Cherie Pittillo, “nature inspired”, zoologist, wildlife photographer, and author, explores nature everywhere she goes. She’s identified 56 bird species in her Merida, Yucatan backyard view. Her column, published on the 7th and 21st of each month features anecdotes about birding in Merida, Yucatan and beyond. Contact: email@example.com All rights reserved, ©Cherie Pittillo
“You’re a pigeon.”
“What? What do you mean, ‘I’m a pigeon.’?”
“I didn’t call you a ‘pigeon.’ I said,’uropygium’, (u-row-pidge-e-um). It’s the scientific name for the rump where the tail feathers grow. A preen or oil gland exists in most birds located just above their tails in the uropygium. It’s an uropygial gland. Ironically, many pigeons don’t have them.”
“What’s the big deal about a preen gland?”
“It’s a huge deal. If you depended upon feathers
or to attract a mate,
or to help protect against bacteria, fungi, lice and other feather parasites,
or to maintain the physical structure of feathers,
you would need a preen gland or another method to keep your skin and feathers in great condition.”
“Okay, thanks for the info. Goodbye.”
My conversation made me think about anhingas and cormorants. For decades I’ve read or heard that anhingas and cormorants lacked preen glands. I often saw these species with outstretched wings and believed what I had read.
I stood dumbfounded as I watched an anhinga at Merida’s Aqua Park use its bill to reach the preen gland and then rub the waxy substance over its body feathers. The substance contains waxes, fatty acids, fats, and water. It also seems that some secretions contain Vitamin D precursors. When the oil spreads over feathers, sunlight exposure activates the Vitamin D.
I also noticed how the anhinga used its neck and head in addition to the bill to rub across the preened chest and its back to distribute the supreme preen oil onto the head and neck. Look closely just above the anhinga tail to see the area for the uropygial gland.
As far as the cormorant, some scientists theorize their feathers are waterproof except the wing feathers which are wettable. With wettable wings the cormorant can dive deeper while the other feathers provide insulation thanks to its basic, but effective oil gland.
I’ve also seen ducks and other waterfowl smear the oil on their necks and heads, but didn’t realize what they accomplished until I slowed down to watch this time-consuming process. During preening, it’s also important to reach all the nooks and crannies, or with the flamingo, “necks” and crannies.
However, controversy exists whether waterproofing comes from the oil gland but rather that the bird straightens and fluffs dense feathers to form a water-tight surface.
And the controversy continues because the majority of birds have these grand glands, but some don’t; some have remnants, and some embryos show the glands but not after hatching. Glands are missing in emus, ostriches, cassowaries, kiwis, some woodpeckers, some doves, some pigeons, all Amazon parrots and other species. By the way, the two most common Amazon parrots in Merida, the White-fronted Parrot and the Red-lored Parrot, lack those rump bumps.
Even the gland structures vary as the waxy secretion empties onto the skin surface through one or more nipple-like projections. Some have small tufts of feathers associated with the pores and others don’t. The number of projections may vary up to 18. Check out the nub in the Squirrel Cuckoo as it squeezes it with its bill to get the secretion and then compare the different type of gland with that of the American Flamingo.
How do birds care for their feathers without oil glands or reduced oil glands? Some have downy feathers that break down into a feather dust. I wonder if Amazon parrots were the original feather dusters. Anyway, the dust contains a fine, white waxy powder containing the protein, keratin. Other oil glandless birds may use dust baths.
But wait, there’s more! Scientists in Spain studied the Greater Flamingo to theorize secretions from the preen glands enhance the plumage color during mate selection and suggest it’s the equivalent to the use of make-up in humans. Plus the courting male may twist his neck backwards to use the bill to preen feathers quickly in front of the female in a twist preen to attract her.
I think it’s safe to say that the functions of the uropygial gland differ among species and within some species. What scientists do agree is that birds spend a lot of time in maintaining their feathers whether with the preen gland secretion, powder dust or dust baths.
GO OUTDOORS TO PREEN YOUR SOUL>>>
DISCLAIMER: References do not agree on details about this species. Here are my resources:
Juan A. Amat, Miguel A. Rendón, Juan Garrido-Fernández, Araceli Garrido, Manuel Rendón-Martos, Antonio Pérez-Gálvez. Greater flamingos Phoenicopterus roseus use uropygial secretions as make-up. Behavioral Ecology and Sociobiology, 2010
Revista Brasileira de Ornitologia, 21(3), 162-167
Elder, William H. Oil Gland of Birds. The Wilson Bulletin, 66, (1), 6-31, March, 1954
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