Short-taiuled Shearwater Mortality

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Subject: Short-taiuled Shearwater Mortality
From: "Allan Morris" <>
Date: Thu, 26 Oct 2000 22:37:04 +1000
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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