128. 
129. 
130. 
from several sources concerning osprey 
breeding success in Minnesota. Rec- 
ords indicate that human disturbance 
is a significant factor in reducing 
osprey productivity. Disturbances by 
direct shooting and by chilling or 
overheating of eggs when adults are 
frightened from nests are recorded. 
DISTURBANCE (GENERAL), FORESTS, OSPREY 
Dunstan, T. C. 1973. 
ospreys in Minnesota. 
113. 
The biology of 
Loon 45:108- 
Results of 10 years of osprey research 
are summarized. While the effects of 
human disturbance on osprey productiv- 
ity are difficult to evaluate, obser- 
vations suggest that ospreys are sen- 
sitive to human interference, espe- 
cially during incubation. Some nest 
abandonments have followed increased 
summer recreational use of the areas 
by boaters and fishermen. 
BOATING, FISHING, RESEARCH IMPACTS, FOR- 
ESTS, LAKES, OSPREY 
Dunstan, T. C., J. E. 
F. Harper. 1975. 
eagles in Minnesota. 
Mathisen, and J. 
The biology of bald 
Loon 47:5-10. 
Among aspects of the biology and be- 
havior of bald eagles described are 
the effects of environmental contami- 
nants and human disturbance on eagle 
productivity. An investigation by J. 
E. Mathisen showed that disturbance in 
the mid-1960's was within the toler- 
ance limits of eagles, but another 
later study found evidence of reduced 
eagle productivity associated with 
disturbance. Increased snowmobile use 
is bringing more people into remote 
areas where eagles winter, and the ef- 
fects on eagles are unknown. 
DISTURBANCE (GENERAL), OFF-ROAD VEHI- 
CLES, FORESTS, THREATENED AND ENDANGERED 
SPECIES, U.S. NATIONAL FORESTS, BALD 
EAGLE 
Dwernychuk, L. W., and D. A. Boag. 1972. 
How vegetative cover protects duck 
nests from egg-eating birds. J. 
Wildl. Manage. 36:955-958. 
The importance of vegetative cover in 
protecting duck nests from avian pre- 
dators was studied in Alberta. Human 
26 
131. 
ae. 
133. 
disturbance can lead to egg predation 
when adults are flushed from nests, 
but avian predators located even well- 
hidden artificial nests. Disturbance 
of vegetation around nests by humans 
apparently provides a visual clue aid- 
ing avian predators in locating unat- 
tended duck nests. 
DISTURBANCE (GENERAL), 
PREDATION, WATERFOWL, 
CALIFORNIA GULL, 
BILLED MAGPIE 
LAKES, WETLANDS, 
RING-BILLED GULL, 
COMMON CROW, BLACK- 
Eckstein, R. G., T. F. 
Rongstad, and J. G. Bollinger. 
Snowmobile effects on movements of 
white-tailed deer: A case-study. En- 
viron. Conserv. 6:45-51. 
O'Brien, O. J. 
1979. 
Effects of snowmobiles on winter home 
ranges, movements, and activity pat- 
terns of white-tailed deer were stud- 
ied in Wisconsin. Daily activity pat- 
terns, home range size, and habitat 
use were little affected by snowmo- 
biles. The impact of snowmobiles on 
deer appears to be minimal, but rout- 
ing trails away from deer concentra- 
tion areas in winter is suggested. 
OFF-ROAD VEHICLES, HARASSMENT, FORESTS, 
FLIGHT DISTANCE, RECREATION MANAGEMENT, 
U.S. NATIONAL FORESTS, WHITE-TAILED DEER 
Eckstein, R. G., and O. J. Rongstad. 
1973. Effects of snowmobiles on the 
movements of white-tailed deer in 
northern Wisconsin. Proc. Midwest 
Fish Wildl. Conf. 35:35-39. 
Studies in northern Wisconsin evalu- 
ated the effects of snowmobile use on 
white-tailed deer in wintering yards. 
Movements and activities of telemeter- 
ed deer were compared between a yard 
receiving snowmobile use and one with 
no use. Some deer showed avoidance of 
snowmobile trails while the machines 
were present, but no-— significant 
changes in home range size or daily 
movement patterns were observed. 
OFF-ROAD VEHICLES, 
WHITE-TAILED DEER 
HARASSMENT, FORESTS, 
Elder, J. M. 1977. Human interactions 
with Sierra Nevada bighorn sheep: The 
Mount Baxter herd. M.S. Thesis. Uni- 
Ann Arbor. 93 
versity of Michigan, 
Ppp. 

