Breeding bird monitoring in Great Lakes National Forests: 1991-2006

Abstract

• A total of 132, 133, and 164 stands (1,254 survey points) were surveyed for breeding birds in the Chequamegon, Chippewa, and Superior National Forests (NF), respectively in 2006. Annual surveys have been conducted since 1991 in the Chippewa and Superior NF, and since 1992 in the Chequamegon NF. • Comprehensive surveys of vegetation structure were carried out on 93, 74, and 63 points in the Chequamegon, Chippewa, and Superior NFs, respectively, on over 50 observer-days of sampling. Monitoring personnel on the Chippewa and Superior NFs provided excellent assistance in the coordination and completion of this effort. • Trends in relative abundance were calculated for 72 bird species, including 57 species in the Chequamegon NF, 57 in the Chippewa NF, and 49 in the Superior NF. Thirty-nine species were also tested for a pooled trend by combining data from the three national forests. • A total of 163 species/national forest trends were calculated in 2006 (not including pooled trends), 68 (42%) of which were significant (P ≤ 0.05). Twenty three species increased significantly (P ≤ 0.05) in at least one national forest and 24 species decreased. Eleven species had significant increasing pooled trends and 11 had decreasing trends. Of the 158 species/national forest trends calculated in 2005, 19 (12%) changed in 2006. • The percent of increasing species on each national forest ranged from 9% in the Chequamegon NF, to 25% in the Chippewa NF. The percent of decreasing species ranged from 20% in the Superior NF, to 28% in the Chequamegon NF. • The short-distance migrant guild showed highly significant declines on all national forests. Long-distance migrants also declined on all national forests. Permanent residents increased on the Chippewa and Superior NF and in the pooled NFs, but were stable on the Chequamegon NF. • The ground nesting guild showed highly significant declines on all national forests. Shrub/sub-canopy nesters increased on Chippewa NF, but were stable in Chequamegon and Superior NFs. Canopy nesters increased in Chquamegon NF and cavity-nesters increased in Chippwa and Superior NFs. All nesting guilds showed significant trends in the pooled NFs with increases in shrub/subcanopy-nesters and cavity-nesters and decreases in ground- and canopy-nesters. • The deciduous and mixed forest bird guilds declined on the Chequamegon and Superior NFs and the pooled NFs. The lowland coniferous forest bird guild declined on the Chippewa NF and the pooled NFs. The early-successional bird guild increased on the Chippewa NF and the upland coniferous bird guild increased on the Chippewa and Superior NFs as well as in the pooled NFs. • Evidence from previous regional studies have demonstrated greater nest predation rates on ground nests near forest/clearcut edges, as well as a significant increase in the creation of forest edges in recent years. Increasing amounts of forest edge and nest predation may be having negative effects on declining ground-nesters such as the Winter Wren, Veery, Hermit Thrush, Ovenbird, and White-throated Sparrow. • Of the 1274 survey sites on the three national forests, 15.5% have been at least partially harvested since the beginning of monitoring, which is about 1% a year. This harvest rate is comparable to the documented 4.8% change from mature forest to early-successional types on federally managed forest lands in northeastern Minnesota between 1990 and 1995 (i.e., ~1% annual change). Thus, it appears that management activities on our sample sites are representative of the national forests as a whole, and that the trends we are documenting are probably occurring across the regional landscape. • Many of the declining trends that we have detected appear to be consistent across years instead of being due to a few years with very low or high abundance. One of the main goals of this monitoring program is to identify potential declines of forest bird species, especially for species of conservation concern such as the Eastern Wood-Pewee, Winter Wren, Hermit Thrush, Ovenbird, and White-throated Sparrow. The declines observed over the past years for common species such as the Ovenbird and White-throated Sparrow are a continuing concern and special management consideration should be given to these species.