Cape May Warbler Habitat Model
go to: USFWS Gulf of Maine Watershed Habitat Analysis
go to: Species Table

Draft Date:
October, 2002

Species:
Cape May warbler, Dendroica tigrina

Use of Study Area Resources:
Reproduction. "...northeastern British Columbia and southern Mackenzie to northern Saskatchewan and Nova Scotia, south to central Alberta, central Saskatchewan, northwestern North Dakota, northeastern Minnesota, northern Wisconsin, eastern New York, and northern New England (Baltz and Latta 1998)" (Robertson and Hammerson 2001).  Winters on Caribbean islands and Central American tropics (Robertson and Hammerson 2001, Nearctica).

Habitat Requirements (Reproduction):
Cover:  "..is found in open spruce forests, although during the spring and autumn migrations it occurs in a variety of wooded habitats." (Nearctica). "Primarily in forests of spruce (PICEA spp.) and/or fir (ABIES spp.), typically in stands 50 years old, 15 m tall, with well developed crowns and some trees that rise above canopy for use as singing posts (AOU 1998, Rosenberg and Hodgeman 2000, Baltz and Latta 1998, Baker 1978, Welsh 1987, Semenchuk 1992). Trees may be scattered or dense; also found near forest edge, especially if birches or hemlocks are present and more open land with small trees (DeGraaf and Rappole 1995)" (Robertson and Hammerson 2001).

"In Michigan, found in wet coniferous bogs dominated by black spruce (Baker 1978, L.C. Binford in Brewer et al. 1991). In New York, occupies stands of medium aged spruce (25-75 years old), with some balsam fir (J. M. C. Peterson in Andrle and Carroll 1988). In Maine, uses various coniferous forest stands, including second-growth balsam fir and red spruce (P. rubens) with an open understory (Morse 1978)." (Baltz and Latta 1998).

Foraging: Feed on insects: moths, flies, beetles, ants, (Nearctica, DeGraff and Rudis 1983). "Proliferates in areas heavily infested by spruce-budworms, and may not occur after the outbreak has subsided (Brewster 1938, Erskine 1977, Morse 1989)" (Robertson and Hammerson 2001).

Management Concerns:  "In areas such as the spruce-hardwood region of the northeastern U.S. and southeast Canada that are heavily logged, the continued loss of mature forest may contribute to long-term declines in this species." (Robertson and Hammerson 2001).

Model:
The Breeding Bird Atlas (BBA) data for Maine, New Hampshire and Massachusetts (courtesy of the University of Vermont COOP Unit) were used to identify the range of the Cape May warbler within the study area.  BBA blocks and Breeding Bird Survey (BBS) sites in which Cape May warblers were known to occur were used to select USDA Forest Service Ecological subunits (Keys et al. 1995); habitat mapping then was restricted to these areas.

The preferred vegetation for Cape May warblers appears to be somewhat open upland and wetland coniferous forest, or coniferous bogs. In order to gain more specific information within the study area, we inspected conditions at Cape May warbler occurrence sites based on 1990 BBS data (courtesy of Raymond O'Connor, Univ. of Maine).  We observed that most sites had at least some palustrine coniferous forest, or upland coniferous forest which adjoined freshwater wetlands.

Based on the sources and our BBS findings, we included as habitats 1) all wetland coniferous forest; 2) upland coniferous and mixed forest adjoining wetland cover types (see table, below).

NWI Designations (wetlands only)	Cover Types	Cover Suitability (0 - 1 scale)
	Upland deciduous forest
	Upland coniferous forest	1.0*
	Upland mixed forest	1.0*
	Grassland
	Upland scrub/shrub
	Cultivated
	Developed
	Bare ground
PEM, L2EM	Lake/pond, emergent vegetation	**
PFOcon	Palustrine forest, conifer	1.0,**
PFOdec	Palustrine forest, deciduous	**
PSSdec	Palustrine scrub shrub, deciduous	**
PSScon	Palustrine scrub shrub, conifer	**
PAB, L2AB	Lake/pond, aquatic vegetation
L1UB, PUB	Lake/pond, unconsolidated bottom
L2US	Lake, unconsolidated shore
L2RS	Lake, rocky shore
R1UB	Riverine subtidal unconsolidated
Rper	Riverine perennial
E1AB	Estuarine subtidal vegetated
E1UB	Estuarine subtidal unconsolidated bottom
E2AB	Estuarine intertidal algae
E2EM	Estuarine intertidal emergent
E2RS, R1RS	Estuarine, tidal river rocky shore
E2SS	Estuarine intertidal shrub
E2US	Estuarine intertidal unconsolidated shore
M1AB	Marine subtidal vegetated
M1UB	Marine subtidal unconsolidated bottom
M2AB	Marine intertidal algae
M2RS	Marine intertidal rocky shore
M2US	Marine intertidal unconsolidated shore
NOTES	*if adjoins any types marked '**' **if adjoins coniferous forest

Model testing: Cape May warbler occurrences from 1997 through 2000 along Breeding Bird Survey routes were used to test the habitat map from the above model. We compared the presence of habitat near these sites to that for a random set of 658 upland points within the species range. Of the 37 sites with birds, 32 had mapped habitat, while 438 sites out of the 658 randomly distributed sites had habitat. Birds occurred in areas mapped as having habitat more frequently than would be expected by chance (Chi-square significant at < .0102).

Sources:

Baltz, M.E. and S.C. Latta. 1998. Cape May Warbler Dendroica tigrina. In A. Poole and F. Gill, (eds.) The Birds of North America, No. 332. The Academy of Natural Sciences, Philadelphia, and The American Ornithologists' Union, Washington, D.C.

DeGraaf, R.M. and D.D. Rudis. 1983. New England Wildlife: Habitat, Natural History and Distribution. USDA Technical Report NE-108.

Nearctica. Warblers of Eastern North America.  http://www.nearctica.com/birds/warbler/Dtigr.htm downloaded 10/29/01

Keys, J.E., Jr., J.C. Carpenter, S. Hooks, F. Koenig, W.H. McNab, W. Russell and W. Smith. 1995. Ecological units of the eastern United States - first approximation (map and booklet of map unit tables), USDA Forest Service. Atlanta, GA.

Robertson, B., and G. Hammerson. 2001. Species Management Abstract: Cape May Warbler (Dendroica tigrina). THE NATURE CONSERVANCY, 4245 North Fairfax Drive, Suite 100, Arlington, VA 2220; downloaded 11/01.