fledglings' decision making. Birds might leave the nest early in the day to
maximize the amount of time they have to find a safe place to hide from
predators before nightfall. Alternatively, once their siblings start to leave,
the remaining birds might decide to stay in the nest longer to take advantage
of reduced competition for the food their parents provide, resulting in
spread-out fledging times. Video data analyzed by Ribic and her colleagues
showed that the more siblings in a nest, the longer it took for all of them to
fledge, consistent with the idea that some young may stay behind to take
advantage of reduced competition after the first nestlings leave. Ribic and her
co-authors discovered that 20% of nests took more than one day to completely
finish fledging. Fledging behavior also varied between species and over the
course of the breeding season, for reasons that remain unclear.
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