Northern Forest Region

Description

The Northern Forest region includes the area around most of the Great Lakes, the Adirondacks of New York, northern New England, and the Canadian Maritime Provinces. It covers the area between the southern deciduous forests and the northern boreal spruce-fir forest. This region is at the northern limit of the Scarlet Tanager's distribution, and the species is generally less abundant here than in other regions.

The region is heavily forested throughout. The area surrounding the Great Lakes and along the Atlantic coast is characterized by relatively little relief with many rolling hills, most of glacial origin. Forests of this region are transitional between southern deciduous forests and the northern boreal spruce-fir forest. Deciduous forests tend to occur on favorable sites with good soils whereas coniferous forests are found on less-favorable sites with poor soils. Common tree species are yellow birch, sugar maple, American beech, white pine, and eastern hemlock (Bailey 1995). The mountainous areas of New York and New England have a vertical zonation of tree species. The valleys have deciduous forests of sugar maple, yellow birch, beech, and some hemlock. The lower slopes have mixed forests of spruce, fir, maple, beech, and birch. Finally, pure stands of balsam fir and red spruce can be found above the mixed-forest zone (Bailey 1995).

Forest Types and Tree Species

Sixty-six percent of Project Tanager study sites were located in mixed deciduous/coniferous forests with the remainder in deciduous forests (32%) and coniferous forests (2%). The distribution of sites with breeding Scarlet Tanagers was similar: 60% mixed deciduous/coniferous, 39% deciduous, and 1% coniferous. The most common trees present on Project Tanager study sites were maples (66% of sites), oaks (55%), and pines (41%). Trees located at sites with breeding Scarlet Tanagers were similar but with slightly more oaks: maples (65% of sites), oaks (66%), and pines (38%).

Minimum-area Requirements

In the Northern Forest region, tanagers are predicted to occur in virtually any size forest patch within landscape blocks that are more than 70% forested; that is, the birds do not show area sensitivity in extensively forested landscapes. As the amount of forest in the surrounding landscape block decreases below 70%, the minimum area required by tanagers increases (Table 9). Because of the large amount of forest throughout this region, minimum areas required by tanagers and other species are generally smaller than in other regions. For example, only in landscapes that are less than 40% forested are patches more than 100 acres (40 ha) necessary to achieve high suitability for tanagers, and high-suitability habitats are attainable in landscape blocks with less than 20% forest.

Table 9. Minimum area required to provide high, moderate, or low habitat suitability for Scarlet Tanagers based on analysis of 66 study sites in the Northern Forest region (see Purpose and Use of Minimum Area Tables for definitions of habitat suitability).

Percentage of Forest
in 2,500-acre block Minimum area (acres) Required for

High Moderate Low

70 41 21 9

60 54 28 12

50 70 36 15

40 90 46 20

30 118 61 26

20 158 82 35

10 228 117 51

Scarlet Tanager Associates

Nine bird species of high conservation priority are associated with Scarlet Tanagers in the Northern Forest region (Table 10). Of these, the Veery, Black-and-white Warbler, Rose-breasted Grosbeak, and Yellow-bellied Sapsucker are the species most likely to benefit from habitat management for Scarlet Tanagers, as they occur at more than 50% of BBC plots that also support tanagers. Even though they are present at a lower percentage of plots, the Blackburnian Warbler, Wood Thrush, Canada Warbler, and Black-throated Blue Warbler also should be considered when developing habitat management strategies for Scarlet Tanagers in this region (Figure 12). Finally, in a slightly different analysis, we found that Scarlet Tanagers were present at 35% (9 of 26 plots) of BBC plots that reported Black-throated Blue Warblers.

Veery

Figure 12. The Veery is listed as a high-priority species by PIF in the Northern Forest region. Breeding Bird Survey data suggest that this species declined by 1.0% annually from 1966 to 1991. Veeries were present at 76% of BBC plots that also supported Scarlet Tanagers.
Photo by Mike Hopiak.

Table 10. These species may also benefit from habitat improvement for Scarlet Tanagers in the Northern Forest region. Species shaded with the darker color were included in the list because they occurred with Scarlet Tanagers on at least 75% of 51 Breeding Bird Census plots from 1932 to 1990. The remaining species were included because they are considered by PIF to be of high conservation priority in this region.

Species % Plots Conservation
Priority

Red-eyed Vireo 98 Low

Ovenbird 88 Low

Veery 76 High

Black-capped Chickadee 80 Low

Black-and-white Warbler 61 High

Rose-breasted Grosbeak 53 High

Yellow-bellied Sapsucker 53 High

Blackburnian Warbler 45 High

Wood Thrush 31 High, WL^a

Canada Warbler 29 High

Black-throated Blue Warbler 22 High, WL

Bay-breasted Warbler 10 High

^aWL—Also considered a Watch List species of global conservation concern (Carter et al. 1996)

Regional Summary

Because the Northern Forest region is extensively forested, the most effective strategy for sustaining populations of Scarlet Tanagers is to prevent landscape blocks from becoming too fragmented (in other words, maintain at least 70% forest), rather than managing the size of individual forest patches. For more information on improving habitat for Scarlet Tanagers in the Northern Forest region, contact the PIF Northeastern Regional Coordinator. PIF contact information can be found at www.PartnersInFlight.org.