Status assessment of peregrine falcons in North America using integrated population models

Species status assessments require an understanding of underlying population dynamics and important drivers of species demography. Large-scale assessments can be difficult due to challenges collating data obtained through different methods and different sources at multiple scales. Integrated population models (IPMs) provide a unified framework to combine multiple data sources and jointly estimate population parameters over a large spatiotemporal scale. We developed separate IPMs to estimate abundance and demographic rates for a northern (NMP) and southern (SMP) management population of peregrine falcons (Falco peregrinus) in North America from 2008 through 2019 (SMP) and 2020 (NMP). An outbreak of highly pathogenic avian influenza (HPAI) starting in 2021 led us to extend our modeling effort to assess its impact on these management populations by updating both IPMs using index data of population size through 2024 in a predictive framework. Survival probabilities differed drastically between first-year and after-first-year individuals in both management populations. After-first-year survival was nearly identical between the NMP and SMP, but first-year survival was lower in the SMP. Mean productivity was significantly lower in the NMP compared to the SMP, whereas the probability of breeding was similar in both management populations. Estimated total abundance for the NMP was substantially larger than the SMP, representing most of the North American peregrine population. Population growth was positive for both management populations, albeit at a slower rate for the NMP. The NMP declined from 2017 to 2018 coinciding with a drop in 2018 estimated productivity. When we extended the IPMs with updated count data through 2024, the NMP slightly declined but estimated abundance remained above levels at the start of the time series analyzed. The SMP grew at a similar rate to that predicted during the period informed by demographic data. We did not detect a continental-scale change in population size or trajectory in either management population associated with the arrival of HPAI in 2021. Further monitoring can support determination of whether the declines in the NMP were temporary, can enhance understanding of the underlying mechanisms, and can be used to guide the conservation and management of the peregrine falcon population in North America.