Updated avifauna of Mokuʻaeʻae Rock Islet 2019

Abstract

Mokuʻaeʻae Rock Islet, located off the North shore of Kauaʻi is protected as a Hawaiʿi State Seabird Sanctuary. In the late 1970s it was also the site of a cross-fostering project for the endangered Newell’s Shearwater Puffinus newelli. Few avifauna surveys have been undertaken on the islet, with the most recent prior to this report being undertaken by the Kauaʿi Endangered Seabird Recovery Project (KESRP) in 2013 and 2015 respectively. For this study, the islet was surveyed in June and October of both 2018 and 2019. Burrow searches were conducted across the entire islet to obtain breeding population estimates for each species and to assess whether there was any recent sign of Newell’s Shearwater breeding activity. Two Song Meters (Wildlife Acoustics, SM2+) were also deployed each year at the same two locations, with data collected for two months in June and July. Auditory surveys were also conducted in June 2018 for two hours after sunset and one and a half hours before sunrise. A total of 17 bird species was recorded over the course of the two years, consisting of eight seabird species (of which three – Bulwer’s Petrel Bulweria bulwerii, Wedge-tailed Shearwater Ardenna pacifica and Red-tailed Tropicbird Phaethon rubricauda - were confirmed breeding), one native waterfowl species (Nene Branta sandvicensis, which is the first confirmed breeding record on the islet for this species), five migratory species, and three introduced species. As with previous searches of the islet, there was no sign of Newell’s Shearwater breeding activity and only a handful of calls recorded, concurring with previous reports that the cross-fostering project on the islet was not successful. Despite this, the islet remains an important sanctuary for the three seabird species recorded as breeding on the islet during the surveys and remains the only known breeding colony of Bulwer’s Petrel on Kauaˈi. Depredation by the introduced Barn Owl Tyto alba was identified as a significant threat to seabirds breeding on the islet. Future management actions are suggested to improve the islet for breeding seabirds.