Post‐translocation assortative pairing and social implications for the conservation of an endangered songbird

Abstract

Animals translocated for conservation purposes may be sourced from multiple locations which may exhibit inter-site variability in reproductive behaviours. The influence that these differences may have on the propensity of pair formation, and the ultimate impact this may have on the success of the translocation, is unknown due to the low sample sizes of many translocations. We address this knowledge gap by collating an existing 18-year data set documenting multisource translocations of the endangered North Island Kō kako, Callaeas wilsoni, a duetting New Zealand species with known population-specific vocalizations. We found a strong, statistically significant tendency for Kō kako to pair assortatively with respect to source population (like with like) following release. Populationspecific differences in sexually selected behaviours that are important in mate choice decisions, such as bird song, are likely the proximate explanation for such reproductive decisions. Accounting for the tendency to pair assortatively following translocation may be particularly important when managing highly vocal animals like Kō kako that produce vocal duets and cooperatively defend territories as mated pairs. Consequently, careful consideration of behavioural variation between translocated individuals should be made, which will appropriately inform decisions relating to release-cohort composition. Failure to consider such variation may negatively impact the success of a translocation as the effective population size of the founder group may be lower than intended. Our findings make an important contribution towards understanding the impact that behavioural variation can have on the conservation of endangered species, and highlight the value of combining long-term data from multiple sources.

The uses and implications of avian vocalizations for conservation planning

“…This has been reported following multiple conservation interventions in the North Island Kokako ( Callaeas wilsoni ) (Bradley et al. 2014).…”

“…Very few mixed‐dialect pairs formed (Bradley et al. 2014), and mixed‐dialect pairs took considerably longer to form than matched pairs (Rowe & Bell 2007). The long‐term impact of mate selection based on dialect is not clear.…”

“…2002) and evidence from translocations (Rowe & Bell 2007; Bradley et al. 2014). We speculate that if reintroduced birds are unable to breed with wild populations or to persist as stable populations themselves and if reintroduced birds compete with native populations, then competition created by reintroductions may hasten rather than prevent extinctions.…”

Demographic influences of translocated individuals on a resident population of house sparrows

“…Reproductive skew caused by assortative mating has previously been found in translocation studies, e.g. related to male body mass (Sigg et al ) and male song affected by source of origin (Bradley et al ). The low success for translocated males to mate with resident females (and partly also translocated females with resident males) limited the intermixing of the translocated individuals into the local population (Fig 2).…”

“…In translocations, such differences may result from assortative mating, e.g. where individuals pair assort with respect to origin (Bradley et al ). Assortative mating could cause increased variation in mating success, where the total population may suffer a decrease in effective population size (Wright , Anthony and Blumstein , Bradley et al ) and may have consequences for demographic variance and viability of small populations (Lande , Lee et al ).…”