In 2014, the Town of Kiawah, in
collaboration with Christopher E. Hill,
PhD from Coastal Carolina University,
initiated a more detailed study of the seaside
sparrow at sites around Kiawah Island and
in Georgetown County. There are two subspecies
of seaside sparrows that winter in the salt marshes
around Kiawah Island: the MacGillivray’s seaside sparrow
(Ammodramus maritimus macgillivraii) and the northern
seaside sparrow. The MacGillivray’s seaside sparrow is a
year-round resident (non-migratory) from North Carolina
to northern Florida while the northern seaside sparrow is
migratory and breeds from Maine to Virginia but spends the
winter in the Southeast. In the 2011, the United States Fish
and Wildlife Service agreed to consider protection of the
MacGillivray’s seaside sparrow under the Endangered Species
Act. Because both subspecies are thought to intersperse freely
in the winter, it is important to know the relative population
size for each subspecies. The two subspecies look nearly
identical; therefore, it is not possible to separate them based
on plumage characteristics alone.
A stable isotope of hydrogen is used to
determine the proportion of each subspecies
wintering in the marshes around Kiawah
Island and in Georgetown County.
Because the isotope signature is
somewhat predictable based on latitude,
the values should provide information
on where the birds are breeding. Most of
the hydrogen in bird feathers comes from
what they eat. Seaside sparrows grow new
feathers in the late summer and early fall on
their breeding grounds, so a feather sample taken
from a bird in the winter will still have the hydrogen
content from the breeding season locked into its feathers.
Stable isotopes can also be used to understand how breeding,
migratory, and wintering season populations are connected.
The first round of the feather samples from the Kiawah
Island and Georgetow