| Popis: |
Crested penguins (genus Eudyptes ) have a remarkable brood reduction system in which the first of two eggs laid is much smaller than the second and frequently disappears from the nest. The causes of this mortality are uncertain. In royal penguins, E. schlegeli , 70 of 84 pairs lost their first egg during the 4-day interval before the second was laid, and in 15 of 22 observed losses, mothers actively ejected their own eggs from the nest. Most first-egg losses (57%) occurred within a day prior to the appearance of the second egg. Parental ejection in royal penguins was not associated with high rates of extra-pair parentage: DNA fingerprinting of 13 two-chick families detected only one individual that was unrelated to its putative father. A manipulation experiment, intended to assess the viability and insurance value of first eggs, yielded equivocal results. The hatching success of first eggs, which were temporarily removed and then substituted for second eggs, was only half that of second eggs that were not removed (48% versus 93%, N =89), but apparent viability differences due to egg type may have been confounded by delayed incubation and additional handling. None the less, the apparent reproductive value of first eggs was low; only one of 137 unmanipulated first eggs hatched. Some testable hypotheses are suggested for the evolution of ejection behaviour in Eudyptes . |
Full Text from ScienceDirect