Green Heron (Butorides virescens) Damon McCormick
Otter Creek, Benzie County, Michigan. 8/17/2006 © Alice Van Zoeren This species sponsored by Quentin & Barbara Schultze. (Click to view a comparison of Atlas I to II)
Although adorned in a gaudy pastiche of forest, Possible MBBA I records from the NLP and UP may have represented dispersed birds from slate, rufous and cream, the Green Heron’s downstate or elsewhere. preference for thickly-vegetated wetlands renders it a relatively uncommon sight in Breeding Biology Michigan. It is about one-third the size of its Green Herons feed both day and night in a more conspicuous relative, the Great Blue variety of wetland environments, hunting small Heron, with a comparatively shorter neck and fish, invertebrates and insects in shallow water legs and an altogether stockier build. with dense vegetation (Meyerreicks 1962,
Recher et al. 1983, McNeil et al. 1993, Davis Distribution and Kushlan 1994). One of the few tool-using In addition to most of Central America, Green birds, they will often drop feathers, mayflies and Herons breed throughout the eastern half of the other small objects onto the water’s surface in United States and along its west coast; Michigan an effort to lure fish (Keenan 1981). Audubon represents the northern limit of their range (1843) observed that “During the love-season (Davis and Kushlan 1994). Although noted on they exhibit many curious gestures, erecting all Isle Royale in Kneeland’s 1859 survey, Barrows the feathers of their neck, swelling their throat, (1912) and other early naturalists reported the and uttering a rough guttural note like ‘qua species to be prevalent in the SLP and rare qua’, several times repeated by the male as he elsewhere in Michigan, perhaps due to a struts before the female.” Of an intermediately preference for deciduous wetland shrubs and social nature, Green Herons can nest both trees over their coniferous counterparts (Peck solitarily and, less frequently, in loose colonial and James 1983). Nonetheless, Kelley (1975) aggregations (Kaiser and Reid 1987). Breeding speculated that Green Herons occurred regularly pairs will jointly construct a nest of small twigs, in the UP, and Chu (1991) concluded that typically above water in swamp or marsh MBBA I data probably reflected “a real increase thicket, and concealed by overhead branches in the number of individuals summering in the (Reed 1927, Meyerreicks 1962, Davis and northern part of the state.” However, because Kushlan 1994). Both parents incubate three to Green Herons tend to wander widely after five eggs for approximately 20 days; hatched breeding (Kushlan 1981), some of the numerous downy young are semialtricial, and can fly
© 2010 Kalamazoo Nature Center Green Heron (Butorides virescens) Damon McCormick within four weeks (Meyerreicks 1962, Gavino – has been replaced with a suite of legislative and Dickerman 1972). Although two clutches measures that frequently call for the creation or have been documented in more southerly restoration of habitat in compensation for the regions, Michigan pairs likely nest only once loss of other wetland acres (Michigan per season (Davis and Kushlan 1994). Department of Natural Resources 2007). Because some evidence suggests that these Abundance and Population Trends mitigative efforts often result in compensatory (Click to view trends from the BBS) wetlands of lower quality than the original As during MBBA I, the majority of MBBA II acreage, and because wetland integrity has been block-level records for Green Herons occurred shown to correlate with species richness in the in the SLP (73% in MBBA I; 70% in MBBA Great Lakes region, it is possible that II), with clusters of relatively high densities in Michigan’s Green Heron population is suffering the southwest counties of Kalamazoo and Van under the state’s current protection scheme Buren, and the southeast counties of Wayne and (Steiner 2003, Stapanian et al. 2004). As such, Washtenaw. Total abundances between Atlas survey efforts designed to identify associations efforts dropped sharply: Confirmed and between specific wetland types and Green Probable blocks fell 35% and 57%, respectively, Heron breeding occupancy and productivity while township-level numbers experienced within them would likely provide a clearer comparable declines. These figures stand in picture of the species’ statewide conservation contrast with the findings of the Marsh needs. Monitoring Program, which determined no significant population trend for the species Literature Cited across the entire Great Lakes region from 1995- 2006 (Harrison et al. 2008) and with the recent Audubon, J.J. 1840. Birds of America. conclusion of the Wisconsin BBA that Green [Internet] Green Heron. http://www. Herons are “doing well” in this neighboring audubon.org/bird/BoA/F38_G1e.html state (Gostomski 2006). However, both studies (accessed 12 May 2009). – as well as BBA accounts for Ohio and Illinois Barrows, W.B. 1912. Michigan Bird Life. – stress the difficulty in accurately censusing a Special Bulletin. Michigan Agricultural species whose secluded habitats and College. Lansing, MI. predominantly solitary nature render it Chu, P.C. 1991. Green-backed Heron unrecorded on most BBS routes and excluded (Butorides striatus). In Brewer, R., G.A. from most surveys of colonially nesting waders McPeek, and R.J. Adams Jr. (eds.). The (Peterjohn and Rice 1991, Kleen et al. 2004). Atlas of Breeding Birds of Michigan. Although these considerations also weigh upon Michigan State University Press, East the reliability of MBBA trend data, the Lansing, MI. magnitude of the decline in breeding Green Davis, W.E. Jr., and J.A. Kushlan. 1994. Green Heron records between Atlas efforts suggests Heron (Butorides virescens). In The Birds some measure of actual retraction within of North America, No. 129 (A. Poole and F. Michigan over the past fifteen years. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA. Conservation Needs Gavino, T.G., and R.W. Dickerman. 1972. The unregulated agricultural drainage and Nesting development of Green Herons at commercial development of state swamps, San Blas, Nayarit, Mexico. Condor 74: 72- marshes and bogs – which by one estimate 79. eliminated over 72% of Michigan’s 11 million wetland acres during the 19th and 20th centuries
© 2010 Kalamazoo Nature Center Green Heron (Butorides virescens) Damon McCormick
Gostomski, T. 2006. Green Heron (Butorides
© 2010 Kalamazoo Nature Center