Warbling Vireo (Vireo Gilvus) Mike Bishop

Warbling Vireo (Vireo gilvus) Mike Bishop

Magee Marsh Wildlife Area, Ottawa Co., OH 5/11/2006 © John Van Orman This species sponsored by Loretta Gold.

(Click to view a comparison of Atlas I to II)

The distinctive, yet un-vireo-like, song of the coincides with the change in the coniferous Warbling Vireo is commonly heard in wet component of the forests in the state. meadows and early successional woodlands around wetlands and watercourses as well as The percentage of townships that exhibited edge habitat associated with mature mixed detections increases dramatically from the UP to deciduous woodlands (Gardali and Ballard the SLP. Warbling Vireos were detected in only 2000). These are the preferred habitat of this about 19% of townships surveyed in the UP non-descript vireo. Consequently, it is found compared with about 64% and 90% in the NLP throughout the state in stable numbers in and SLP, respectively. Breeding confirmations habitats that often include parks and suburban followed suit with UP townships exhibiting only neighborhoods as well as more undisturbed 1.9% and the NLP showed 3.3%. The SLP with locations. Like the better-known Red-eyed a greater abundance of appropriate breeding Vireo, the Warbling Vireo is a canopy species habitat, had 10.3% of its townships giving that forages and nests well above the ground. breeding confirmations. With a broad range that extends from the western U.S. and Canada and east through the From the first Michigan atlas to the second all Midwest and into the northeastern U.S., three regions showed very slight decreases in Michigan marks the northern limits of the the number of blocks exhibiting breeding Warbling Vireo’s breeding range in the determinations. Possible and Confirmed Midwest. designations decreased for all three regions, although by only a small percentage. Probable Distribution designations increased for all three regions, Fairly common throughout its range, the again only slightly. Most notable was a Warbling Vireo prefers deciduous woodlands decrease by nearly one-half in the number of that are relatively open and associated with confirmations for the SLP between MBBA I and water. Coniferous stands seem to be avoided. MBBA II. Consequently, in Michigan, the Warbling Vireo is better represented in the LP than the UP. Because their nests are difficult to detect and Furthermore, in the LP it is more widely observe, a low number of townships reported distributed in the SLP than the NLP. This breeding confirmations (5.4%). However, the

© 2010 Kalamazoo Nature Center Warbling Vireo (Vireo gilvus) Mike Bishop strong demonstration of singing males (which continues to take advantage of human-modified often sing at the nest) throughout the breeding habitat. season suggests a high percentage of nesting pairs. Possible and Probable breeding Determining whether these changes are determinations for all townships were at 27.3% significant remains to be seen. However, and 26.2% respectively. In the SLP, where the differences in data collection between the two abundance of warbling vireos is highest, the atlases cannot be ruled out as having possibly percentage of Possible and Probable breeding produced the changes. How this might affect determinations was 31.6% and 47.8% perceived differences in data between the two respectively. atlases or between atlas data and BBS data probably cannot be quantified. Breeding Biology Warbling Vireos arrive in Michigan during the Conservation Needs first week of May and nesting begins around the As with all of our songbirds, pressure from nest end of the month (Hull 1990). A single brood is predators and nest parasites (Brown-headed fledged around the fourth of July and fall Cowbird) and impacts on the quality of the migration begins in late August. Warbling wintering grounds could affect Warbling Vireo Vireo nests are the typical woven, open-cup nest numbers throughout its range. Additionally, of most vireos and are located at a height of 10 being a nocturnal migrant, collisions with to 15 m. Females usually lay about four eggs buildings, cell towers, and wind turbines, will which they incubate for approximately 13 days. continue to pose a threat to Warbling Vireo Nestlings fledge when they are about 10-19 abundance (Graber et al. 1985, Stevenson and days old (Gardali and Ballard 2000). Anderson 1994). More specifically, it is likely that as wooded areas of Michigan become more Abundance and Population Trends mature and develop a more extensive closed (Click to view trends from the BBS) canopy, available breeding habitat for Warbling Warbling Vireo detections are greatest in the Vireo will become more limited. southern half of the LP and decrease as one moves north to the UP. This has not changed since the first atlas (Brewer et al 1991). This clearly reflects the lack of appropriate breeding habitat as one moves north in the state. According to the BBS data for Warbling Vireo in Michigan, there has been an almost imperceptible and insignificant decline (-0.16%) in abundance (Sauer et al. 2008). The abundance of the Warbling Vireo in the entire USFWS Conservation Region 3, in which Michigan is included, showed a very slight statistically significant increase (1.21%). Both the Ontario and New York breeding bird atlases showed very similar changes for Warbling Vireo between their first and second atlases (James 2007, McGowan 2008). Overall this would indicate a population that is relatively stable. This makes sense as the species

Literature Citations Brewer, R., G.A. McPeek, and R.J. Adams Jr. (eds.). 1991. The Atlas of Breeding Birds of Michigan. Michigan State University Press. East Lansing, MI. Gardali, T and Ballard, G. 2000. Warbling Vireo (Vireo gilvus). In Birds of North America, No. 551 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA. Graber, J.W., R.R. Graber, and E.L. Kirk. 1985. Illinois Birds: Vireos. Biology Notes No. 68. Illinois Natural History Survey. Urbana, IL. Hull, C. 1991. Warbling Vireo. In Brewer, R., G.A. McPeek, and R.J. Adams Jr. (eds.). 1991. The Atlas of Breeding Birds of Michigan. Michigan State University Press. East Lansing, MI. James, R. 2007. Warbling Vireo. In Cadman, M.D., D.A. Sutherland, G.G. Beck, D. Lepage, and A.R. Couturier (eds.). 2007. 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. McGowan, KJ. 2008. Warbling Vireo. In McGowan, K.J., and K. Corwin (eds.). The Second Atlas of Breeding Birds in New York State. Cornell University Press. Ithaca, NY. Sauer, J.R., J.E. Hines, and J. Fallon. 2008. The North American Breeding Bird Survey, Results and Analysis 1966-2007. Version 5.15.2008. USGS Patuxent Wildlife Research Center, Laurel, MD. Stevenson, H.M., and B.H. Anderson. 1994. The Birdlife of Florida. University Press of Florida. Gainesville, FL.