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Length of Stay, Survival, and Habitat Use of Fall Migrant Sora (Porzana carolina) on the Patuxent River Marsh as Determined by Radio Telemetry

Michael Haramis, USGS Patuxent Wildlife Research Center, Laurel, Maryland 20708-4015

Greg Kearns, Maryland-National Capital Park and Planning Commission, Patuxent River Park, Upper Marlboro, Maryland 20772


The historic importance of the Patuxent River wild rice marshes to migrant sora (Porzana carolina), the decline in number of soras, and the paucity of information about the species prompted the Maryland-National Capital Park and Planning Commission to initiate study of the sora within the Park in 1987. These field investigations, led by naturalist Greg Kearns, have become a highlight of the Park program and grown each year to come to the forefront of research with the species. Past work has focused on developing effective capture techniques, developing age and sex criteria, and establishing baseline census techniques to document distribution, abundance and habitat preference. Success with techniques to capture soras is especially noteworthy. Improvements in call-enhanced walkin traps have contributed 1400+ bandings of soras, a figure that has more than doubled total bandings for the species in North America.

Participation of the Patuxent Wildlife Research Center (PWRC) has been solicited to lead new studies on soras based on past successes with the intent to formalize research efforts with accompanying peer review and product expectation. The present study is a collaborative venture between the Patuxent River Park and PWRC with anticipated financial support from the Fish and Wildlife Service's Webless Migratory Game Bird Research Program (WMGBRP). Funding for 1996 did not materialize from the WMGBRP and the study is presently supported by the Park and private sources, primarily Quail Unlimited.

The primary objectives of the present study are to investigate movements, habitat use, survival, and length of stay of soras at this exceptional migratory stopover habitat using radio telemetry methods. Secondary objectives include continued data collection on body mass, fat score, recapture frequency, and age-sex criteria based on large sample captures. The first field season has just begun and our first radio marked birds have been released for study.

The fresh-tidal Patuxent River wildrice marshes near Jug Bay, Upper Marlboro, Maryland, are an exceptional stop-over habitat for thousands of fall migrant Sora rails.

Waterside view of flowering wildrice at high tide, August 1992.

Sora venturing from vegetative cover at low tide to feed on wildrice grains on bordering mud flat.

Closeup view of an adult Sora rail.

A call-enhanced walkin trap powered by battery/solar panel unit. Use of microchip recordings of Sora and Virginia rail calls to attract rails to the traps have increased capture success to 700 plus rails during a short 2-month fall season.

Greg Kearns banding a Sora rail shortly after capture on the Patuxent wildrice marsh.

Bill and tarsus measurements are critical to determing sex and age of Sora rails.