More than you ever wanted to know…

about fecal sacs!

On two different occasions, lately, Katherine as said, “Hey, did that bird have a fecal sac?”

“A what?”

“A fecal sac. You know. When the parent takes out the feces of the baby bird. It keeps the nest clean.”

I had never heard of a fecal sac and so I ignored her. 😉

However, recently we visited Elkhorn Slough Reserve and saw a Downy Woodpecker go into its cavity nest with some food. It left shortly thereafter with something in its beak.

“Was that a fecal sac?” Katherine asked.

I chimped* my camera to see if my photo showed this hypothetical fecal sac.

*to chimp is to immediately look at your camera to view the picture you just took. It is often accompanied by “ooh, ooh, aah, aah” — hence the name.

I saw a blurry photo (the plant in the foreground was nicely focused) of the woodpecker poking its head out of the cavity. I could tell, though, that it had something in its beak.

We continued to watch the nesting site for several minutes. The next time we saw a parent with food, it brought the food to the cavity and poked its head in. However, the parent quickly took its head out again without feeding any babies.


“I think the parent is trying to encourage the babies to fledge,” she said. “It’s saying, ‘Yummy food out here! Come and get it!” We had seen this kind of action with the Northern Mockingbird and its babies in our yard before they fledged and it made sense.

We continued to watch as the parent proffered the food six more times before finally relenting and flying into the cavity to feed a baby.

When we got home, I looked up “fecal sac.” Katherine was right! This is what Wikepedia has to say (summarized and combined with my own observations):

A fecal sac is a mucous membrane that surrounds the feces of some birds — mostly passerines — before they have fledged. While some birds will pretty quickly learn to poop over the nest, others (altricial young…see this post for a brief mention of altricial and precocial) who remain in the nest for longer periods, generate fecal sacs.

Some parents remove the sacs — as this woodpecker did. Others….

…eat them. 😛

(I’m surprised that when I did research on bird poop (see this post), I never read about fecal sacs.)

Downy Woodpecker about to go into the cavity nest with food.
Downy Woodpecker poking its head out of the nest after feeding young…no fecal sac present
Downy Woodpecker encouraging its young to come out and get this tasty green bug. In the space of six minutes, the parent offered the food seven times before going into the nest and feeding
Downy Woodpecker leaving nesting cavity with fecal sac

So, what have I learned from all this?

Listen to Katherine!

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