Captive breeding for reintroduction: influence of management practices and biological factors on survival of captive kaki (black stilt)

Abstract

An important component of the restoration strategy for the critically endangered kaki or black stilt (Himantopus novaezelandiae) is captive breeding for release. Since 1981 1,879 eggs were collected from wild and captive pairs, with birds laying up to four clutches. Eggs were incubated artificially and most chicks reared by hand until released as juveniles (about 60 days) or sub-adults (9-10 months). Because survival in captivity is a significant determinant of the number of birds available for release, we wished to identify sources of variation in mortality to assess potential impacts of management on productivity. Hatchability was 78% for captive-laid eggs and 91% for wild-laid eggs. Survival of hatched eggs was 82% by 10 months of age for both wild and captive birds. Most egg mortality occurred early in incubation and around hatching: the timing of mortality was unaffected by whether birds were captive or wild, hybrid or pure kaki, or when eggs were laid. Heavier hatchlings showed higher initial survival, as did chicks from wild parents. Hatchlings from fourth-laid eggs showed lowest survival, even though hatchling mass tended to increase with hatch order. Survival of chicks subjected to major health interventions was 69% after 4 months. No differences in survival were found between different genders, hybrids and pure kaki, handreared or parent-reared birds, chicks hatching early or late in the season, different seasons, different-sized groups of chicks, chicks reared in different brooders, juveniles kept in different aviaries, and chicks from subsequent clutches. Birds subjected to minor health interventions were equally likely to survive as healthy

Genetic analyses reveal hybridization but no hybrid swarm in one of the world’s rarest birds

“…Using hatching success, fledging success and survival to reproductive age as fitness proxies, we found evidence of significantly reduced hybrid fitness in dark hybrid female × male kakī pairs (Table 1). The reduced fitness of hybrid females only may explain the failure of a previous study, which did not separate male and female hybrid offspring or include individual differences as a random effect, to detect reduced fitness (van Heezik et al. 2005).…”

“…Initiated in 1981, the Kakī Recovery Programme includes a captive‐rearing programme: in general, eggs collected from captive and wild pairs are incubated in captivity, chicks are then brooded and reared in captivity, and juveniles or sub‐adults are subsequently released to the wild (van Heezik et al. 2005).…”

“…Data on reproductive success of kakī × light hybrid and kakī × poaka pairs were not available. For details regarding the captive‐rearing programme see van Heezik et al. (2005).…”

Conservation genetic management of a critically endangered New Zealand endemic bird: minimizing inbreeding in the Black Stilt Himantopus novaezelandiae

“…We used hatching success (measured as the proportion of eggs laid per pair that successfully hatched) as a measure of reproductive success. Because eggs were artificially incubated in standard conditions, hatching failure is directly related to intrinsic rather than extrinsic causes of failure (van Heezik et al. 2005).…”

Captive breeding and rearing of critically endangered Mauritius fodies Foudia rubra for reintroduction

“…Criticisms of captive breeding programs include claims that it deflects attention and resources away from more urgent conservation problems such as habitat preservation and restoration [Rahbek, 1993;Snyder et al, 1996]. However, captive breeding programs in the country of origin have been successful in providing individuals for release [van Heezik et al, 2005;Tweed et al, 2003], and Butchart et al [2006] recently reported that captive breeding or reintroduction has been used in onethird of all programs that have recently saved a bird species from extinction.…”