Effects of the Iron Baron oil spill on little penguins (Eudyptula minor). III. Breeding success of rehabilitated oiled birds

Abstract

The long-term effects of oiling on the breeding success of rehabilitated oiled little penguins (Eudyptula minor) were examined over two consecutive breeding seasons following the Iron Baron oil spill in 1995. The commencement of egg laying was delayed among rehabilitated oiled penguins compared with non-oiled birds during the 1995/96 breeding season. During that season, hatching success (number of eggs hatched from those laid) was no different in nests containing rehabilitated oiled penguins than in those containing non-oiled birds, but overall egg success (number of pre-fledging chicks from the number of eggs laid) was significantly lower among rehabilitated oiled birds. This effect was predominant in nests containing a rehabilitated oiled female, where the probability of successfully fledging any chicks was 22% lower than in nests containing a non-oiled female. During the 1996/97 breeding season, there was no significant difference between either the hatching or egg success of rehabilitated oiled penguins and non-oiled birds. In both seasons, the pre-fledging masses of chicks from rehabilitated oiled penguins were significantly lower than those from non-oiled birds. The chicks of rehabilitated oiled penguins were therefore expected to have lower survival than chicks raised by non-oiled parents. Results indicate that oiling not only reduced the number of chicks raised by rehabilitated oiled penguins in the short term, but also decreased the quality of young produced for at least two seasons following the spill.