Breeding bird monitoring in Great Lakes National Forests: 1991-1998
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Breeding bird monitoring in Great Lakes National Forests: 1991-1998
Published Date
1999
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University of Minnesota Duluth
Type
Technical Report
Abstract
A total of 133, 162, and 128 stands (1,269 census points) were surveyed in the Chippewa, Superior and Chequamegon National Forests, respectively. Surveys have been completed for 8 years in the Chippewa and Superior and for 7 years in the Chequamegon.
One-hundred seventy census points were surveyed in East Central Minnesota over the past 7 years and 211 census points in Southeast Minnesota over the past 4 years.
A total of 74 species were abundant enough in at least one region to test for trends in annual abundance. Fifty species in the Chippewa National Forest, 45 species in the Superior National Forest, 50 species in the Chequamegon National Forest, 32 species in East Central Minnesota, and 38 species in Southeast Minnesota were tested.
The average number of species and individuals observed/stand or point in four of five study regions were at an all time high in 1998. In contrast, the lowest number of species and the second lowest numbers of individuals were observed in Southeast Minnesota in 1998 than in the previous three years.
A In the Southeast Minnesota region 57% of the species tested showed a significant trend in abundance. In the other four regions, 84 to 98% of the species tested exhibited a significant trend in abundance.
Almost 30% of the species in Southeast Minnesota showed significant linear decreasing trends from 1995 through 1998 and an additional 19% had negative overall trends. Ten percent of the species in Southeast Minnesota had increasing abundance trends.
In contrast, in the other four regions more than 63% (63 to 74%) of the species have increased in abundance from 1991 (or 1992) to 1998. The percent of the species that have declined in the other regions ranged from 25% in the Superior National Forest to 12% in the Chippewa National Forest.
A total of 38 species showed significant decreases (linear or other) in at least one region. Of these, 22 species (59%) also increased significantly in another region. Fifteen species decreased in one or more regions without indicating increases in other regions. Ten species declined in one region and six species, the Downy Woodpecker, Golden-crowned Kinglet, Gray Catbird, Canada Warbler, Indigo Bunting and American Goldfinch declined in two regions.
About 64% (7 of 11) of the permanent residents tested showed a significant decrease in one region. The proportion of short distant migrants that declined was about 40% (9 of 22) of the total number tested and about 55% (22 of 40) of the long distant migrants tested decreased in abundance in one region.
When species were categorized by nest location, the largest proportion of species decreasing were cavity and canopy nesting species.
The proportion (all about 50%) of species declining within general habitat groups was almost equal across open, young forest, and forest habitat groups.
The spring of 1998 was affected by the El Nino weather pattern and was warmer than average in all regions. Precipitation was lower in April than normal, but wetter than normal in the other spring months. June in all regions was cooler and wetter than normal.
The warm spring in the Great Lake’s area affected: 1) timing of permanent resident breeding which was earlier than normal, and 2) timing of short distance migrant arrival which was also earlier than normal. Arrival times of long distance migrants were not affected by local weather patterns.
We speculate that breeding of long distance migrants was also somewhat earlier in 1998. This is supported by the observations of more than the average number of fledglings during our late-June and early July survey dates.
It is also likely that more double brooding occurred in 1998 due to the favorable weather conditions, although we have no data to support this hypothesis.
Another potential reason for an increase in numbers of individuals in 1998 is also related to the warm spring weather and the theory of heterospecific attraction. Our data support this hypothesis: number of breeding migrants over the eight years of monitoring was highly correlated (r=0.701 and p< 0.001) with the number of foliage and bark gleaning insectivorous permanent residents. Specifically, in years where we observed the greatest numbers of Black-capped Chickadees, Red- and White-breasted Nuthatches and Blue Jays we also recorded the largest number of migrant individuals.
Four of the six species that decreased in abundance in more than one region (Gray Catbird, Canada Warbler, Indigo Bunting and American Goldfinch) are associated with early successional, edge, or shrub habitat.
Of the other two species that declined, the Downy Woodpecker occurs predominantly in mature deciduous forests and the Golden-crowned Kinglet is most abundant in mature lowland conifer habitat.
It is difficult to determine the exact cause of these species declines. However, more detailed studies may be required for these species if declines continue.
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1998 Annual Update Report; Report to: Chequamegon/Nicollet, Chippewa and Superior National Forests
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Natural Resources Research Institute, University of Minnesota Duluth
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Hanowski, JoAnn M; Niemi, Gerald J; Hawrot, Rita Y; Lima, Ann R. (1999). Breeding bird monitoring in Great Lakes National Forests: 1991-1998. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/187197.
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