Tonya’s post about the dead ST Shearwaters in southern NSW, extends the grim picture that had been painted by my daughter who lives beside the beach at Peregian on the Sunshine Coast of Qld – by several hundred kilometres.
About the first week in November, she, and a young boy who happened to be walking on the beach, moved by compasssion rather than rationality, had been prompted to enter the surf to rescue a couple of floundering young shearwaters and took them to the Australian Wildlife Zoo – inevitably without a happy ending.
Apparently there were many dead shearwaters along the northern Sunshine Coast beaches and there had been even more a couple of weeks earlier. She is not sufficiently knowlegeable to have aged the dead birds she saw on the beach on those occasions, although the floundering birds were juveniles.
I join Tonya in an interest to hear explanations of the phenomena – the likely causes and whether juveniles are particularly at risk.
Angus Innes.
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I thank Mark and Graham for their informed comments. They expand my knowledge. But, like Tonya, there are still some questions that my land based birding mind is trying to come to grips with? As these birds take food from the sea and are happy swimming on a frequently lumpy ocean – what precisely causes the deaths? Do they attempt to fly through extreme wind conditions and perish through the exhaustion of food reserves, or is the wind speed so great that they cant handle either flying or swimming and become water logged and/or unable to feed – or is there some other factor, like no surface ocean food. Angus Innes
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Is it really that surprising that after a journey from the Bering Sea back to Australia that a few birds die? Wrecks of Short-tailed Shearwaters (STSW) and other seabirds occur regularly all over the world. In Australia, wrecks are common at this time of year because STSW adults returned at the end of September. Juvenile wrecks occur in April/May after they fledge. Some birds just aren’t going to make it. Given the breeding population is estimated to be between 23 -30 MILLION I don’t think the numbers that have been reported will have any significant impact on the population.
Wrecked birds can be very useful to science. Birds can be used in a number of different ways such as looking for effects of plastic ingestion, heavy metal contamination and staple isotope studies. Numbers and timing of wrecks can also be used to infer migration. Don’t forget, all birds should be checked for leg bands. STSW are the third most banded species in Australia (120,000 to date!).
Regards,
Mark
href=”mailto:angus.innes@environment-agency.gov.uk”>angus.innes@environment-agency.gov.uk href=”mailto:birding-aus@vicnet.net.au”>birding-aus@vicnet.net.au the Sunshine saw the privileged. If you have received this message by mistake, please notify the sender immediately, delete it and do not copy it to anyone else. should still check any attachment before opening it. to under the Freedom of Information Act, Data Protection Act or for litigation. Email messages and attachments sent to or from any Environment Agency address may also be accessed by someone other than the sender or recipient, for business purposes. terms and conditions which you can get by calling us on 08708 506 506. Find out more about the Environment Agency at http://www.environment-agency.gov.uk href=”mailto:birding-aus-request@vicnet.net.au”>birding-aus-request@vicnet.net.au
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Regarding whether it its really all that surprising to find a few dead shearwaters, given that their population is in the 10s of millions, I agree that it is not; but given that probably all of those birds weren’t passing through at once (if they do, that in itself is pretty amazing), and that the wreck here probably resulted in hundreds of thousands of dead birds, then I guess I do think it’s surprising. Perhaps not insidious or human-caused, but definitely remarkable; and potentially linked to climatic events like La Nina. I’m from the central coast of California, where there are regularly enormous rafts of 10s of thousands of birds very close to shore; yet I’ve never seen or heard described die-offs of this magnitude up there. It’s interesting, anyway!
Cheers,
Tonya
Hi all,
Just did a quick calculation: Population 23,000,000 Average lifespan 15-19 years say 17 Deaths per annum 1,352,941 Deaths per day 3,706 KIlometres of coast passed 500 kms per day Deaths per km of coast per day 7.4134 Assume 50% get washed in 3.71 per km of coast per day Duration on the beach 7 days Number of dead birds on the beach 25.95 per km = 1 every 40m or so
So during migration one should expect 1 dead STSW per 40m of beach.
During the breeding season around Tasmania and Bass Strait, one would expect occasionally huge numbers to wash up together in Tasmania, Victoria or South Australia.
Population dynamics is a numbers game.
Cheers,
Graham Buchan
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Is it really that surprising that after a journey from the Bering Sea back to Australia that a few birds die? Wrecks of Short-tailed Shearwaters (STSW) and other seabirds occur regularly all over the world. In Australia, wrecks are common at this time of year because STSW adults returned at the end of September. Juvenile wrecks occur in April/May after they fledge. Some birds just aren’t going to make it. Given the breeding population is estimated to be between 23 -30 MILLION I don’t think the numbers that have been reported will have any significant impact on the population.
Wrecked birds can be very useful to science. Birds can be used in a number of different ways such as looking for effects of plastic ingestion, heavy metal contamination and staple isotope studies. Numbers and timing of wrecks can also be used to infer migration. Don’t forget, all birds should be checked for leg bands. STSW are the third most banded species in Australia (120,000 to date!).
Regards,
Mark
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