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Breeding biology and feeding ecology of little penguins Eudyptula minor at Phillip Island – a basis for a monitoring program

Chiaradia, A (1999) Breeding biology and feeding ecology of little penguins Eudyptula minor at Phillip Island – a basis for a monitoring program. PhD thesis, University of Tasmania.

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Abstract

This research examined the breeding performance of little penguins (Eudyptula minor)
at Phillip Island in south east Australia. A major goal was to relate breeding success to
fluctuations in food availability within and between seasons. Data was collected on nest
attendance patterns, pair bonding, chick growth rates, chick meal mass, adult time
budget and diet. Sampling extended over two reproductive seasons, one with good and
other with poor reproductive success.
Implanted identification transponders combined with an automated penguin monitoring
system were used to determine daily nest attendance. Successful breeders had shorter
incubation shifts and undertook more foraging trips than failed breeders during both
incubation and chick guard periods. The later a little penguin started to breed the poorer
was its breeding performance.
Males guarded their partners throughout the pre-egg periods but left their females as
soon as the first egg was laid. Observations of the penguin pairs in their burrows
showed that they had different partners on 33% of the recorded occasions. This was
used as an indication of extra-pair copulation during the pre-egg period. Changing
partners and burrows between seasons decreased reproductive success. Inter-seasonal
divorce rate was 28%, one of the highest amongst penguins, even though evidence
suggests that divorce behaviour has no obvious benefit for little penguins.
During chick rearing, four fish species comprised 93% of the penguins’ diet. These
species were red cod Pseudophycis bachus, barracouta Thyrsites atun, warehou
Seriolella brama and anchovy Engraulis australis. Mean meal mass decreased as the
breeding season progressed while foraging trip duration increased. Birds kept the
length of their foraging trips below two days during the good season. During the bad
season birds foraged longer than two days right from the beginning of the post guard.
Compared with successful breeders from the bad season, successful breeders from the
good season guarded their chicks for 6 days longer, had a post-guard that was 9 days
shorter and their chicks grew faster.
Little penguins exhibited substantial temporal and seasonal variation in their time
budget and foraging performance. The variation was used to identify whether
differences in breeding performance and food availability were related to natural causes
or to commercial fishing activities. As the stock biomass is unknown for most of the
commercial fishery in Victorian waters, it is difficult to prove the existence of
detrimental effects of fishery on the food supply for the penguins. There was evidence,
however, that fishery may impact on the penguin foraging performance. The little
penguins from Phillip Island consumed almost the same amount of fish as was caught
by commercial fisheries in Victoria. Pilchards and anchovies have decreased
dramatically in importance in the penguin diet while the commercial catches of these
fish have increased progressively. This suggests that there might be competition
between penguin feeding and commercial fishing.

Item Type: Thesis (PhD)
Keywords: seabirds, diet, automated systems, mating system, chick growth, attendance patterns
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Date Deposited: 29 May 2012 23:28
Last Modified: 11 Mar 2016 05:54
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