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Turdus migratorius
These robins were busy feeding their brood and cleaning the nest. A fecal sac is a mucous membrane, generally white or clear with a dark end, that surrounds the feces of some species of nestling birds. It allows parent birds to more easily remove fecal material from the nest. The nestling usually produces a fecal sac within seconds of being fed; if not, a waiting adult may prod around the youngster's cloaca to stimulate excretion. Removal of fecal material helps to improve nest sanitation, which in turn helps to increase the likelihood that nestlings will remain healthy. It also helps to reduce the chance that predators will see it or smell it and thereby find the nest. There is evidence that parent birds of some species gain a nutritional benefit from eating the fecal sacs; studies have shown that females — which tend to be more nutritionally stressed than their mates — are far more likely to consume sacs than are males.
Seen in a neighbor's yard.
5 Comments
Thanks, Karen and Marta. I have seen bluebirds carry the sacs away instead of eating them, too.
Wow! thanks for sharing! I did not know about this :-)
Great spot Maria! I see the bluebirds cleaning their nests - they fly some distance with the fecal sacs presumably so they don't attract predators to the nest.
You're welcome. I only learned about them a few years ago when I saw a bluebird leaving its nest with these and I had to find out what they were.
Interesting information-we didn't know about fecal sacs. Thanks for sharing! And great series!