Atlantic Coast Region

Description

The Atlantic Coast region includes all of the area between the Appalachian Mountains and the Atlantic Ocean. It stretches from the southern edge of Maine south to the boundary of the Scarlet Tanager's breeding range in Virginia and North Carolina. Relatively small forested areas located within a largely urban and suburban landscape characterize much of the region. This is especially true in the corridor between Boston and Washington, D.C. Some extensively forested areas occur in central Massachusetts, southern New Jersey, and Virginia. The forests of the northern part of the region are mostly deciduous, especially the Appalachian oak association. The dominant species are white oak and northern red oak. Pine-oak forests (pine barrens) are also found in dry sandy locations that are frequently exposed to naturally occurring fires (Bailey 1995). Oaks, hickories, sweetgum, blackgum, red maple, and winged elm are also common. Along the southern coast, evergreen oaks, laurels, and magnolias are common, while gum and cypress dominate coastal swamps. Savannas of pine forests with an understory of grasses and sedges (Bailey 1995) historically covered most upland areas in the southern portion of the region.

Forest Types and Tree Species

Fifty-eight percent of Project Tanager study sites were located in deciduous forests with the remainder (42%) in mixed deciduous/coniferous forests. The distribution of sites with breeding Scarlet Tanagers was the same: 58% deciduous and 42% mixed deciduous/coniferous. The most common tree species present on Project Tanager study sites were oaks (76% of sites), maples (64%), and pines (32%). Similarly, oaks, maples, and pines were present at 79%, 67%, and 30% of sites with breeding tanagers, respectively.

Minimum-area Requirements

In the Atlantic Coast region, tanagers are predicted to occur in virtually any size forest patch within landscape blocks that are more than 70% forested; that is, the species does 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 3). For example, as the amount of forest in a landscape is reduced from 50% to 40%, the minimum area required increases from 170 acres (68 ha) to 475 acres (190 ha). Note that in sparsely forested landscapes, the minimum areas required for high, moderate, or low suitability are sometimes impossible to achieve because the area of forest required exceeds the amount (%) of forest available in the 2,500-acre (1,000-ha) block.

Table 3. Minimum area required to provide high, moderate, or low habitat suitability for Scarlet Tanagers based on analysis of 136 study sites in the Atlantic Coast 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 21 4 1

60 62 11 2

50 172 31 5

40 476 86 14

30 NA^a 249 40

20 NA NA 129

10 NA NA NA

^aNot Available—acreage values exceed the amount of forest in the 2,500-acre block

Another way of assessing the suitability of a particular forest patch for tanagers is in terms of its isolation, or distance from larger tracts of contiguous forest. The suitability of small forest patches (less than 100 acres) increases if they are relatively close to larger tracts of contiguous forest (Table 4). For example, a 100-acre (40 ha) patch that is within one-half mile of the nearest large forest would be more than 70% as likely to support tanagers as an unfragmented forest. If the same patch, however, was greater than two miles from the nearest large forest, it would have less than a 40% chance of supporting tanagers when compared to an unfragmented forest.

Table 4. Probability of finding breeding Scarlet Tanagers in small forest patches (less than 100 acres) in relation to distance from nearest large forest in the Atlantic Coast region.

Distance From Small Patch to Large Forest Probability of Finding Tanagers Relative to Unfragmented Forest

100 yards 1.00

1/4 mile 0.88

1/2 mile 0.70

1 mile 0.55

2 miles 0.40

5 miles 0.28

10 miles 0.20

Scarlet Tanager Associates

Eight bird species of high conservation priority are associated with Scarlet Tanagers in the Atlantic Coast region (Table 5). Of these, the Wood Thrush and Eastern Wood-Pewee are the species most likely to benefit from management for Scarlet Tanagers, as they occur at more than 60% of BBC plots that also support tanagers. Even though they are present at a lower percentage of plots, the Acadian Flycatcher, Kentucky Warbler, Louisiana Waterthrush, and Yellow-throated Vireo should also be considered when developing habitat management strategies for Scarlet Tanagers in this region (Figure 10). It's also worth noting that Scarlet Tanagers were present at 67% (4 of 6 plots) of BBC plots that reported Cerulean Warblers and 56% (10 of 18 plots) of plots that reported Worm-eating Warblers.

Figure 10. The Yellow-throated Vireo is listed as a high-priority species in the Atlantic Coast region by PIF. This species is sometimes associated with forest edge habitat; however, breeding pairs require large blocks of forest or high percentages of regional forest cover to breed successfully. Yellow-throated Vireos were present at 22% of BBC plots that also supported Scarlet Tanagers.
Photo by Mike Hopiak.

Table 5. These species may also benefit from habitat improvement for Scarlet Tanagers in the Atlantic Coast region. Species shaded with the darker color were included in the list because they occurred with Scarlet Tanagers on at least 75% of 59 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

Ovenbird 85 Low

Wood Thrush 83 High, WL^a

Red-eyed Vireo 80 Low

Tufted Titmouse 75 Low

Eastern Wood-Pewee 63 High

Acadian Flycatcher 41 High

Kentucky Warbler 30 High, WL

Louisiana Waterthrush 25 High

Yellow-throated Vireo 22 High

Cerulean Warbler 7 High, WL

Kentucky Warbler 26 High, WL

Whip-poor-will 3 High

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

Regional Summary

According to the Breeding Bird Survey, Scarlet Tanagers have declined significantly during the past 30 years in the Mid-Atlantic Coastal Plain and Southern New England. The Scarlet Tanager is considered a moderate conservation priority by PIF in these regions. The Atlantic Coast region, like the Midwest region, is sparsely forested and heavily fragmented. Unlike the Midwest region, however, much of the fragmentation in the Atlantic Coast region is caused by development. Fragmentation caused by development, as opposed to agriculture, seems to be more detrimental to forest-dwelling birds. Furthermore, it's very difficult to establish forest corridors and restore forest habitat in extensively developed landscapes. The best strategy for sustaining populations of Scarlet Tanagers in this region is to protect existing forest through careful, long-term management that limits development in forested areas. In more rural areas, establishing forested corridors and restoring forest land might also prove beneficial. For more information on improving habitat for Scarlet Tanagers in the Atlantic Coast region, consult Bushman and Therres (1988), Hamel (1992), and Maryland Partners in Flight (1997); or contact the PIF Northeastern or Southeastern Regional Coordinators. PIF contact information can be found at www.PartnersInFlight.org.