What are birds doing when they turn around to nibble or rub their heads on their lower backs? Checking for “unsightly” smells? Inspecting their new tribal pattern lower back tattoo? Jokes aside, there’s an oil gland there. Birds, cursed by a lack of dexterous forelimbs, must use their heads and beaks to anoint their feathers with a clear, oily exudate produced by this small gland. Ok, so not all birds—pigeons, cockatoos, African grey parrots, and a few others—lack a uropygial gland and use a substance known as “powder down” to help them keep their feathers clean.
This structure, known scientifically as the uropygial gland (or in lay terms, preen gland), is critical for waterproofing feathers (allowing waterbirds to float), and facilitates the removal of dust and grime from plumage while preening. Clinically, this organ rarely presents with pathology (though some veterinarians have unfortunately removed healthy uropygial glands thinking they were tumors!) but can be susceptible to infection, cancer, or impaction, as we saw on day one of a visit to Wildlife Prairie Park (WPP) during a college professional development program.
Our very first patient on Monday morning of the WPP rotation was a Barn owl (Tyto alba) that served as an education animal for the park. Outwardly this owl looked completely normal, though a wave of surprise swept through our group as a tuft of feathers was lifted over the bird’s lower back and a marble-sized, fleshy pink mass sat glaring back at us like a creepy pearl in a weird feathery oyster. The gland itself, though enlarged, did not appear inflamed or lumpy, there was (thankfully) no odor, and overall the bird’s feathers appeared very well kempt. You must understand, however, that a veterinarian’s curiosity rarely allows them to say “hmm, that’s strange, let’s move on.” Combine that with a fiery passion we all seem to share for expressing viscous substances out of abnormal tissue. (Ask the next veterinary professional you see to describe the first time they lanced a big abscess and watch their face light up as they gleefully recount how satisfying it was.)
While interesting findings that turn into mundane diagnostic results can be frustrating for the clinician’s insatiable appetite for information, they often imply a better prognostic outlook for the patient, so I was able to live with the case of the “boring” enlarged uropygial gland (soon to be adapted into a new Hardy Boys novel). With the help of some anti-inflammatories (expressing any impacted structure tends to make the surrounding skin a little angry), the owl should be able to live with that too!
—Zach Kline, fourth-year DVM student