II-1. WATERBIRD UTILIZATION OF EAGLE RIVER FLATS
7
II-1. WATERBIRD UTILIZATION OF
EAGLE RIVER FLATS FROM AERIAL SURVEYS:
APRILOCTOBER, 2000
William D. Eldridge
U.S. Fish and Wildlife Service, Anchorage, AK
INTRODUCTION
spring and summer. Surveys were flown us-
ing a fixed-wing aircraft at an airspeed of 100
Aerial surveys to monitor waterbird use of
120 km/hr and an altitude of 7075 m. Total
Eagle River Flats (ERF) during the spring,
coverage of ERF was obtained by overlapping
summer, and fall of 2000 were conducted by
transects. Numbers of waterbirds were
the U.S. Fish and Wildlife Service as part of
counted or estimated and recorded by spe-
the ongoing waterbird mortality and moni-
cies or species group with a cassette tape re-
toring studies of ERF sponsored by the U.S.
corder. Waterfowl numbers were classified by
Army at Ft. Richardson, Anchorage, Alaska.
locations on ERF, using standardized study
The purpose and history of these investiga-
areas (Fig. II-1-1). When possible, birds were
tions have been presented elsewhere (Racine
also recorded by individual ponds within
and Cate 1996).
each study area, using a standardized pond
numbering system. Areas of permanent and
intermittent study ponds were obtained from
STUDY AREA
digitized maps provided by CRREL and used
to convert bird numbers to densities within
Eagle River Flats is a salt marsh complex
the study areas.
comprising 870 ha located on the south side
of Knik Arm, approximately 10 km east of An-
chorage (Fig. II-1-1). A detailed description of
RESULTS AND DISCUSSION
this area is presented in Racine and Cate
(1996).
Moisture conditions
ERF experienced an earlier breakup in 2000
than in 1999, which was a late year. ERF was
METHODS
approximately 85% snow covered by 21 April
2000. By 27 April there was 40% snow cover,
Aerial surveys of ERF were flown from
but most ponds were frozen because of cold
April through October 2000. Surveys were
nights. By 3 May ERF was approximately 10%
conducted more frequently in fall than in
snow covered, and ponds were 30% frozen.
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