Tennessee Warbler (Vermivora peregrine) Vincent S. Cavalieri
Crane Creek State Park, OH (View comparison of Atlas I & II) © Darlene Friedman The Tennessee Warbler, like other Neotropical The Tennessee is a long-distance migrant migrant species is a bird of two worlds, wintering from southern Mexico through spending its life migrating between the Central America and into northern South extensive boreal forests of Canada and the America. Most spring migrants seemingly cross tropical habitats of southern Mexico, Central the Gulf of Mexico and then spread out across and South America. It was during this the central and northeastern United States and migration when the great nineteenth century then into Canada (Rimmer and McFarland ornithologist Alexander Wilson collected the 1998). The fall migration tends to be more first Tennessee Warbler along the Cumberland easterly (Dunn and Garrett 1997). River in Tennessee, thus giving the bird its name. On its breeding grounds the Tennessee Distribution Warbler is a spruce budworm specialist, shifting In Michigan the Tennessee Warbler occurs areas of occurrence and abundance to match the almost exclusively in the UP where the outbreaks of the budworm. preferred habitat of extensive forested bogs can be found (Binford 1991). Even in the UP it is a The Tennessee Warbler breeds across the boreal relatively rare species, occurring at the very forest zone of Canada, from British Columbia southern edge of its breeding range. Only areas and the Northwest Territories in the west, across with relatively extensive spruce bogs are to Newfoundland and the Maritime Provinces in occupied by breeding Tennessee Warblers in the the east. In the United States the Tennessee UP and even some seemingly suitable habitats breeds in a small part of southeastern Alaska do not support the species (Binford 1991). The and just barely makes it into the northern tier of Tennessee is a similarly rare breeder in states, primarily in northern Minnesota, the Wisconsin and New York, occurring only in the Upper Peninsula of Michigan, the Adirondack far northern parts of those states where Mountains of New York and northern New coniferous bogs and other boreal habitats occur England (Rimmer and McFarland 1998). (Wood 2006, Peterson 2008). During the Wisconsin atlas period there were no breeding
© 2011 Kalamazoo Nature Center Tennessee Warbler (Vermivora peregrine) Vincent S. Cavalieri confirmations, leading credence to its status as a boreal forests. The Tennessee Warbler rare breeder in our region, though summering fluctuates in numbers and areas of occurrence as males were recorded in some of the more boreal it responds to these outbreaks. Densities of northern parts of the state (Wood 2006). In Tennessee Warblers can increase dramatically Ontario the species is much more widespread, in areas of outbreaks (Ehrlich et al. 1988, particularly in the northern parts of the province Rimmer and McFarland 1998, Wood 2006, in the Canadian Shield and Hudson Bay Crins 2007). Lowlands where there are extensive boreal forests (Crins 2007). Abundance and Population Trends (Click to view trends from the BBS) Breeding Biology The population of Tennessee Warbler has been The Tennessee Warbler breeds in boreal forest estimated at around sixty million birds. Of habitats. In Michigan and Ontario they these approximately 16,000 are estimated to particularly prefer coniferous bogs dominated breed in Michigan (PIF Landbird Population by spruce and tamarack (Binford 1991, Rimmer Estimates Database 2009). While this is a very and McFarland 1988). These forests are small percentage of the total breeding typically described as open or “park-like” and population, Michigan trails only two other states often have openings with shrub stage willows, in estimated numbers of breeding Tennessee birches and alders (Binford 1991, Rimmer and Warblers, with the vast majority of the McFarland 1998). In other parts of their range population breeding in Canada (PIF Landbird they use “shrub scrub” types of habitats where Population Estimates Database 2009). As an small deciduous shrubs are found within indicator species for semi-open boreal forests, coniferous forests or along riparian areas (Dunn presence and numbers of Tennessee Warblers and Garrett 1997, Rimmer and McFarland could be used to measure the health of this rare 1998). habitat type in Michigan (Benyus 1989). The Tennessee Warbler continues to be a rare The nest of these species is placed on the species in Michigan. Atlas workers for MBBA ground, typically in a mound of sphagnum moss II found very similar numbers to MBBA I. at the base of a fallen tree, overturned stump, or They found Tennessee Warblers in 9% of next to a small shrub (Ehrlich et al. 1988, townships in