The impact of highly pathogenic avian influenza (HPAI) on Cape Breton Island’s bald eagle (Haliaeetus ieucocephalus) population

Abstract

In 2022 Nova Scotia was subjected to a widespread outbreak of highly pathogenic avian influenza (HPAI) virus. The eastern region of the province experienced extreme numbers of infected Northern Gannets washing up along the coastlines of Cape Breton Island. The outbreak occurred during the Bald Eagle breeding season, late May into early June, in Cape Breton. HPAI is spread through ingestion or contact with bodily tissues and fluids, posing a risk for species that scavenge on carcasses. Bald Eagles are carrion feeders and favour easily accessible and ample food sources. Bald Eagles foraged on diseased carcasses of Northern Gannets during the spring and summer of 2022, raising concern for the impact HPAI would have on the Island’s eagle population. This study aimed to (1) determine if nesting activity was lower across the Bald Eagle population of Cape Breton Island in the breeding season following a significant HPAI outbreak and (2) determine if Bald Eagle nests with a foraging range that overlapped with marine coastline had lower rates of active nests when compared to nests where foraging ranges did not overlap. Overall there was a lower number of active Bald Eagle nests across Cape Breton Island in 2023 when compared to 2022. There was no significant correlation between foraging range overlapping with Northern Gannet carcass availability and nest status. This research has the potential to inform management decisions surrounding Bald Eagles in Nova Scotia and provides a baseline evaluation of the regional Bald Eagle population response following a major disease outbreak.