Blog #441 Preen to Clean

June 05, 2023

She begs, and he obeys. No longer acting like a bachelor, Orpheus dutifully brings home fresh fish to Ursula, maintaining family harmony. The happy homemakers continue caring for their nestlings, tending their nest, and repealing would-be nest usurpers. There’s a lot of down time and only one thing to do—preen.

Orpheus preening his primary feathers, courtesy of Steve Gee.

All birds preen, and it’s not just to look good: their survival depends on it. Ospreys can’t fly if their feathers are wet from rain or diving for fish. To keep their feathers in top shape and waterproof, ospreys have to spend hours spreading waterproofing preen oil (uropygial oil) on their feathers and grooming them.

Preening osprey, courtesy of Loree Johnson.

Preen oil is a thick, transparent, complex oil consisting primarily of diester waxes (uropygiols), fats, and fatty acids. The gland is located at the base of the tail, on the lower back, just in front of the tail feathers. This area is generally featherless except

Nipple-shaped uropygial or preen gland of an Osprey (left)

and a chicken (right), courtesy of Osprey Tales.

Anatomy of a feather, courtesy of Wide Open Pets.

for a tuft of down at the tip called the uropygial wick. This two-lobed gland secretes oil through small papilla or nipple-like projections.

When preening, the osprey gently smooths each feather into its place, adjusting and waterproofing them for flight and insulation. Whenever the barbs are disturbed, the osprey uses its beak to carefully guide or zip them back into place one by one, much like Velcro strips coming together. The bird rubs its bill and head over its oil-secreting uropygial gland and then spreads this oil over its feathered body, wings, legs, and feet to keep the skin and feathers conditioned. While preening, ospreys contort to access hard-to-reach spots, twisting their heads 180°, often appearing headless.

Scratching with their long, curved talons looks dangerous, but it removes ectoparasites, dead skin, caked on feces, and debris when bathing is not an option. Scratching also

Orpheus preening with eyes closed, courtesy of Cindy Sedlacek.

relieves itchy insect bites, especially from the mosquitos, which plague ospreys at night. Ospreys close their white feathered eyelids while scratching and preening to protect their delicate, yet powerful, eyes.

To prevent their feathers from becoming water-logged after diving, Ospreys give a rapid doggie-shake, shedding most of the water. Why is shaking so effective? Osprey feathers’ lack aftershafts (see anatomy of a feather above), the small extra feathers at the base of larger feathers on most birds. Without them, water sloughs off ospreys easily.

Researchers studying this phenomena have likened the surface of feathers to the perfect water repellant raincoat. Feather surfaces are covered with miniscule nano-sized grooves, which trap air around the feather, preventing liquids from attaching to the wing surface.

Scratching with eyes closed by CE Cornell.

Water droplet beading on top of the nano-sized grooves in a feather, courtesy Jenssen Lab.

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Preen or uropygial oil waterproofs by further repelling the water droplets from the feathers. When an osprey forcibly shakes, their moving skin and feathers produce energy that physically breaks the weak attractive forces holding the water molecules.

This act of physically cleaving these weak hydrogen bonds, called “mechanochemistry”, propels the water off the feather surface. The doggie-shake whips clinging water droplets off the osprey’s body.

Osprey bathing, courtesy of Stephen & Judy Shelasky.

Orpheus giving a quick doggie-shake after his bath to dry off.

Eyes to the sky!

Candace

Candace E. Cornell

Friends of Salt Point, Lansing, NY

Cayuga Lake Osprey Network

cec222@gmail.com

Guest Photographer:

Cynthia Sedlacek, musician and Director of Data Administration and Reporting at Cornell University, is a surprising artistic talent. Cynthia’s affection and admiration for raptors are evident in her exciting photographs primarily of Ospreys nesting around Cayuga Lake and the red-tailed hawks of the Cornell Campus. Her photographs of local Ospreys are incomparable as she captures their essence, their jizz, and their inner bird. From the hard-to-see nestlings to the fast-flying adults, Cindy goes beyond the pale to catch all aspects of Osprey life in the Cayuga Basin. “My camera allows me to capture their beauty in many ways that the human eye can’t see,” she says, “like their spectacular wing positions and detailed feather patterns.” Cindy and her husband Karel are also avid nest monitors for the Cayuga Lake Osprey Network and video stream footage of the campus hawks.