“There are more and more reports of
osprey overwintering in the Bay,” Dr.
Watts said. “That may be a function of
a warmer climate, and their continued access to fish, which is the main
issue for why they leave.”
Osprey eat a lot of menhaden—small, oily,
bony fish that normally migrate out of the
Bay in the winter to the Carolinas. But with
milder winters, increasing numbers of menhaden also appear to be remaining in the
southern Bay, or at its mouth, off Cape
Henry, Virginia, Dr. Watts said.
With warmer waters, fish might also be
remaining higher in the water column during the winter, which could encourage fish-eating birds to stick around instead of
“As fish go,” Dr. Watts said, “osprey go.”
If this is true, and the apparent trend continues, osprey would not be the first
species of bird to adapt their migrations to
a warming globe.
Several species of song birds, including
warblers and vireos, that normally fly
south in the winter are instead loitering
around the Chesapeake region in the cold
months, Dr. Watts said. In addition, some
waterfowl, such as mergansers and diving
ducks, that summer in Canada and normally fly down to the Chesapeake for the
winter are arriving in diminished numbers,
likely because the northern lakes they live
on are no longer freezing as often.
“Some of these species are shifting their
range as the climate allows them to do that,”
As fish go,
osprey go.” “—DR. BRYAN WATTS
Dr. Watts said. “The evi-
dence is fairly clear that cli-
mate change is happening,
and has been going on for
some time. One doesn’t have to
rely on a bunch of statistics to
know this. We can feel it going on
around us every day.”
Other researchers said Dr. Watts’ observa-
tions about the timing of osprey migrations
match what they’ve seen.
Glenn Therres, a biologist and an associate
director at the Maryland Department of
Natural Resources, said that while osprey
do not appear to be overwintering yet in
Maryland’s portion of the Chesapeake Bay,
he has noticed osprey migrating south later
than normal in the fall.
“There are some late birds leaving the
Chesapeake Bay in November, as opposed
to September,” Therres said. “And we have
noticed a few early returning (osprey)
migrants in the spring.”
Normally, osprey return to Maryland in
mid-March, Therres said. But now some are
showing up about two weeks earlier.
Dr. Alan Poole, Editor of the Birds of North
America project at the Cornell Lab of
Ornithology, said that Dr. Watts is
“absolutely right” to link the change in
osprey migrations to warmer winters and
earlier springs. Dr. Poole said he’s also
noticed osprey returning to Massachusetts
earlier in the spring than usual.
But Dr. Poole said the shift raises a perplex-
ing question: If osprey are returning to
America’s East Coast earlier in the spring,
how do they know—when they are on a
different continent—that they should fly
back earlier because the weather is warmer?
“If you are sitting on the equator, and it’s
100 degrees, you are not going to know if
it’s warmer in Massachusetts this year than
it was last year, are you?” Dr. Poole asked.
The answer might be, Dr. Poole said, that
osprey adjust to weather conditions as they
fly, and move along their traditional migratory routes faster when the weather is warmer.
If that is the case, the change is only the
most recent example of osprey proving
The Chesapeake Bay has been called the
“osprey garden” because it has the most
concentrated populations of the birds in
the world. But osprey are a global species
that have adapted to an extraordinarily
wide range of habitats. Osprey nest on
lakes in Siberia, on the shores of the Red
Sea, in the Boreal forests of Canada, as well
as the salt marshes of the Delmarva
The banning of the pesticide DDT by the
U.S. Environmental Protection Agency in
1972 allowed osprey populations to
rebound, according to Dr. Watts and others. After that, residents and government
agencies around the Chesapeake promoted
osprey breeding by building nesting platforms, and by encouraging osprey to build
nests on channel markers.
Osprey readily adopted these new homes,
Dr. Watts said, because they offered more
protection for their young from predators,
such as raccoons. Historically, about 90
percent of osprey nests were built in trees
along shore. But today, that is reversed,
with 90 percent of nests atop manmade
landmarks, Dr. Watts said.
Whether or not osprey will feel so much at
home atop their Chesapeake channel markers that they will start celebrating Christmas
there…that may be up to the climate.
Tom Pelton is Senior Writer and
Investigative Reporter for the
Chesapeake Bay Foundation.
Read his blog, Bay Daily, at