RESPONSIVENESS OF NESTING NORTHERN GOSHAWKS TO TAPED BROADCASTS OF 3 CONSPECIFIC CALLS

Because locating nest sites of forest-dwelling raptors is difficult an d time-consuming, we determined if broadcasting conspecific vocalizati ons of northern goshawks (Accipiter gentilis; hereafter referred to as goshawks) increased goshawk detectability during the nesting season i n northcentral New Mexico (NM) and northcentral Arizona (AZ). We recor ded responses of goshawks to an observer who was either broadcasting a larm, wail, or juvenile begging calls, or was not broadcasting at all while walking transects. we sampled 215 transects at 27 goshawk nests during sampling periods associated with courtship, nestling, and fledg ling-dependency periods during 1990. Goshawk responses to taped conspe cific calls were higher (P = 0.02) than their responses to an observer without a tape. Detection rates were highest on transects with broadc asts during the nestling (73.3%) and fledgling-dependency periods (76. 9%). During all sampling periods, the probability of detecting a gosha wk was highest for observers broadcasting a conspecific vocalization w ithin 100-200 m of the nest. During the nestling period, the alarm cal l elicited the highest detection rate, whereas the wail and begging ca lls resulted in the highest detection rate during the fledgling-depend ency period. Vocal mimicry by Steller's jays (Cyanocitta stelleri; her eafter referred to as jays) (potential false positives) occurred on 16 .7% of the transects. The lowest mimicry rates occurred during the nes tling period. Our data suggest that goshawks are best surveyed with br oadcast conspecific vocalizations during brood rearing at stations tha t are 300 m apart on transects that are separated by 260 m, and that s tations on adjacent transects be offset by 130 m.