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Photo
by: Christine Kelly  |
Among
shorebirds, 14 species show declining population trends. Three are
listed as Threatened or Endangered under the Endangered
Species Act, and receive Federal protection. Why are they declining
in number? That is what scientists are trying to determine. The
answer may not be the same for every species of shorebird. The puzzle
is particularly tricky for migratory species, such as shorebirds,
since scientists must determine where the losses are occurring during
the specie's life cycle. |
| Are birds dying on
migration or on the wintering grounds? Or is exceptionally low chick
survival responsible for population declines? Most researchers agree
that mortality is highest during the winter. This presents a unique
problem for conservation biologists, since much of the over-wintering
grounds are situated outside of the United States. Fortunately, concern
for endangered and threatened shorebirds is not limited to the U.S.
Partnerships have formed across international boundaries through such
efforts as the Western Hemispheric Shorebird Reserve Network and the
Western Atlantic Shorebird Association to monitor shorebird populations
and preserve shorebird "hotspots". However, a lot of questions
remain to be answered by future scientific research. |
How exactly do scientist study shorebirds? Ideally, research is conducted
at a site for several years in order to detect population trends,
such as declines, over time. At National Wildlife Refuges, shorebird
communities are regularly surveyed each spring and fall. Scientists
conduct surveys or censuses to determine the number of individuals
of each species at a site. This is a measure of shorebird "abundance".
They also count the number of species. This is a measure of "species
richness". Both parameters are important indicators of both the
health of each species' population and of the site. Scientists use
the data to estimate population sizes and migration chronology (the
schedule of migration). |
Many biologists conduct banding studies,
using leg bands to keep track of individual birds. Birds are fitted
with a light weight aluminum U.S. Fish and Wildlife Service leg band
that is engraved with a unique ID number. Some biologists put colored
plastic leg bands on birds so that they can identify the individual
from afar, using spotting scopes. Information on banded birds is used
to make more accurate estimates of population size of a species and
also to determine how long migrants remain on a stopover site and
when the birds depart from a stopover site. This information is a
critical component of management plans. Information on banded birds
is used to make more accurate estimates of population size of a species
and also to determine how long migrants remain on a stopover site
when the birds depart from a stopover site. This information is a
critical component of management plans.
Information on banded birds is used to make more accurate estimates
of population size of a species and also to determine how long migrants
remain on a stopover site and when the birds depart from a stopover
site. This information is a critical component of management plans.
Habitat use is often studied so that land managers at particular sites
will know which areas are preferred by shorebirds so that they can
designate those sites as shorebird habitat. The quality of the habitat
is often studied to determine how it can be improved. A site may require
more frequent flooding from estuary waters in order to foster colonization
of invertebrates to form a richer prey base. |
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Volunteer to count shorebirds at
a National Wildlife Refuge near you. Survey techniques are modeled
after International Shorebird Survey census protocol. Surveys are
conducted every 10 days throughout autumn and spring migration periods
are scheduled around the tide cycle at coastal sites.
Learn how to survey shorebirds
according to International
Shorebird Survey protocol.
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But How Do You
Count So Many Birds At Once?
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* use a tally meter and a good spotting
scope
* count just one or two species at a time
* estimate the size of large flocks by counting a portion of the flock
and then extrapolating for the remaining portion of the flock
* use landmarks to avoid duplicating counts
* bring a friend so that one person can count while the other records
data
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Manomet Center
for Conservation Sciences
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