Effects of the Iron Baron oil spill on little penguins (Eudyptula minor). II. Post-release survival of rehabilitated oiled birds

Abstract

The post-release survival of rehabilitated oiled little penguins (Eudyptula minor) was monitored over 20 months following the Iron Baron oil spill (10 July 1995) in northern Tasmania, Australia. During rehabilitation, over 1800 little penguins were individually banded and detailed records kept of factors including their degree of oiling, sex, capture and release mass and capture and release condition. Post-release survival of rehabilitated oiled little penguins was assessed through regular trapping of birds over two breeding sites (Ninth Island and Low Head). The minimum estimate of post-release survival was 59% for penguins from Ninth Island and 44% for penguins from Low Head. Rehabilitated oiled little penguins had significantly lower survival than non-oiled birds at both sites. The main factor affecting post-release survival was the extent of oiling, which itself had a significant influence on the capture mass and condition of birds. Combined, these factors had the greatest power to predict post-release survival. Other factors that significantly affected post-release survival included release mass and condition, and the sex of the bird. The duration of rehabilitation and whether birds were translocated (200–410 km) from their capture site prior to release did not significantly affect survival. The results of this study indicate how aspects of oiling, the condition of birds and rehabilitation affect post-release survival. As such, they will help improve the success of wildlife rehabilitation in future spills, and highlight the importance of individually marking rehabilitated oiled wildlife and post-release monitoring in assessing the success of rehabilitation programs.