Breeding bird monitoring in Great Lakes National Forests: 1991-2001

Abstract

• A total of 135, 168, and 133 stands (1,268 survey points) were surveyed for breeding birds in the Chippewa, Superior, and Chequamegon National Forests, respectively. Eleven years of surveys have been completed in the Chippewa and Superior NF, and ten years in the Chequamegon NF. • Breeding bird surveys in the St. Croix region of Minnesota have been conducted over the past ten years at 171 points. Surveys in southeast Minnesota have been conducted over the past seven years at 211 points. • We were able to examine trends in abundance for 77 bird species in at least one of the five study areas. Fifty species in the Chequamegon NF, 49 species in the Chippewa NF, 41 species in the Superior NF, 39 species in the St. Croix region, and 40 species in Southeast Minnesota were tested for population trends. Thirty- five species were also tested for a regional trend (three national forests combined). • Twenty-six species increased significantly (P > 0.05) in at least one study area and 32 species decreased. Two species had highly significant (P < 0.01) increasing trends in multiple study areas, and seven species had highly significant decreasing trends in multiple study areas. Four species had significant increasing regional trends and 11 had decreasing trends. • The most convincing increasing trends were those of the Red-breasted Nuthatch and American Redstart regionally and in the Chippewa NF, Yellow-bellied Sapsuckcer and Yellow-bellied Flycatcher in the Chequamegon NF, the Chestnutsided Warbler in the Chippewa NF, the Northern Parula in the Superior NF, and the Least Flycatcher in the St. Croix region. Eight other species had highly significant trends in southeastern Minnesota, albeit with a shorter time span than the northern sites. • The most convincing decreasing trends are those of the Eastern Wood-Pewee, Winter Wren, Ovenbird, Scarlet Tanager, and Song Sparrow regionally, the Eastern Wood-Pewee in the Chequamegon and Superior NF, the Winter Wren in the Chequamegon NF, the Song Sparrow in the Chippewa NF, the Hermit Thrush in the Chequamegon and Chippewa NF, and the Black-and-white Warbler in the Chequamegon NF, Superior NF and St. Croix region. The Brown-headed Cowbird decreased in southeastern Minnesota during the six years of monitoring there. • The percentage of increasing species in each study area ranged from 13% in St. Croix, MN study area to 28% in Southeast MN. The percentage of decreasing species ranged from 20% in Southeast MN to 31% in the Chippewa NF. Over half the species in each study area had a non-significant trend (P > 0.05). • There are 17 instances where a species showed a significant increase in a particular study area in results from 2000, with no increase noted in 2001, and 11 instances where a species was not increasing in 2000 and is increasing in 2001. Conversely, there are five instances where a decreasing species in a particular study area from 2000 is no longer showing a significant decrease, and 25 instances where a species was not decreasing in 2000 and is decreasing in 2001. • Ten of the 35 species that were tested for a regional trend had similar trends on Breeding Bird Survey routes. One species had an increasing regional trend and an increasing BBS trend, three species had decreasing trends on both, and six species had non-significant trends on both. • When compared to all species tested, ground nesters were more prevalent among decreasing species (33% vs. 48%) and less prevalent among increasing species (33% vs. 19%), however the differences were not statistically significant (P = 0.069). Evidence from other regional studies have demonstrated greater nest predation rates on ground nests near forest edges, as well as a significant increase in the creation of forest edges in recent years. Landscape fragmentation and nest predation may be having negative effects on declining ground-nesters such as the Winter Wren, Hermit Thrush, Black-and-white Warbler, Ovenbird, and Song Sparrow. • Averaged over all study areas, 10.6% of the points have been harvested since the beginning of monitoring, which is about 1% a year. This is comparable to the 4.8% change from mature forest to early-successional types on federally managed forest lands in northeastern Minnesota between 1990 and 1995.