I couldn’t resist taking this picture of Carson yesterday, even though it creates a rather backwards story. Last week’s article described pellet formation in raptors; now I’d like to hit the “rewind” button to see what happens to the food right after it is swallowed.
After swallowing a rat, Carson’s meal slides down to rest in her crop, a very elastic portion of the esophagus that is used as temporary storage. The crop becomes apparent after a large meal as it fills and forms a bulge under her throat (see the arrow in the photo).
The food will slowly make it’s way into the bird’s two-part stomach. First is the proventriculus, where digestive juices start breaking down meat and bones. It will next pass into the ventriculus (also known as the gizzard). This section is known to be the grinding stomach for many birds, where powerful muscles crush food to aid in digestion. The meat in a raptor’s diet is relatively soft compared to tough seed diets of some birds, so the raptor’s ventriculus is less developed. They rely more heavily on chemically breaking down their food than mechanically crushing it.
The disintegrated meal will continue into the intestines where nutrients will be absorbed. The undigested fur stays in the ventriculus where muscles wring out extra liquid, then compact the fur into a pellet to be cast later.
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