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Tuesday, May 1, 2012

A short migration? Knot.

Along with many other shorebirds, a large flock of Red Knots (Calidris canutus) was feeding and resting along the shoreline of Bodega Harbor last night.

Most of the Red Knots were in (or well on their way to being in) breeding plumage.  Note the red breasts/bellies and beautifully patterned back feathers (dark centers with pale fringes and rust-colored spots).  The relatively short bill and short legs are also helpful field marks.  (There are 8 knots in the first photo, and 11 knots in the second.)

I was focused on the Ruff at the time (see yesterday's post), so unfortunately didn't get a good Red Knot count.  The picture below has the most individuals captured in one view.  This might be tricky — you'll need to avoid counting a few smaller/darker brown dowitchers — but I'll let you count before revealing the number (my count is below the image).

In the photo above, I counted 33 Red Knots.  (This is a high number for Bodega Harbor.)

A few Red Knots were still in basic or non-breeding plumage.  These birds look dramatically different than those in breeding plumage.  They are primarily gray above and white below (see next photo).  Although the colors are very different, notice how the overall shape and proportions are the same.

Several of the Red Knots were banded — see the bird in the lower right corner of the next photo.  It appears to have a white flag on one leg.  Flag colors indicate where the birds were banded.  If I'm interpreting information on the Internet correctly, a white flag means this bird was banded in Canada.

Red Knots are long-distance migrants and undergo some of the most remarkable migrations of any animal.  Some of them breed in the high Arctic and spend the winter in Tierra del Fuego in Argentina — a one-way trip of 15,000 km!

Recent studies have shown that they make several physiological adjustments before starting these long-distance flights.  They change their metabolic rate, organ sizes (decrease stomach and gizzard), muscle masses (decrease leg muscle, increase flight muscle), and fat mass (increase fat).  After doing so they can undertake non-stop flights of up to several thousand kilometers at one time.

No wonder they need to rest every now and then.



Claudia said...

No wonder they're all sleeping. The importance of a quiet environment (without dogs and people) for these birds makes so much sense within the context of their long flights. Basically, Bodega Harbor needs to be one of the best birds B&Bs around.

cricket said...

Wow ... Amazing physiological changes ... for the migration ... All these wonderful miraculous feathered friends we have around us !