the UP, which is exactly the same Rimmer and McFarland 1998). These nests, as during MBBA I. Outside the boreal forests which are often very well concealed, are usually of the UP there continues to be very little in a small clearing in the boreal forest or on the evidence of breeding Tennessee Warblers in margin of a bog. They are often associated with Michigan, with less than 1% of townships in the alder or willow shrubs (Rimmer and McFarland NLP having Tennessee Warbler observations, 1998, Wood 2006). The Tennessee Warbler including no sightings of this species outside the like several other boreal forest breeding warbler UP during MBBA II. In addition the Tennessee species, specializes on exploiting outbreaks of Warbler sometimes lingers far south of the the spruce budworm, a moth species that has breeding range well into June and sometimes periodic outbreaks in different areas of the fall migrants begin to filter back through the region in early July. This almost continuous
© 2011 Kalamazoo Nature Center Tennessee Warbler (Vermivora peregrine) Vincent S. Cavalieri stream of migrants passing through the area (Rimmer and McFarland 1998). Another during the breeding season, makes determining concern is replanting of boreal forests with jack true breeding status that much more difficult pine and black spruce instead of balsam fir, a (Binford 1991, Wood 2006). change that could lead to decreased budworms and thus less forage for Tennessee Warblers. In BBS data shows that Tennessee Warblers have addition, spraying insecticides to control experienced a survey wide 1.1% annual decline budworm outbreaks may have negative impacts since the BBS was initiated in 1966. From 1966 on Tennessee Warblers (Peterson 2008). to 1979 the Tennessee Warbler actually showed a 10.6% annual increase in population, however since 1980, they have shown a 7.5% annual decline (Sauer et al. 2008). It should be noted that interpreting BBS trends for this species can be difficult because few BBS routes occur in the core range of the Tennessee Warbler. In addition densities fluctuate based on spruce budworm outbreaks which can also make trend interpretations difficult (Crins 2007).
Conservation Needs The Tennessee Warbler may actually be more abundant now than in the nineteenth century because of the increased amounts of suitable habitats created by logging operations (Rimmer and McFarland 1998). Though there is some concern that overlogging, road construction and development could negatively impact this species (Binford 1991). In addition peat- harvesting and drainage could also degrade Tennessee Warbler habitat (Rimmer and McFarland 1998). The Tennessee Warbler is vulnerable to collisions with TV towers and other tall, lighted structures during migration (Rimmer and McFarland 1998). A potential problem on the wintering grounds is the conversion of shade grown coffee plantations to sun coffee systems, which could adversely affect this and other Neotropical migrant species. Maintaining rustic shade grown coffee plantations could be beneficial to this species
© 2011 Kalamazoo Nature Center Tennessee Warbler (Vermivora peregrine) Vincent S. Cavalieri
Literature Citations American Ornithologists' Union, Benyus, J.M. 1989. Northwoods Wildlife: A Washington, DC. Watchers Guide to Habitats. NorthWord. Sauer, J.R., J.E. Hines, and J. Fallon. 2008. Minocqua, WI. The North American Breeding Bird Survey, Binford, L.C. 1991. Tennessee Warbler. In results and analysis 1966-2007. Version Brewer, R., G.A. McPeek, and R.J. Adams 5.15.2008. USGS Patuxent Wildlife Jr. 1991. The Atlas of Breeding Birds of Research Center. Laurel, MD. Michigan. Michigan State University Press. Wood, C. 2006. Tennessee Warbler. In East Lansing, MI. Cutright, N.J., B.R. Harriman, and R.W. Crins, W.J. 2007. Tennessee Warbler. In Howe. 2006. Atlas of the Breeding Birds of Cadman, M.D., D.A. Sutherland, G.G. Beck, Wisconsin. Wisconsin Society for D. Lepage, and A.R. Couturier (eds.). 2007. Ornithology. Waukesha, WI. Atlas of the Breeding Birds of Ontario, 2001-2005. Bird Studies Canada, Environment Canada, Ontario Field Ornithologists, Ontario Ministry of Natural Resources, and Ontario Nature. Toronto, Ontario. Dunn, J.L., and L.O. Rosche. 1997. A Field Guide to Warblers of North America. Houghton Mifflin. New York. Erlich, P.R., D.S. Dobkin, D.S., and D. Wheye. 1988. The Birder’s Handbook: A Field Guide to the Natural History of North American Birds. Simon and Schuster. New York. Peterson, J.M.C. 2008. Tennessee Warbler. In McGowan, K.J., and K. Corwin. 2008. The Second Atlas of Breeding Birds in New York State. Cornell University Press. Ithaca, NY. PIF Landbird Population Estimates Database. Downloaded from
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