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Blue-Gray Gnatcatcher (Polioptila Caerulea)

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Blue-Gray Gnatcatcher (Polioptila Caerulea) Blue-gray Gnatcatcher (Polioptila caerulea) Magee Marsh Wildlife Area, Ottawa Co., OH. 4/26/2009 © Darlene Friedman (Click to view a comparison of Atlas I to II) In early May, travelers along southern species is likely under- represented. This bird has one of the smallest effective survey Michigan rivers are sure to see banks lined with detection areas for a Michigan passerine as a the rich rose hue of Redbud flowers as well as result of its relatively high weak voice, the Blue-gray Gnatcatcher. It is these riparian unremarkable coloration, and diminutive size. sites where this tiny, sleek, long-tailed gray and The challenge of surveying for this species is white bundle of energy is most common in compounded by the fact that many birders lose Michigan. The gnatcatcher is uncommon in the the upper limits of their auditory range as they NLP and rare in the UP. The frequent thin nasal age. Consequently, gnatcatchers can be missed call notes or less often the delightful song, a by birders relying only on sound. rolling series of thin wheezy notes interrupted by high chips (Sibley 2000), are usually the first This species occurs in a wide range of wooded indication of this summer resident. Once the habitat in Michigan including deciduous forest sound source has been located, there may be ranging from dry to wet and young secondary two small birds in close proximity, calling back forest to mature forest, especially at forest edges and forth while in constant motion looking for and openings (Adams 1991). Habitat surveys in food or the best place to locate their tiny cup- MBBA I suggest that beech-maple, oak and shaped, lichen-covered nest. During the oak-hickory, elm-ash-red maple swamp, and summer, the Blue-gray Gnatcatcher can be silver maple-sycamore floodplain were found from southeastern Canada, northeastern commonly used forest types (Adams 1991). As U.S., and the Great Lakes west irregularly to the in the previous Atlas, areas of extensive Pacific Coast and then south to the Gulf Coast, farmland with small woodlots and heavily Mexico, and Central America. The northern populated human environments attract few limit of its range has expanded dramatically in gnatcatchers. The Blue-gray Gnatcatcher can recent years (Ellison 1992). also be found in pinion-juniper woodland elsewhere in its range, chaparral in the west, and Distribution in subtropical scrub, pine woodland, pine While the species map provides the approximate savanna and juniper scrub in Mexico and distribution of the Blue-gray Gnatcatcher in Central America (Ellison 1992). Michigan during the MBBA II period, this © 2010 Kalamazoo Nature Center Blue-gray Gnatcatcher (Polioptila caerulea) Breeding Biology This inquisitive bird can be found throughout The Blue-gray Gnatcatcher returns to Michigan the SLP. However, it occurs sporadically in on average from late April in the LP to early extensive farmland in the thumb and Saginaw May in the UP (Chartier and Ziarno 2004). In Bay watershed as well as Monroe and Lenawee recent years it has become common to find this Counties, and the urban settings in Wayne species before 20 April and it has been seen as County. A comparison between MBBA I and II early as 30 March. With the advance in spring reveals a trend of northwards range expansion. arrival, the nesting season has advanced A similar trend has been documented in similarly. Where Barrows (1912) wrote Wisconsin (Harriman 2006). In the NLP, the “nesting chiefly in late May and the first half of Blue-gray Gnatcatcher is now regular but June,” it is not uncommon today to observe nest uncommon north to the northern border of building in early May or even late April in the Mason County and east to the north end of SLP. Re-nesting and second broods extend Saginaw Bay with a few scattered records north nesting into the middle of July. Clutch size is to Leelanau and Alpena counties. Some of the typically three to five eggs which hatch in 13 expansion in the NLP appears to be following days, on average, with young fledging in about the Lake Michigan and Lake Huron shorelines. 