2.1.12 Case study - Using tracking technology to locate endangered ‘ua’u (Hawaiian Petrel) burrows

The ‘ua’u (Hawaiian Petrel) is an endangered Procellarid 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, tracking devices were used to track breeding adults back to their burrows. Transiting birds heading to unknown breeding colonies were caught over the course of two years (2018 and 2019) using a spotlight (Grandlumen 240W High Bay LED UFO shop Light) and powerful hand held flashlights, combined with speakers playing ‘ua’u calls. In total six birds were caught, and a data logger (e-obs Bird Solar 10g) was attached to each bird via back sutures. Four base stations were then deployed on likely transit routes – these base stations allow for automatic data download from the tag to the base station whenever a bird came in range of the station.46

Data were downloaded from four of six (66.7%) birds, but complete tracks were only recovered for two (33.3%) birds (#6507 and #7238). A total of 23,627 locational fixes were downloaded from tagged birds, with 1773 (7.5%) locational fixes recorded over land. 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 ‘ua’u 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 the tracking data.

 Figure 62. Maps showing overland tracking data and eventual location of the ‘ua’u that was located by this technique.