Why does this red-tailed hawk throw up a long gray lump? Is he sick? Not at all. He’s casting a pellet.
Birds’ digestive systems are very different from ours, beginning with their beaks. Since birds don’t have teeth they swallow most of their food whole. The rest of their digestive system is geared to deal with this.
Birds have little saliva and few taste buds compared with mammals, which chew and physically process food as the first step and then subject it to chemical processing as the second step. Birds reverse this sequence. They start chemical digestion in the proventriculus [then the food] undergoes physical processing in the gizzard.Ornithology, 3rd Edition by Frank B. Gill, page 164
We chew with our teeth and spit out the bones. Birds chew with their gizzards which then collect the bones, fur, and other indigestible bits into a lump. The bird spits out the lump when it’s a convenient size.
Owls, eagles, hawks and falcons cast pellets but so do many other birds “including grebes, herons, cormorants, gulls, terns, kingfishers, crows, jays, dippers, shrikes, swallows, and most shorebirds.” (quote from Wikipedia)
Scientists examine pellets to find out what the bird ate. One of the long-eared owl pellets below was dissected to reveal the rodent bones inside.
For whatever reason, it’s rare to see a bird casting a pellet so consider yourself lucky if you witness it, as Chad+Chris Saladin did in the photos above.
A NOTE ABOUT HANDLING OWL PELLETS from Wikipedia: Some rodent viruses and bacteria can survive the owls’ digestive system so wear gloves and sterilize the pellets in a microwave oven before handling. A 2005 study found outbreaks of salmonellosis at elementary schools associated with dissection of owl pellets: Smith KE, Anderson F, Medus C, Leano F, Adams J, 2005. Vector-Borne and Zoonotic Diseases,5, 133–136.
(red-tailed hawk photos by Chad+Chris Saladin; pellet photo from Wikimedia Commons; click on the captions to see the originals)