What's in the bill?

When I arrived home from work, I stepped out of the car to see a White-breasted Nuthatch (Sitta carolinensis) on a tree next to our house.  We don't see them in our yard that often, so I picked up my camera to take a picture.  I only took a few before it flew off.  When I downloaded the images, I was a little surprised by this one:

 

You can see that the nuthatch is holding something in its bill.  This generates a lot of questions.  What is it?  And how is it being used?  Can you think of a few different possibilities?

Here are some options that I wondered about:

Option 1 — It could be food.  In this case, I'm not so sure.  It doesn't look quite right for a caterpillar or a beetle, for example.  And it looks too large for a seed.

Option 2 —  It could be a tool.  Other species of nuthatches (Brown-headed Nuthatches and Pygmy Nuthatches) are known to use pieces of bark and twigs as tools to probe for food.  I don't know if this has been documented in White-breasted Nuthatches, but it's an intriguing possibility.

Option 3 — It could be an object used to conceal food.  Both Brown-headed Nuthatches and White-breasted Nuthatches have been observed to use a piece of bark to hide seeds.

Did you think of other options?

Unfortunately, I didn't see what the nuthatch did with the object in its bill, so it remains a mystery.  But it's something to watch for in future encounters with nuthatches. 

ADDENDUM [20 March 2013]: Option 4 — You'll laugh, but this morning I woke up thinking, it could be a piece of bark that the nuthatch had removed while searching for food.  Not as exciting as the other options above, but I can't discount it.

Pygmy Nuthatches are more common in our yard (see below).  They're much smaller than White-breasted Nuthatches, e.g., 4.25" long vs. 5.75" long.  And notice how the gray on the head comes down to the eyes, giving the face a much darker appearance.  They also have a slight buffy wash on the breast.

 

 

For more information about Pygmy Nuthatches, review the post from 12 March 2012.