Posted by: Anne Murray | October 4, 2010

Counting shorebirds

Long-billed Dowitchers at Reifel Bird Sanctuary, Delta, BC

Fall is a great time for shorebird watching around the Fraser delta.  On a recent visit to Reifel Bird Sanctuary at high tide our birding group was rewarded with impressive close-up views of hundreds of Long-billed Dowitchers.  They were feeding so intensely that they didn’t startle on our approach or even when a lively bunch of elementary school children arrived.

I was interested in estimating the number, which I guessed originally as being several thousand. However, I knew that estimations can be wildly off if one is inexperienced, so I decided to work it out more systematically.  I took some photos from up the viewing tower and printed them out. Then I circled each bird as I tallied them up, to make sure I only counted them once.  The birds were all standing slightly apart as they fed, so there was surprisingly little overlap.  It was a very still, calm day, so each bird cast a shadow, giving the appearance of twice as many birds. Off in the distance more birds spread out and these could only be roughly counted.

The big flock of Long-billed Dowitchers from above

My tally came to 591 birds in the large foreground flock with perhaps another 100 off in the distance, for a grand total of about 700 birds – not the thousands I had guessed, but a large number of dowitchers.

We looked at the birds carefully through binoculars and a telescope, and their plumages ranged from adult to juveniles.  They called quietly to each other as they fed.  As far as I could tell they were all Long-billeds, though of course you cannot tell by the length of bill.  I checked out the plumage variations in Sibley’s field guide and that, and the call notes, helped distinguish them.

A young Peregrine Falcon came down and harassed them repeatedly but failed to catch one.  The dowitchers flew up once, but quickly settled again – they must have been extremely hungry and were taking advantage of the good tidal conditions in the lagoon.

Anne Murray

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Responses

  1. Russ Cannings visited Reifel the day after us and he reported on BCVANBIRDS seeing 3000 Dowitchers there. At least I think thay’s the number he reported. A long time ago I was taught how to use a grid system to count large flocks, but I got old, and I forget the method. Cheers: Tom

  2. That is certainly the best way! My guestimate of 3000 was based on counting the birds in a small area – then projecting a”grid” in my mind and counting the grids then multiplying by the grid number – then adding the extra ones further down.


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