We quantified the frequency of alarm calls given by nesting pairs of gray hawks (Buteo plagiatus) along the San Pedro River and Huachuca Mountains of southeastern Arizona during the breeding season of 2016. Parental investment varies among bird species, but for some hawk species investment increases throughout the breeding season. For that reason, we predicted that the gray hawk’s frequency of calls would increase from incubation to fledging. We used six remote microphones to record the alarm calls, and they were cycled every three days among 12 nests. We randomly selected nests from categories based on proximity to nearest neighboring nest. Using the recordings, we counted the number of calls in one hour increments. We chose to look at the hour of 7:00-8:00 in the morning, because gray hawks are the most active in the morning. We spaced out analyzation throughout the nesting period, taking 12 counts in total through incubation (-10 days from the hatching date) to fledging (42 days after the hatching date).
Results/Conclusions
Preliminary findings show average calls among nests ranged from 0.5 calls/hr when chicks were 30-34 days of age to 35.8 calls/hr when chicks were 0-4 days of age. There was wide variation in frequency calls among nests, and no clear trend through the nestling period. Our findings did not support our prediction, however there are potential reasons for this preliminary result. One factor that may have influenced call frequency and contributed to the high variation was proximity to human activity. Nests closest to human activity appeared to have higher call frequency than those further away.