An investigation of the effect of inbreeding and management on reproductive success and survival in Chatham Island black robin (Petroica traversi)

Abstract

Pedigree and breeding performance data (n = 753 eggs laid) for the Chatham Island robin (Petroica traversi) were collected by the Department of Conservation during a 12 year recovery programme. This study used these data to examine the effects of inbreeding on survival and reproductive success. Effect of management on these traits was also considered because management strategies to enhance these traits to aid the programme were confounded with level of inbreeding. Analysis showed that management increased productivity of the population by enhancing egg production (managed = 5.07 eggs produced/pair/year, unmanaged = 3.65 eggs produced/pair/year). Chatham Island tits (P. macrocephala chathamensis) used as foster parents were slightly more successful at raising robin chicks to 1 year of age than black robin parents but a smaller percentage of tit-reared chicks were recruited into the breeding population. No apparent relationship between inbreeding and survival to various life stages was found. Age at death appeared to be weakly (negatively) correlated (-0.105) with inbreeding coefficient but this relationship was confounded with season of birth (which is positively correlated with inbreeding coefficient (0.362) and negatively correlated with age at death (-0.66). A weak correlation between eggs produced per year and inbreeding coefficient was attributed to management practices in early years and a predominance of younger birds (with higher breeding coefficients) in latter years. Overall, no clear effects of inbreeding on survival or reproduction were found. These results indicate that depressed performance is not necessarily the inevitable consequence of inbreeding.