Eastern Screech-Owl (Megascops asio) Thomas Carpenter
Bay County, MI © Joe Soehnel (View Comparison of Atlas I & II)
Unique among Michigan owls because of its The ecological tension zone between the two color morphs (red and gray), the Eastern southern oak-hickory/beech-maple forest and Screech-Owl is a ubiquitous denizen of the the northern mixed coniferous forest also small woodlots that typify the southern LP. As characterizes the northern boundary (Shea implied by its name, it occurs east of the Rocky 2006). Mountains north to southeast Saskatchewan, west central Montana and the southern borders Differences in distribution between MBBA I of Quebec and Manitoba (Adam 1987). The and MBBA II were minor. More townships had southern portion of its range extends into confirmed breeding during MBBA I. MBBA II northeast Mexico, and from west Texas east to established more records for Sanilac County and the Atlantic Ocean (Gehlbach 1995). In documented possible or probable breeding Michigan, Eastern Screech-Owls are common in status in three counties without records during the southern LP and uncommon in the northern MBBA I (Alpena, Oscoda and Muskegon). In LP. the southern LP, both atlases show a preponderance of records in the southeast and Distribution southwest. These differences probably reflect Prior to European settlement, Eastern Screech- variations in coverage rather than an actual Owls were likely uncommon. As settlers change in distribution. Confirmed breeding was cleared away the forest, the owls apparently documented north to Montmorency and Antrim flourished. They were considered abundant by Counties, with probable breeding in Emmet the beginning of the 20th century (Barrows County during MBBA I. The northernmost 1912) and likely peaked in numbers soon confirmed breeding was in Grand Traverse thereafter (Carpenter 1991, Peterjohn and Rice County, with possible records north to 1991). MBBA I and MBBA II found Eastern Montmorency and Alpena Counties, during Screech-Owls to be widespread in the southern MBBA II. Thus, the northern extent of LP, with a few records in the northern LP and distribution during MBBA II is slightly south of no confirmed records for the UP. The absence that shown by MBBA I. Whether this is real or from the UP is not surprising; the species an artifact of differences in coverage cannot be reaches the edge of its range in the northern LP, readily ascertained, but the northern boundary where winter temperatures and snow depth may fluctuate in response to winter weather apparently limit it. conditions (Shea 2006).
© 2011 Kalamazoo Nature Center Eastern Screech-Owl (Megascops asio) Thomas Carpenter
Abundance and Population Trends Both atlases probably underestimated the true Eastern Screech-Owls were recorded in 34% of distribution, especially in the southern LP where townships in the southern LP and five percent in Eastern Screech-Owls likely inhabit most the northern LP during MBBA II, with townships. The most effective way to locate confirmed breeding in 23 and three townships, Eastern Screech-Owls is through nocturnal respectively. No obvious changes in abundance playback of their calls during winter. are evident between the two atlases, and the Townships without records were probably not population appears to be stable. The Breeding censused via this technique. Bird Survey does not effectively detect this species, which does not even appear as a Eastern Screech-Owls occupy a variety of selection choice in the trend section of its habitats including urban and rural woodlots, website. Confirmation of breeding is quite parks, cemeteries, residential areas with mature difficult unless birds are utilizing nest boxes, as deciduous trees, marshes, and riparian areas. In natural nesting cavities are difficult to locate. areas with extensive timber, they are usually Breeding is most readily confirmed by detecting confined to the edge rather than the forest fledged young responding to playback during interior (Peterjohn and Rice 1991). The major the summer months. requirement for breeding is apparently the presence of mature trees with suitable nesting Extremely severe winters cause temporary cavities; birds can be enticed into areas with reductions in population (Carpenter 1991), younger trees via nest boxes (Gehlbach 1995). which usually rebound within a few years once more normal conditions return (Peterjohn and Breeding Biology Rice 1991). Competition with fox squirrels for Eastern Screech-Owls have an 18 week nesting cavities is common, and may limit breeding cycle (Gehlbach 1995). Egg laying breeding opportunities, particularly in urban and commences from mid March to mid April in the suburban areas (DeCandido 2005). Nestlings southern LP (Craighead and Craighead 1956, are susceptible to predation by raccoons. Peterjohn and Rice 1991), and probably begins Vehicular collisions cause a number of earliest in urban and suburban locations fatalities, with dispersing young and males (Gehlbach 1995). Young fledge during May provisioning broods apparently most at risk and June and are dependent on their parents for (Gehlbach 1995). Predation by larger owls, eight to ten weeks thereafter (Gehlbach 1995). particularly Great Horned Owls, is also a Once independent, young disperse to new significant source of mortality. Rodenticides locales, usually less than 32 km (20 mi) from can inflict mortality in both rural (Hedgal and their place of birth (Van Camp and Henny 1975, Colvin 1988) and urban (Stone et al. 2003) Gehlbach 1995). However, this may not hold environments, but their impact does not appear true at the northern edge of the range, where to be significant. The spread of the West Nile significant post-breeding dispersal is purported virus into Michigan probably had the most to occur (Shea 2006). Once post-natal dispersal impact on raptors since MBBA I and may have is completed, Eastern Screech-Owls are caused some mortality in Eastern Screech-Owls considered non-migratory (Gehlbach 1995). (Komar 1996, Nemeth et al. 2006), but some However, Shea (2006) states that there is some evidence suggests its effects were minimal southward migration at the northern edge of the (Gancz et al. 2004). The long-term impact of range. urbanization is equivocal. There is no evidence that Eastern Screech-Owls have disappeared from urban parks in Michigan, but it has
© 2011 Kalamazoo Nature Center Eastern Screech-Owl (Megascops asio) Thomas Carpenter happened in New York City (DeCandido 2005), York City, 1987-2005. Urban Habitats 3:1- and the long-term viability of urban populations 20. needs more study. Gancz. A.Y., I.K. Barker, R Lindsay, A. Dibernardo, K. McKeever, and B. Hunter. Conservation Needs 2004. West Nile virus outbreak in North The Eastern Screech-Owl does not require any American Owls, Ontario, 2002. Emerging special conservation needs and is not on any Infectious Diseases. watch lists. Nest box programs could increase
© 2011 Kalamazoo Nature Center Eastern Screech-Owl (Megascops asio) Thomas Carpenter
1998-2001. Bulletin of Environmental Contamination and Toxicology 70:34-40. Van Camp, L.F. and C.J. Henny. 1975. The Screech-Owl: its life history and population ecology in northern Ohio. North American Fauna No. 71. U.S. Fish & Wildlife Service, Washington, D.C.
© 2011 Kalamazoo Nature Center