Effects of inbreeding and parental incubation on captive breeding success in Hawaiian crows

Abstract

Inbreeding can reduce individual or population fitness and is predicted to have particularly severe effects on early life traits. Detecting inbreeding depression remains a challenge, however, especially in endangered species or long-lived taxa. Ample and detailed data are needed to study the effects of inbreeding at various life stages. We used 17years of captive breeding records of the Hawaiian crow (Corvus hawaiiensis) to study the effects of individual and parental level of inbreeding on survival through early life. Using pedigree data to calculate inbreeding coefficients for over 300 eggs, we find that the individual’s inbreeding coefficient, but not the parents’, has a very strong effect on embryo and chick survival. Inbreeding levels of chicks that survived to 2years (reproductive age) are 31% lower than those of embryos and chicks that died. Highly inbred embryos have a>5 times reduced survival probability as a consequence of individuals carrying on average 6.9 haploid lethal equivalents for survival to 2years. Further, offspring survival is greatly improved by longer parental incubation. Individuals surviving to 2years had, on average, twice as many days of parental incubation prior to artificial incubation (four vs. two). Our study contributes to evidence that the strength of inbreeding depression is particularly severe in early life traits. It shows that the negative effects of inbreeding on reproductive success should be accounted for even in benign captive environments where survival is maximized and suggests that parental incubation should be favored over artificial incubation in avian captive breeding programs.