Mystery Pellet at Bird Feeder

Tom Gaynor, a White Memorial friend,
found this mysterious item at his bird feeder the other day.
Can you guess what it is and who left it?

Several bird species have a unique way of digesting their food.  When a bird swallows large objects or lots of food at one sitting the food needs to be processed in the crop, which is an organ that grinds the food into smaller parts.  Then the food enters the stomach, where digestive juices containing acids and enzymes break the food into smaller more useful pieces.  The portion of the food that is not as digestible and remains large gets pushed back up into an organ before the stomach that is also considered part of digestive system called the proventriculus.  The proventriculus compacts the indigestible pieces into a compact ball referred to as a pellet.  The pellet is regurgitated out the mouth and onto the ground.  Pellets are cool things because when we dissect the pellet we can learn what the animal has eaten.  For instance, owls and other birds of prey eat small mammals and birds.  By dissecting the pellet and identifying the skull, fur, and feathers in the pellet we can learn what species the bird ate but it also indicates what species can be found in the area where the bird hunts. Pretty cool!

Take a closer look at the pellet photographed above.  This pellet has small stones and vegetative material in it.  So, what bird would eat small stones and vegetation.  A pretty hungry one, you might think!  Some birds have adapted tough beaks to break open the seeds but other birds have not.  The stones aid in the crushing of food in the crop and some vegetation like tough seeds need a little bit more grinding to extract the food inside that tough seed coat.  Or sometimes these stones could also help break down even tougher food items like bones.  So, what are your clues so far - the bird is eating mostly vegetation and seeds, but does not have a tough enough bill to break open seeds like sunflower seeds so it needs to also eat small stones.

Let's look at the size of the pellet next.  This pellet measures about 3 centimeters long and about 1.5 cm wide.  So that would have be to a relatively larger bird to make a pellet that size.  So, not a house finch, sparrow, or goldfinch.  Probably not a Northern Cardinal either.  Any guesses yet, we've learned a lot so far...

This pellet is the calling card of an American Crow!  Crows have highly variable diet and can eat both vegetable and meat, which makes them an omnivore.  The stones help them break down the seeds and bones that they eat.  Take a closer look around your bird feeder next time to see what evidence you find to tell you what is visiting it.  Learning what you can there will help you figure things out when you observe something on your next venture into the woods.


Marlow said...

Wow! Now that's an amazing piece of out-put! Never would have thought crow.

Leo said...

Thanks Jamie. Interesting as always.