Bald eagle nesting chronology and implications for surveys

1 Pages·1994·0.39 MB·English

by  P F Schempf

March 1994 Abstracts 65
Bald Eagle Nesting Chronology and Implications Judging from sightings and eggs collected over 75 years
FOR Surveys ago, the current breeding distribution of ferruginous hawks
{Buteo regalis) in Canada includes only the southern 50%
SCHEMPF, P.F. U.S. Fish and Wildlife Service, 3000 Vin-
AK of the former range. In response to this decline, the fer-
tage Park Boulevard, Suite 240, Juneau, 99801 U.S.A.
ruginous hawk was assigned “threatened” status in 1980
Occupancy and reproduction surveys were conducted at A recovery team first met to help enhance this species’
594 bald eagle (Haliaeetus leucocephalus) nests in Prince recovery in 1990. A considerable amount of monitoring,
William Sound, Alaska, during the summer of 1990. Sur- nest management and habitat protection has been devoted
veys began in early April and were repeated at 10 d in- to this species. During the last ten years, ferruginous hawks
tervals throughout the breeding season until young began have remained stable or increased slightly on selected study
to fledge in mid-August. The standard method of con- areas in the three prairie provinces. In Alberta alone, an
ducting two surveys to estimate nest occupancy and pro- estimated 1702 pairs nested in 1992. There is some evi-
ductivity probably results in underestimates of nest oc- dence that a surplus of breeders exists, although much of
cupancy and nest failure and overestimates ofnest success. the former breeding range is still vacant. The purpose of
Surveys must be planned with a good knowledge of local this presentation is to evaluate to what degree management
nesting chronology to minimize these errors. efforts have contributed to halting or reversing this species’
decline.
Morphological Variation in Migratory
Red-tailed Hawks (Buteo jamaicensis) from the
Preliminary Eggshell Thickness and Contaminant
Goshute Mountains of Nevada and the Manzano
Analysis of Urban Nesting Peregrine Falcons in
Mountains of New Mexico
Wisconsin
Schmidt, E.V. Department of Biological Sciences, Uni- Septon, G. Milwaukee Public Museum, 800 West Wells
versity of NeNvVada, Las Vegas, 4505 Maryland Parkway, Street, Milwaukee, WI 53233 U.S.A. J.B. Marks. Wis-
Las Vegas, 89154-4004 U.S.A.
consin Peregrine Society, P.O. Box 1148, Milwaukee, WI
Because of the tendency of raptors to show fidelity to 53201-1148 U.S.A.
birthplace despite migratory habits, it is hypothesized that Since 1989, addled and infertile peregrine falcon {Falco
red-tailed hawks {Buteo jamaicensis) using two separate
peregrinus) eggs have been salvaged from urban nest sites
flyways come from distinct populations. DifTerences in in Wisconsin. They have been measured and weighed to
selection pressures such as migratory habits, prey differ-
determine the “Ratcliffe thickness index” and the contents
ences, and temperature/humidity gradients may serve to
have been analyzed for organochlorines and heavy metals.
maintain unique morphological characteristics within The results of these tests will serve both as baseline data
populations. Multivariate and univariate statistics are used
for the recovering peregrine falcon population in Wiscon-
to provide information on patterns of morphological vari-
sin and as a measurement gauge for comparisons of egg-
ation in migratory red-tailed hawks which were trapped
shell statistics from other geographic populations.
in the Goshute Mountains of Nevada and the Manzano
Mountains ofNew Mexico. A principle components anal-
ysis indicated that red-tails were significantly different in Red-shouldered Hawk Reproductive Success Along
one “shape” component between flyways. Hatch-year red-
THE Upper Mississippi River During Record
tails were also found to be significantly different when
Flooding in 1993
analyzed character by character using univariate statistics.
Red-tailed hawks which use different flyways were found Stravers, J.W. Midwest Raptor Research Fund, P.O
to be significantly different (P < 0.1) for wing chord, Box 32, Pella, IA 50219 U.S.A.
hallux length, tarsus length and tarsus width measure- We
monitored 27 of the 35 known red-shouldered hawk
ments. Results for red-tailed hawks can be compared with
{Buteo lineatus) nesting sites along a 369-mile stretch of
other migratory birds which use the same routes for an
the Upper Mississippi River from Wabasha, Minnesota,
understanding of population structure and variation that
to Burlington, Iowa, during 1993 when the river reached
results from natural selection on populations from differ-
record high levels at most locations. Of 18 red-shouldered
ent habitats.
hawk (RSH) nesting attempts, only seven were successful,
or at least produced nestlings. The remaining eleven nest-
Ferruginous Hawk Management: ing attempts were aborted or failed to produce nestlings
Was it for the Birds? Although a total of 15 nestling RSH reached fledging age,
at least nine drowned or failed to survive their first flight.
SCHMUTZ, J.K. Department ofBiology, University ofSas- Dangerously high waterlevels and U.S. Coast Guard boat-
katchewan, Saskatoon, SK S7N OWO Canada ing restrictions kept us from determining the final outcome