Some aspects of the ecology of the fairy penguin Eudyptula minor novaehollandiae (Forster) in southern Tasmania
Hodgson, A (1975) Some aspects of the ecology of the fairy penguin Eudyptula minor novaehollandiae (Forster) in southern Tasmania. PhD thesis, University of Tasmania.
Observations of the fairy penguin commenced in 1958 and are
continuing intermittently at three sites in Southern Tasmania. Graphs
and tables of weights were useful in interpreting the behaviour of
breeding birds. Departure weights of fledglings were used as criteria
for breeding success. Birds were sexed by cloacal examination, confirmed
by dissection when possible. Provisional sexing by accurate measurements
and comparisons of bill depths proved 97% reliable with adults and was
applied to fledglings.
Between 1959 and 1963 at the intensive study area on the Neck
connecting North and South Bruny Island, a surplus of females, not evident
among fledglings, adversely affected the breeding of many birds.
Juveniles displayed, kept company and occupied nests without breeding.
Two- and three-year-old birds bred unsuccessfully. Young birds not
banded as fledglings were detected by bill size or growth and
irregularities in behaviour causing breeding failure. Recoveries from
Victoria, Cape Barren Island and South Australia of birds banded as
fledglings or suspected juveniles, included one which had bred
unsuccessfully seven years earlier on Bruny Island. Four males and
eleven females, returning here when over ten years old, included two
females which were established breeders thirteen years earlier and
therefore aged at least sixteen years.
From May t o July the few birds that came ashore collected
nesting material, displayed and copulated promiscuously, often in the
open. From August onwards displays increased in intensity prior to
egg-laying, both sexes participating in fighting and nests being
occupied by successive pairs with frequent exchanges of partners. Eggs
were laid from September to December and daily observations were essential
to determine the birds responsible. Clutches of two eggs were produced
within 45 to 96 hours. Most eggs laid late in the season and all second
clutches were unsuccessful. No second clutch was produced following
Successful parents alternated in incubating eggs for 31 .5 to
38.5 days and in guarding chicks for a further 16 to 28 days, then
combined to feed them regularly until they departed. Chick mortality was
high at 77%. Males delivered more food, but deserted more readily.
Feathering necessitated abundant food, shortage causing immediate
retardation. The critical period was after banding, when chicks were
over 5 to 6 weeks old. Rare cases of adoption of a young chick and
feeding of alien fledglings were recorded.
Onset of breeding and moulting were correlated. Irrespective
of condition, moulting could not be unduly delayed. The process took 15
to 20 days. Breeding pairs often moulted together.
Small groups of separate east and west populations occupied
different localities on the east and west sides of the Neck study area,
with some overlapping and a few east-west matings. The total population
gradually declined, due to natural losses, mainly from the pod-chick to
the pre-egg period and losses of breeding and non-breeding birds
attributable to human agency. The resulting disturbances affected
breeding in subsequent seasons and few young west side birds became
established, so that by 1972 the west population was nearly non-existent.
|Item Type:||Thesis (PhD)|
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|Keywords:||fairy penguin, Bruny Island, Chick mortality, southern Tasmania, Eudyptula minor novaehollandiae |
|Deposited By:||UTAS ePrints Officer [HE]|
|Deposited On:||11 Nov 2008 10:01|
|Last Modified:||17 Sep 2012 12:34|
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