Fiona,

I've been enjoying your great pictures of the Pied-billed Grebe nest at Green Lake.
Your final image of the youngster with a feather sticking out of it's bill is a nice documentation of the habit unique to grebes of eating feathers. This, to me, looks like a flank feather of an adult bird. The flanks are in a continual state of molt, specifically to provide feathers for ingestion. All grebes will eat their own feathers as well as some 'found feathers' (for instance when ducks are molting and many small feathers are floating around). Sometimes the very first 'meal' a newly hatched grebe chick receives is a feather the adult provides.

Feathers line the inside of grebe stomachs and also provide a 'plug' in the pyloric exit (stomach to small intestines). The feathers are thought to provide protection from sharp fish bones (adult grebes swallow fish whole and they slowly dissolve in the stomach acid, youngsters are proffered smaller pieces of fish but those may contain fish bones too), as well as a 'strainer' to keep the partially digested food inside the stomach long enough to dissolve.

A third theory postulates that the feathers provide bulk for pellets (grebes regurgitate pellets containing indigestible matter like chitin shields of insects they eat, or plant material ingested along with animal mater). The pellet is also thought to clean the esophagus of parasites as it works its way up and out (like the sponge that is sent through pipes, using water pressure, to clean the inside of the pipes at dairy farms, hence the name for the theory 'polishing sponge theory' -translated from the original Dutch 'poetsprop theory'-).

And all of that from a feather stuck to a chick's bill.

I hope you can keep the pictures coming.

Martin Muller, Seattle

----- Original Message -----
From: Fiona Cohen<mailto:fiona_cohen at yahoo.com>
To: tweeters at u.washington.edu<mailto:tweeters at u.washington.edu>
Sent: Wednesday, July 01, 2009 5:10 PM
Subject: [Tweeters] More pictures of Green Lake pied-billed grebe nest


There are still three babies and two eggs in the Green Lake pied-billed grebe nest. Here are some photos: http://naturegeeknw.blogspot.com/2009/07/still-three-baby-grebes-two-eggs.html<http://naturegeeknw.blogspot.com/2009/07/still-three-baby-grebes-two-eggs.html>