 |
Purple Sandpipers in Coastal Maine
 |
| Researchers from Acadia National Park and other organizations launched a three-year study to learn more about the purple sandpiper (Calidris maritima) in Maine |
During blustery Maine winters, people
- bundled tightly against
the cold - appear only briefly along
the coast. Not so for the sturdy purple sandpiper
(Calidris maritima), which gathers in
flocks along wave-exposed rocky shores to
feed on mussels, amphipods, and other inter-tidal
invertebrates. These stocky, grayish-brown
birds winter along the northeast
Atlantic coast from Newfoundland to Virginia,
the most northerly wintering distribution of
any shorebird. Because little is known about
their ecology and distribution in Maine, biologists
Glen Mittelhauser of the Maine Natural
History Observatory, Lindsay Tudor of the
Maine Department of Inland Fisheries and
Wildlife, and Bruce Connery of Acadia
National Park launched an initial three-year
study in 2001.
The study was designed to assess seasonal
movements and site fidelity, determine
abundance and distribution, and estimate
sex and breeding origin of wintering purple
sandpipers from the Schoodic Peninsula to
western Penobscot Bay. Researchers used a
variety of methods, including analysis of historic
records, boat and shore-based surveys,
capturing and banding, standard body measurements,
dissection, DNA testing, and computer
modeling.
Purple sandpipers were present in the study
area from mid-October to mid-May. The birds
gathered in flocks averaging more than 70
birds. The largest observed flock contained
approximately 900 birds. Fourteen locations
had flocks of more than 250 birds. The Isle
au Haut area included the greatest number of
islands with more than 250 birds, as well as
the greatest number of birds per kilometer of
shoreline surveyed (16.6 birds/km). Using
data from boat and shore-based surveys,
researchers estimated the minimum winter
population from Schoodic to western
Penobscot Bay to be 7,1507,650 birds.
 |
| A U.S. Fish and Wildlife Service researcher takes measurements on a captured bird |
Male and female purple sandpipers differ
in body size. Because females are larger in all
morphological measurements (e.g., weight or
first secondary feather length), researchers
were able to use body measurements to predict
the sex of 89 males and 40 females.
Morphological measurements have been
used in past studies to propose the recognition
of three subspecies of purple sandpiper
(C.maritima): C.m. belcheri, which breeds in
Canada¹s eastern Hudson Bay; C.m. maritima,
which breeds in northern Canada, Greenland,
and northern Europe; and C.m. littoralis,
which breeds in Iceland. Researchers have
suggested, based on body measurements and
recovery of wintering birds banded in New
Brunswick, that at least some of the birds
wintering in eastern North America are part
of the Hudson Bay population (C.m. belcheri).
Although some wintering birds in the study
area were found to be part of the Hudson Bay
population, the majority of birds (80% of
both males and females) were classified as
C.m. maritima, breeding in northern Canada
or northern Europe. The remaining 20% of
males were classified as C.m. belcheri. The
remaining 20% of females were divided
between C.m. belcheri (10%) and C.m. littoralis
(10%).
This study revealed insights that can be
used to help conserve and manage this at-risk
species. Purple sandpipers are particularly vulnerable
along the northeast Atlantic coast. The
Hudson Bay and northern Canada/northern
Europe populations were classified as "Species
of High Concern" in the 2001 U.S. Shorebird
Conservation Plan because of their small population
size and potential threats to the wintering
population at key wintering sites.
Preliminary results of a Maine Department
of Inland Fisheries and Wildlife hazardous
spill analysis demonstrated that purple sandpiper
habitats in Maine are located in areas
with a high vulnerability to oil or other hazardous
material spills. Because of similar
threats in the rest of their wintering range
along the northeast Atlantic coast, the North
Atlantic Regional Shorebird Plan has made it
a priority to identify and protect purple sandpiper
winter habitats along the east coast.
The purple sandpiper distribution outlined
in this study has been used to determine key
areas essential to the survival of the wintering
population, which will help guide the
species¹ conservation in Maine. The inclusion
of key areas in the Maine Oil Plan helps the U.S. Coast Guard determine
where to focus response if an oil spill occurs
along the coast. An analysis of the land ownership
of these key areas has resulted in a listing
of top priorities for purchase or establishment
of conservation easements by the U.S.
Fish and Wildlife Service, National Park
Service, Maine Coast Heritage Trust, and other
environmental agencies and organizations.
This study provides a first step toward
understanding the ecology and winter
requirements of purple sandpipers in Maine,
but questions remain. The breeding origin
of wintering birds needs to be confirmed.
Contrary to previous assumptions, this initial
investigation concluded that only a small percentage
of birds wintering in Maine were part
of the Hudson Bay population. Additional
assessments are necessary to determine
whether subspecies percentages are consistent,
cyclic, or irregular. The research team
also has questions about the fidelity of birds
to specific sites, and whether fidelity is influenced
by age, sex, or flock size. In addition,
researchers must confirm that morphological
measurements can be used to identify all three
subspecies and to serve as an adequate predictor
of sex. Upcoming studies should provide
the answers to these questions, allowing
wildlife managers to continue working
toward the conservation of purple sandpipers
in Maine and elsewhere along the northeast
Atlantic coast.
 |
| During winter, purple sandpipers gather in flocks along wave-lashed rocky shores along the northeast Atlantic coast |
Ginny Reams is the writer-editor at Acadia
National Park.
|
|
 |
|
|
