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Wednesday, April 4, 2012

Spring diving

Along with the loon yesterday, we saw this species swimming and diving among the docks at Spud Point:

Horned Grebes (Podiceps auritus) are one of six species of grebes found near Bodega Head during the winter.  You may be more familiar with the non-breeding plumage dominated by dark gray and white.  This individual is molting into breeding plumage (there's a good illustration of this transitional plumage in the National Geographic Field Guide to Birds of North America, 6th edition).

This is a relatively small grebe (31-38 cm long), with a short, straight, thick pale-tipped bill (especially compared to Eared Grebes).  Note the red eye with a silver ring around the pupil.

The genus, Podiceps, means "rear foot", and probably refers to the position of the legs/feet so far back on the body.  If you look closely in the first two pictures, you can just make out the lobed feet under water.

As with loons, grebes are excellent foot-propelled divers.  Sometimes grebes start with a "springing dive" (see next photo).  Here's a good description:

"The head is arched upward slightly, then forward and downward accompanied by a strong thrust of the hind limbs, causing the forepart of the body to spring entirely clear of the surface and reenter the water more than twelve inches forward of the original position."  From Lawrence, G.E.  1950.  The diving and feeding activity of the Western Grebe on the breeding grounds.  Condor 52:3-16.

1 comment:

Claudia said...

The question has finally been decided. I always wondered if the feet were actually out of the water before the head entered.

I'm also amazed that there is so little splashing going on in that photo. The caption could read,

"Horned Grebe uses surface tension to create bridge with body"