Night surveys of Yellow Rails, Coturnicops noveboracensis, and Virginia Rails, Rallus limicola, in Alberta using call playbacks

Abstract

The Yellow Rail (Coturnicops noveboracensis) and Virginia Rail (Rallus limicola) are inconspicuous and apparently rare species in Alberta. Wide scale, targeted surveys have never been conducted for either species, and virtually nothing is known about their distribution, populations, or other traits in the province. We compiled historical records of Yellow and Virginia Rails and conducted nocturnal field surveys using call playback as a first step in clarifying the status of these species in the province. Sixty-two Yellow Rail and 66 Virginia Rail historical sites were collated, with the majority of records occurring in the central and south-central parts of the province. A total of 431 surveys were conducted at 404 sites between 17 May and 6 July 2000. These sites included 69.4% and 60.6% of historical sites for Yellow and Virginia rails, respectively. We encountered 42 unique Yellow Rails and 59 unique Virginia Rails during the surveys, with only 7.0% and 17.5% of visited historical sites being occupied. Fifteen new sites for Yellow Rails were found. Most notable was the presence of 21 birds on Hay Lake in northwestern Alberta, which is a 450 km extension to the known breeding range. Twenty-three new sites for Virginia Rails were found. Playbacks were more effective at detecting Virginia Rails, as the number of spontaneously calling individuals was lower than was found for Yellow Rails (55.0% vs. 80.4%). Yellow Rails were most likely to be found in seasonal wetlands containing sedge, whereas Virginia Rails occupied a wide variety of semipermanent and permanent wetlands. Yellow Rails were most likely to be found when there was little or no moon, and during the middle (darkest) part of the night. Virginia Rails were found significantly more often when the moon was more than half full and relatively unobscured by clouds. The efficiency of future surveys for these species could therefore be improved by focusing efforts during periods and conditions when birds are most likely to be detected.