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Hi Birders,
I have read with interest the comments about
Shearwater mortality along our beaches during mid to late October, and some
birds are still coming ashore! Large wrecks of seabirds is a common
phenonomen particularly Short-tailed Shearwaters and Prions. However
when you have a number of years with low mortality, which we have had
since about 1995, when it does occur a new bunch of observers crops up who
have had no experience with such a situation and they immediately blame
pollution, oils spills etc for the cause of death, when basically it is
starvation.
Prior to the advent of seabird watching from
Sydney, Wollongong, Portland etc, us older birdwatchers could only record the
rarer seabirds by walking the beaches after big storms to see what seabirds were
washed up. In the 1960s I can remember huge wrecks of Prions in the
Sydney-Wollongong area, and well known observers like Keith Hindwood, Arnold
McGill, Doug Gibson & Allan Sefton would all be out walking the beaches and
bringing back their prizes to the Australian Museum for identication. My first
Slender-billed, Antarctic & Medium-billed Prions, Buller's Shearwater,
Flesh-footed Shearwater, Sooty Albatross, Arctic Jaeger & White-winged Black
Terns were all beachcast and I have yet to see a Sooty Albatross alive from one
of the Pelagic trips!
During 1970's for 7 years I helped organise the
recording and counting of dead seabirds along the beaches of NSW with Glenn
Holmes being the greatest contributor by far! For instance in 1974 about 20
contributors travelled 2441 km and found 7409 dead seabirds of 40 species,
giving a mean mortality of 3.0 birds per km of beach surveyed. There were 320
patrols totalling 717 km while Glenn Holmes used a motor cyle to travel the
remaining 1724 kms mostly within the Maclean, Coffs Harbour and Hastings Zone.
Of the 7409 dead seabirds, 6928 were Short-tailed Shearwaters, of which 1620
were found in October, 1898 in November & 2662 in December! These are not
small numbers! In one year the major Short-tailed wreck was in February, but
usually October to December was when most Short-tails came to grief. Similarly
in 1975, 1220 Prions of 4 species but mostly Fairy Prions were found dead
primarily in June & July, while between Sep 1974 & Feb 1975, 2440
Short-tails alone were found on the beaches of the Bherwerre Peninsulat (Jervis
Bay area). These figures are faily compatible with those found in NSW this
October!
The pattern of mortality was usually the same. The
non-breedering Short-tailed Shearwaters were moving south down the NSW coast
(the breeding adults usually move through in September, the non-breeders come
later) at a time when there were repeat south-west or southerly changes passing
through, which produce strong south or southeast winds that buffeted the NSW
coast. The Shearwaters, being temperate ocean feeders, would have used up all
their food resources in crossing the basically foodless for them, tropical
oceans, enroute back to Australia, only to arrive back in south-eastern
Australia to be greeted with some strong southerly-south east winds as they
attempt to move south to their breeding and feeding grounds. The birds are
exhausted and have to battle the strong onshore winds which push them against
the coast. (North-east winds and westerly winds would have pushed them out to
sea so that the birds would have only had to detour slighly and then move back
into their southerly pattern. Once starvation has set in, then they seem to make
no response to the efforts of wildlife carers to feed them and send them on
their way again.
I would have said that this latest mortality is the
highest that I have witnessed since about 1990 when there were some fairly
large wrecks. I counted 310 dead Short-tails and 1 Silver Gull in 2 kms of
Tuggerah beach near Pelican Point on 23 October, while 300 were removed
from Birdie Beach, Munmorah on 15 October, where there were 53 new specimens on
16 October within the same 2 kms. However we need to bear in mind that the
breeding population of Short-tails has been estimated at 23,000,000 birds (see
HANZAB), and bearing in mind that females don't breed until 4-5 yrears old and
males until 8 years of age, the non-breeding population could be of similar
proportions. While the mortality may reflect a failure of the local food supply
as well for these birds, the seabird literature gives plently of examples in the
past of similar wrecks of Shearwaters at this time of the year.
Alan Morris
Records Officer NSWFOC
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