Studies of the Acadian Flycatcher in Michigan

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Abstract
Empldonax flycatchers, including E. virescens, were studied. This sp. occurs northward to central lower Michigan during the breeding season, reaching Oceana, .Montcalm, and Saginaw counties. The birds were observed in 3 different woods, 1 in Muskegon, 2 in Calhoun counties. On the 3 study areas 12 adult males were banded, 8 returned the year after banding; 5 the 2nd year; 2 the 3rd year; 1 the 4th year. Females, 19 were banded, 6 returned the 2nd year; 5 the 3rd; 4 the 4th. In all but one case pairs returned to their same mate and territory each succeeding year. Territory sizes in Muskegon County averaged 3.07 (1.8-4.2) acres; in Convis Township, 2.76 (2.1-3.8) acres, and in Emmett Township, 2.92 (2.1-4.2) acres. Trees used for nest sites in Muskegon County were hemlock (61.11%), maple (3.7%), and beech (31.48%). The most common trees in 10 m quadrate there were Acer saccharum, Tsuga canadensis and Fagus grandifolia. The height of 138 nests averaged 405.5 cm. above ground ranging from 107 up to 1,676 cm, always built out on a long sweeping branch at least 24.4 to 558 (average, 326.6) cm from the tree trunk. The average measurements of 106 eggs were 18.64 X 13.99 mm and the average weight, 1.85 g. The nesting season lasted from late May or early June until mid or late Aug. Most pairs attempted to raise 2 broods. Incubation required 13 (1), 14 (8), or 15 (2) days and was performed only by the female, who incubated at one nest for 84.1% of the time during 196 minutes on 2 different days and for 91.13% for short periods on 3 different days. Both parents feed the young, which remain in the nest 13 to 15 days. Of 121 Acadian nests, 78 had young fledge in them (64.4%). Of 319 eggs, 216 (67.7%) hatched and 183 (57.37%) fledged. Cowbirds laid 27 eggs in 25 nests, 3 in 1 nest, 1 in each of the rest. These occurred in 1st nests only, and each cowbtrd that hatched was usually fatal to the Acadian eggs (which failed to hatch) or to the young (they starved to death) for the cowbird usually hatched prior to the Acadian eggs by as much as 3 days.

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