Using Tracking Technology to Locate Endangered ʻuaʻu or Hawaiian Petrel (pterodroma Sandwichensis) Burrows

The `ua`u, or Hawaiian Petrel, Pterodroma sandwichensis, is an endangered seabird endemic to the Hawaiian Islands. Although its distribution on some of the islands is well documented, on larger islands such as Hawai`i there are significant distribution gaps. Previous work within the Pu`u O `Umi Natural Area Reserve (NAR) on Hawai`i strongly suggested that a breeding colony of the species was present, but active burrows had not been located making it difficult to focus management actions. Searching for burrows of this nocturnal burrow-nesting seabird had been particularly challenging in the NAR, as the birds are very rare, widely dispersed, and breeding in remote areas with dense vegetation and challenging topography. To locate active burrows, we employed the use of tracking devices to track breeding adults back to their burrows. Six data loggers (e-obs Bird Solar 10g) were attached to transiting birds caught using lights in 2018 and 2019. Overland locational data was then interrogated for concentrated areas of circling and ground activity. This resulted in several areas of concentrated activity and two different locations where tracked birds ended up transmitting from the ground. Burrow searching teams were then deployed to these areas and an active Hawaiian Petrel burrow was located. This represents the first active burrow ever documented in the NAR and the entirety of Kohala Mountain. Management actions have since been initiated to protect birds breeding within the areas defined by our tracking data. Logistical and methodological considerations inherent in the use of telemetry for locating endangered seabird colonies are discussed.