Trudy A. Chatwin
British Columbia Ministry of Environment, Lands and Parks, 2080 Labieux Road, Nanaimo, B.C. V9T 6J9
Abstract: I collected data on the timing of vocalizations by Common Poorwills at two Okanagan Valley sites during six June 1995 nights to determine whether or not call rates during the twilight period differed from those during the post-twilight period. My results showed that poorwills called more frequently after twilight, in contrast with previous findings in California and locally of greatest vocal activity by this species during crepuscular periods. Detection of poorwill calls decreased significantly when winds were above 6.4 km. per hour (strong breeze). From these findings, I suggest that inventory protocol for Common Poorwills should include recommendations that surveys begin one-half hour before the darkest part of the night (Nautical Twilight) and that surveys not be conducted on windy nights.
Key words: Common Poorwill, diurnal vocalization patterns, inventory protocol, Okanagan Valley, Phalaenoptilus nuttallii, wind effects
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