Welcome to the American Ornithological Society 2018 Annual Conference. We are pleased to have you join us at the lovely Hilton El Conquistador Resort in Tucson, AZ.
Studies of younger age classes are underrepresented compared to those on breeding birds, particularly for species with delayed maturation. For species such as Swainson's Hawks (Buteo swainsoni) this problem is further compounded by the inability to observe individuals before they begin breeding. Here we apply multi-state models in Program Mark to model pre-breeder dynamics. Specifically, we estimate annual cohort breeding recruitment probabilities (range 0.01-0.20) and first-year survival probabilities (range 0.07-0.31) from 1985-2014, a time period with significant population changes for Swainson's Hawks. For example, breeding surveys across the state of California estimated a 91\% decline in the number of breeding pairs in 1979, prompting a state listing-status of “threatened” in 1983. While multiple factors probably contributed to population declines, pesticide induced mass mortality events in the mid-1990s were documented across northern Argentina. Models that accounted for the permanent ban of pesticides responsible for mortality events in Argentina received the most support, suggesting that the disuse of this pesticide in 2000 was particularly important for this species. In addition, annual cohort recruitment rates notably increased after 2000. This result emphasizes the necessity and value of long-term monitoring and conservation work.