13 days (Ellison 1992). Cowbird parasitism is Inland, expansion seems to be associated with noted frequently but varies widely over the lakefront and riparian habitat. In the UP, it gnatcatcher’s range. appears that the Blue-gray Gnatcatcher has been moving northward from Wisconsin into Abundance and Population Trends southern Menominee and Dickinson Counties. (Click to view trends from the BBS) There also was a single confirmed record in Population estimates for this gnatcatcher are Delta County. Elsewhere in the UP, the few 110,000 birds in Michigan with a continental records were scattered and with no Probable or population of almost 43,000,000 (PIF 2007). Confirmed breeding records noted. MBBA II surveys recorded 3,381 pairs. The percentage of townships in which this species At the beginning of the twentieth century, the was found increased in all three regions within Blue-gray Gnatcatcher’s range in Michigan the state between MBBA I and MBBA II, from centered on the three southern tiers of counties 21.1% of total townships to 28.6%. BBS (Barrows 1912), but by 1950 it was a summer population trend data from 1966 to 2007 show a resident ranging north to Huron and Newaygo statistically significant annual increase in Counties (Wood 1951). Northward expansion Michigan of about 4%, with mostly stable accelerated between the 1950s and the 1980s regional and national trends during the same when it had become uncommon in the UP and a period (Sauer et al. 2008). regular transient at Whitefish Point (Zimmerman and Van Tyne 1959, Payne 1983). Conservation Needs During the 1930s it had reached southeast The Blue-gray Gnatcatcher should benefit from Minnesota and in the 1940s it expanded in the global warming as Michigan is at the northern northeastern U.S. (Ellison 1992). The limit of its range and appropriate habitat is northward expansion of the breeding range in plentiful through the NLP and UP. While New York was associated with several protection of extensive tracts of forest is migratory over flights during the 1940s to the considered to be important for the gnatcatcher early 1970s (Bull 1974, Ellison 1992). (Robbins et al. 1989), recent thought suggests that microhabitat conditions may be a factor (Ellison 1992). Preservation of forest width © 2010 Kalamazoo Nature Center Blue-gray Gnatcatcher (Polioptila caerulea) along rivers and stream bottoms in the SLP is Robbins, C.S., D.K. Dawson , and B.A. Dowell. essential. As the continental population 1989. Habitat area requirements of breeding continues to increase, habitat on the wintering forest birds of the Middle Atlantic States. grounds could be an issue. Temperature can be Wildlife Monographs No. 103. an issue on the wintering grounds as breeding Sauer, J.R., J.E. Hines, and J. Fallon. 2008. bird census plot data and CBC results indicate The North American Breeding Bird Survey, noteworthy declines following severe winter Results and Analysis 1966-2007. Version weather in the 1970s (Ellison 1992). 5.15.2008. USGS Patuxent Wildlife Research Center. Laurel, MD. Literature Cited Sibley, D.A. 2000. The Sibley Guide to Birds. Alfred A. Knopf. New York, NY. Adams, Jr., R.J. 1991. Blue-gray Gnatcatcher. Wood, N.A. 1951. The Birds of Michigan. MP In Brewer, R, GA McPeek and RJ Adams Jr. 75. University of Michigan Museum of 1991. The Atlas of Breeding Birds of Zoology. Ann Arbor, MI. Michigan. Michigan State University Press. Zimmerman, D.A., and J. Van Tyne. 1959. A East Lansing, MI. Distributional Checklist of the Birds of Barrows, W.B. 1912. Michigan Bird Life. Michigan. OP 608. University of Michigan Special Bulletin. Michigan Agricultural Museum of Zoology. Ann Arbor, MI. College. Lansing, MI. Bull, J. 1974. Birds of New York State. Suggested Citation Doubleday / Natural History Press. Garden City, NY. Adams Jr., R.J. 2011. Blue-gray Gnatcatcher Chartier, A.T., and J. Ziarno. 2004. A Birder’s (Polioptila caerulea). In Chartier, A.T., J.J. Guide to Michigan. American Birding Baldy, and J.M. Brenneman (eds.). 2010- Association. Colorado Springs, CO. 2011. The Second Michigan Breeding Bird Ellison, WG. 1992. Blue-gray Gnatcatcher Atlas. Kalamazoo Nature Center. (Polioptila caerulea). In The Birds of North Kalamazoo, MI. Accessed online at: America, No. 23 (A. Poole and F. Gill, eds.) <www.mibirdatlas.org/Portals/12/MBA2010 The Birds of North America, Inc., /BGGNaccount.pdf >. Philadelphia, PA. Harriman, B.R. 2006. Blue-gray Gnatcatcher. In Cutright, N.J., B.R. Harriman, and R.W. Howe (eds.). 2006. Atlas of the Breeding Birds of Wisconsin. Wisconsin Society for Ornithology. Waukesha, Wisconsin, USA. Partners in Flight (PIF). 2007. PIF Landbird Population Estimates Database [web application]. Version 2004. Rocky Mountain Bird Observatory. <http://www.rmbo.org/pif_db/laped/default. aspx>. Payne, R.B. 1983. A Distributional Checklist of the Birds of Michigan. MP 164. University of Michigan Museum of Zoology. Ann Arbor, MI. © 2010 Kalamazoo Nature Center .
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