Factors affecting post-release dispersal, mortality, and territory settlement of endangered kokako translocated from two distinct song neighborhoods

Abstract

Animal translocation success rate is generally low, with the causes of failure poorly understood without comprehensive and protracted monitoring. Here we examine the outcome of a translocation of endangered North Island kokako (Callaeas wilsoni) from two adjacent song neighborhoods in New Zealand, each with individual vocal traditions (c. 75% of phrases unshared) to a single release site. We conducted detailed radio-telemetry to monitor post-release dispersal over 50days during four serial releases of 20 birds while we broadcast neighborhood-specific song around the release site. The birds moved substantial distances after release, however overall short-term release site dispersal was not as great as predicted by a random walk model, suggesting an attraction to playback and/or a reluctance to explore areas away from the release site. This apparent attraction was not specific to a given song neighborhood, however. Although the post-release mortality rate (22% over 31days) was relatively high in this translocation, we did not detect an effect of sex, age, source origin, or duration of captivity on mortality. We show that habitat use during this acclimation period was disproportionate to availability – the birds’ preferred habitat was similar to that at the capture site. At least four pairs formed, with two and three confirmed breeding in the first and second seasons post-release respectively. Mate choice was non-assortative with respect to song neighborhood, revealing that reduced phrase sharing rates found in adjoining neighborhoods are not a barrier to pair formation. We compare this example with other kokako translocations and make recommendations for future translocations.