Habitat selection in a reintroduced population: social effects differ between natal and post‐release dispersal

Abstract

Understanding the factors driving dispersal behaviour and habitat selection in reintroduced populations can be critical to reintroduction success. Social factors in particular can influence habitat selection, for example through conspecific attraction, and this can have both positive and negative effects on reintroduction success, particularly where multiple releases occur. In addition, little is known about how habitat selection differs between natal and post-release dispersal within species. Often it is assumed that information from a species' natal dispersal preferences and patterns can act as a guide for predicting post-release dispersal behaviour, but no studies to date have examined this. We examine the factors influencing habitat selection during both natal and post-release dispersal in a reintroduced hihi (stitchbird, Notiomystis cincta) population using species distribution models. We demonstrate a strong social effect in habitat selection of natal dispersers bred at the release area (largely the offspring of founders), yet find no social effect in habitat selection of juveniles translocated 2 years after the first releases occurred. In addition, we establish that environmental variables are important in habitat selection in both groups. We suggest (1) that consideration of social effects and conspecific attraction should play a role in planning reintroduction release strategies, especially if reinforcement releases are considered necessary, and (2) that it may not always be appropriate to assume post-release dispersal in reintroduced populations will be driven by the same factors that influence natal dispersal.

Post‐release effects on reintroduced populations of hihi

“…Studies on rats have shown sex‐related differences in physiological response to the same stressors, resulting in differential changes in social, foraging, or anti‐predator behavior (Faraday , Teixeira et al ). The apparent sex‐linked difference in survival could also be due to females dispersing from Bushy Park; females at other sites have tended to show both greater natal dispersal (Richardson et al ) and more pronounced initial post‐release dispersal (Richardson ). However, radio‐tracking during the first month, a time when hihi could be expected to move extensively, indicated that they did not disperse beyond the forest boundary.…”

Effect of supplementary feeding on reproductive success of hihi (stitchbird, Notiomystis cincta) at a mature forest reintroduction site

“…The surrounding landscape is dominated by dairy pasture, offering little to no habitat for native species, essentially making Maungatautari an island. The construction of a 47 km Xcluder TM pest-proof fence around the reserve has allowed for the eradication of all introduced mammals, except for mice (Mus musculus), and low numbers of rabbits (Oryctolagus cuniculus) and hares (Lepus europaeus) (Richardson & Ewen 2016). Six supplementary feeders (20% sugar water solution) are provided for hihi, all within 150 m of the release site ( Fig.…”

“…This location also facilitates the regular maintenance of the supplementary feeders by staff and volunteers. Species distribution modelling has shown that hihi at Maungatautari tend to select breeding territories in close proximity to streams, and the majority of nests are located in pukatea (Richardson & Ewen 2016) regardless of whether nesting close or far from feeders. Given the similarity in habitat selection for all hihi at Maungatautari we assume little difference between feeder and non-feeder user territories.…”

“…To maximise genetic diversity, birds were sourced from both Hauturu (20) and Tiritiri Matangi Island (135). By 2012/13, there were 68 banded hihi in the population, and seven known unbanded hihi (see Richardson & Ewen 2016 for details of monitoring at the site). None of the unbanded hihi were known to use supplementary feeders.…”

“…This difference is probably due to young females establishing territories further from feeders and being unfamiliar with them. Territory locations were known from a concurrent study (Richardson & Ewen 2016). The 17 selected territories were closely monitored in order to determine nest initiation dates (usually by back-counting once incubation/hatching was confirmed) and to obtain an accurate count of the number of young fledged by each female over the breeding season.…”