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Beached shearwaters

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Subject: Beached shearwaters
From: Tim Reid <>
Date: Thu, 26 Oct 2000 22:05:49 +1100
Hi all,

Just a short comment on shearwaters (and a plug for more contributors to the Australian Seabird Group Beach Patrol Scheme!). Whatever has affected Short-tailed Shearwaters is not a local event (e.g. small hydrocarbon spills in St Kilda), as there are records of large numbers dying in much of eastern Australia and in New Zealand. What is also interesting is that whatever has happened has not effected any other species (except perhaps for early reports of Wedge-tailed Shearwaters in NSW), as in Tasmania and New Zealand apparently numbers recorded of other species (such as Sooty Shearwaters) are normal.

There have also been suggestions that this is just a normal event and nothing to worry about. Is this reasonable? In the last week in southern Tasmania we have surveyed 14 km and counted 665 Short-tailed Shearwaters (a rate of 47.5/km), while there are other reports of hundreds on other beaches (and large numbers floating dead in the channel). (From what I have read on birding-aus, this sounds typical of what other people are finding.) Fortunately, there is data in the Australian Seabird Group Beach Patrol scheme that can be compared with this result (see below). From this it would appear the rates birds are being encountered is very high compared to previous years. Nevertheless, the data for comparison is rather thin on the ground, so I would encourage anyone who feels the urge to help the ASG beach patrol scheme and have regular pleasant strolls on the beach. They should get in touch with me and I will help join them up.

Why are the birds dying? I don't know. But several I weighed were very light (about 400g c.f. 500-550g on return according to HANZAB). We have sent a collection off for post-mortems, but haven't got the results yet. Perhaps there was some problem with foraging in the Northern Hemisphere (La Nina? global warming? who knows?) this past winter in the areas that the Short-taileds were foraging in.

Hope this was of interest,

tim.


Below are the results for the Australian Seabird Group Beach Patrol scheme for three areas for the month of October:

Southern Tasmania
year    distance (km)   birds   rate (birds/km)
1993    14              20      1.43
1994    3               2       0.66
1995    5               5       1.00
1996    4               0       0.00
1997    4               0       0.00
1998    6               2       0.33
1999    25              20      0.80

Otways (Victoria)
year    distance (km)   birds   rate (birds/km)
1993    22              3       0.14
1994    21              117     5.57
1995    22              4       0.18
1996    25              25      1.00
1997    27              100     3.70
1998    2               0       0.00
1999    20              10      0.50

Northern New South Wales
year    distance (km)   birds   rate (birds/km)
1993    0                       
1994    99              576     5.82
1995    68              2       0.03
1996    12              7       0.58
1997    28              1       0.04
1998    34              3       0.09
1999                            


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