Are Dawn Vocalization Surveys Effective for Monitoring Goshawk Nest-Area Occupancy?

Abstract

In 1999 and 2000, we used dawn vocalization surveys (Penteriani 1999) to confirm nest-area occupancy by northern goshawks (Accipiter gentilis atricapillus) breeding in montane forests of northeastern Utah, USA. We visited 19-20 historic nest areas in 1999 (n = 20) and 2000 (n = 19; 15 were sampled both years) during the courtship period (mid-Mar through late Apr), and recorded the type and duration of calls heard. We detected vocalizations at 51% of the nest areas surveyed with this technique (45% in 1999 and 58% in 2000). Overall accuracy rate (nest areas in which we correctly determined occupancy status) was 90%. On average, goshawks vocalized over a 62-min period at dawn, but durations ranged from 3 to 117 min. We found dawn vocalization surveys to be an effective technique to determine the status of known goshawk nest areas during the courtship/pre-incubation periods, although the technique requires considerable effort when applied to remote, montane forest locations. With only minor modifications to the Penteriani (1999) protocol, the technique can be easily adapted to monitor status of known goshawk nest areas in any area where local knowledge of nesting chronology is available.