The influence of diet-mediated exposure of avian influenza on adult survival, recruitment and territory occupancy in peregrine falcons.

The current outbreak of highly pathogenic avian influenza (HPAI) is the largest panzootic ever recorded, impacting millions of wild and domestic birds worldwide. Waterbirds including waterfowl, seabirds and shorebirds represent natural reservoirs for the virus and have facilitated its spread throughout major flyways. Peregrine falcons are obligate bird consumers and are considered HPAIV-susceptible. We investigated the influence of waterbird exposure on breeding peregrine falcons within the mid-Atlantic region of North America by comparing inland and coastal subpopulations. We monitored individually marked adults (N = 205) and breeding territories (N = 79) to estimate spatial and temporal patterns of adult survival, recruitment age and territory occupancy (2016-2025). Adult survival was comparable between inland and coastal locations prior to the arrival (date of first detection) of HPAIV but fell from 0.82 to 0.25 in coastal areas in the two years following arrival. Recruitment of juvenile-plumaged (second calendar year) birds was uncommon in both areas prior to the arrival of HPAIV but increased from 3.5% to 21.0% following arrival, suggesting that the recruitment pool may be diminished by the demand generated by increased adult turnover. Territory occupancy was high and stable prior to the arrival of HPAIV but declined by more than 50% in coastal areas following arrival. Our results document changes in adult survival, territory occupancy and juvenile recruitment that coincide with the appearance of HPAIV on the Atlantic Coast and suggest that impacts may be diet-mediated.