Nesting of Red-Winged Blacbirds in Cattails and Commed Reed Grass in Mentor Harsh

During summer 1976, a study of habitat selection by the red-winged blackbird, Agelaius phoeniceus, was conducted. Mentor Marsh near Mentor, Ohio was chosen because of its unique geologic and botanical history. A swamp forest prior to 1959, the area is now a marsh composed of Typha latifolia, T. angustifolia, and Phragmites australis. Preferences of A. phoeniceus for each of these plants were investigated, and T. latifolia was significantly most chosen. Presumed advantages include rigidity, easy nest accessibility, and wide spacing to facilitate nest defense. Additional features of habitat selected such as available perches, proximity of open water, and edge effect were investigated. If rapid succession to monodominant stands of P. australis continues at the present rate, the nesting red-winged blackbird population may decrease sharply. OHIO J. SCI. 80(1): 14, 1980 During summer 1976, we attempted to determine if red-winged blackbirds (Agelaius phoenicus) chose a specific plant for nesting in Mentor Marsh. We also attempted to determine the advantages and disadvantages of nest construction in various plant types. Of additional interest was a prediction of future red-winged blackbird populations in the marsh, since succession was rapidly approaching a marsh composed of only common reed grass (Phragmites australis). Mentor Marsh is by no means an isolated environment, but due to its unique history of geologic formation and vegetation succession (Berstein 1977), a large area could be differentiated from surrounding available nesting habitat. Distinct patches of cattails (Typha latifolia and Typha angustiofilia) and Phragmites also could be distinguished within the marsh. STUDY AREA AND METHODS Located on the lake plains of north-central Lake County, Ohio, Mentor Marsh was originally an oxbow lake formed from the Grand River at some unknown time. A detailed account of the geologic and vegetational history of the marsh can be found in Bernstein (1977). Although the marsh was a swamp forest until 1959, a die-off of trees permitted replacement Manuscript received 13 October 1978 and in revised form 27 March 1979 (#78-60). Present address: Department of Ecology and Behavioral Biology, 108 Zoology, University of Minnesota, Minneapolis, MN 55455. of the swamp forest by marsh plants, mainly broad-leaved cattail (Typha latifolia) and narrow-leaved cattail (7". angustifolia). Common reed grass (Phragmites australis), uncommon in the initial marsh stage, has since proliferated and is now present and still spreading in tall monodominant stands covering 75% of the marsh. Three study areas were chosen. Study Area A (7 ha) was composed mainly of broad-leaved cattail, Studjr Area B (5 ha) contained mainly narrow-leaved cattail, and common reed grass was dominant in Study Area C (6 ha). Observations of red-winged blackbird populations began on 3 March 1976. Spring migrant survey continued until mid-June, nesting survey through August, and fall migrants were observed until November. The majority of observations were made within four hours after sunrise, but evening observations also were made. About 125 man hours were spent in territory mapping and searching for nests. A grid system of color and number coded aluminum pie pans at 20 m intervals within each study area facilitated territorial mapping and nest location. Observations were made from elevated land, trees, and an observation platform on the marsh border, and from within the marsh. Mapping techniques, as described by Svensson (1970), were used. Nests were assigned numbers and were labeled with small tags tied beneath them. Nest substrate, height above water or litter mat, dimensions and contents were recorded (table 1). Nest observations and/or territorial mapping were conducted every 3 to 4 days in each study area unless prevented by inclement weather. The time schedule of Meanlcy and Webb (1963), who suggested that females may abandon nests if stressed often, was followed. Each study area was censused an equal number of times at the same time of day.