Bald Eagle Nest Monitoring

Non-target species in SGin Xaana Sdiihltl’lxa (Night Birds Returning) Gwaii Haanas National Park Reserve, National Marine Conservation Area Reserve and Haida Heritage Site

Abstract

Data on bald eagle (Haliaeetus leucocephalus) nests in or near Juan Perez Sound in Gwaii Haanas National Park Reserve, National Marine Conservation Area Reserve and Haida Heritage Site dates back to 1998. The purpose of this paper is to report on the status of the database, conduct a preliminary analysis of existing data relevant to the SGin Xaana Sdiihltl’lxa (Night Birds Returning) project, and look for supporting evidence that changes in seabird populations may impact the bald eagle population in Gwaii Haanas. Since 2010, nests have been monitored on small islands as part of the non-target species monitoring program for the SGin Xaana Sdiihltl’lxa seabird restoration project. Introduced rats that predate seabirds are decimating seabird colonies on islands in Gwaii Haanas. To restore nesting habitat, the project involves the removal of rats from small islands using a toxic bait. The bait poses a secondary and tertiary poisoning risk to eagles foraging carcasses. The data collected on occupancy, activity and reproductive success of bald eagle nests suggest tremendous nesting success for eagles occurs on islands with seabird colonies and without rats compared to islands with rats on them. Of the total number of nests surveyed in 1999, 2011, 2012 and 2013, eagle nests on islands with seabird colonies showed the highest overall reproductive success, followed by islands without rats. Islands with rats had notably lower reproductive rates. Other studies demonstrate eagle predation of birds as a significant food source and emphasize the importance of food sources to eagle reproductive rates. The results presented in this report suggest that seabirds are a food source contributing to bald eagle reproductive success in Gwaii Haanas. Prey remains data for eagles nests from 2011, 2012 and 2013 were observed as an indication that eagles predate seabirds, but did reveal any notable results.