EXECUTIVE SUMMARY FOR
RESOURCE MANAGEMENT REPORT 00-1
2000 BREEDING BIRD SURVEY AT ISLE ROYALE NATIONAL PARK, MICHIGAN
The importance of breeding bird surveys (BBS) has been illustrated by the longevity of the North American BBS program as well as the number of research projects that focus on declining neotropical migrant populations being conducted both in North America and abroad. Isle Royale National Park, Michigan, established a formal breeding bird survey in 1994 to integrate island population data with other studies being conducted in the region. This program has continued from 1995 to 2000 with the objective of determining and monitoring the size and composition of the neotropical migrant community on Isle Royale.
Point counts were conducted at Isle Royale NP from 12 June to 28 June 2000, using standardized transects on eight park trails. A total of 129 points were surveyed across the main island and on Passage Island. Species diversity values, representing the probability that two randomly drawn individuals will belong to different species, were calculated for each transect.
A total of 60 species (1442 individuals) were recorded. The number of species is average for the past several years, and the number of individuals is above the five-year average (1996-2000) of 1358. Overall, the number of species has remained similar between 1996 and 2000, while the number on individuals can fluctuate greatly from year to year. Fluctuation in yearly numbers has been recorded elsewhere in the region, as well as in Isle Royale's six years of breeding bird studies.
Four species (7% of total species) were present at all eight transects, while 16 species (27%) were recorded at only one transect. The highest number of species (37, or 62%) was recorded on both the Three Mile-Lane Cove and Ishpeming Trail transects, while the lowest number of species (8, or 13%) was recorded on Passage Island. Six species accounted for 48% of the total number of individuals recorded (White-throated Sparrow, Ovenbird, Nashville Warbler, Winter Wren, Black-throated Green Warbler, and Red-eyed Vireo).
Diversity values, by transect, ranged from 0.76 to 0.95 (on a 0-1 scale, which can be interpreted as a percentage) during the five-minute counts. Four transects decreased slightly in diversity, two increased slightly, while two stayed the same. Passage Island decreased significantly due to small numbers of points and species. Higher fluctuation with Passage Island diversity appears to be a prevalent component of this transect. The five year average for diversity values show a stable range of variation on six transects, with Passage Island and Windigo showing lower and more fluctuating diversity.
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