Molt

IMG_7104.JPGTwo large feathers fell to the ground in Carson’s mew this week, marking the beginning of her annual molt. Over the next few weeks she will drop all of her feathers to grow a new set. This most recent molted pair of feathers mirrored each other: one curved to the right, one curved to the left. The shape tells me the feathers came from her wings: one from the right wing, one from the left wing.

The asymmetrical shape is most pronounced in the primary flight feathers, those farthest out on the wing where her fingers would be. If we take a look at “P10,” the outermost primary feather, we can clearly see the center shaft running closer to one edge of the feather vane:IMG_7111.JPG

As the bird flies, this is the first feather to cut through the air and the narrower vane (the top side in this photo) will be the leading edge. (So we know this feather came from the right wing.) The asymmetrical shaft assists with aerodynamics and feather stability in flight. One of the next primaries has a slightly different shape:IMG_7110.JPG

The shaft is still asymmetrically placed, but both leading and trailing edges have notches that make the tip of the feather more narrow. When the wing is spread, these outer feather tips separate like individual fingers to reduce drag. It seems amazing that these feathers are so well designed to optimize efficiency in flight.

Find out more about identifying feathers at The Feather Atlas website.

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Feaking

After eating a meal in the sun, Carson the Red-tailed Hawk demonstrated “feaking.” A strange but traditional falconry word, feaking simply describes a hawk rubbing her beak on a perch to clean it.  This behavior is most often seen after eating to scrape off any bits of food stuck to the beak, and is also a sign of comfort.

April Blizzard

A blanket of snow covered the mews after last weekend’s hefty snowstorm. Even Aldo’s mew, where the skylight is covered for the winter, had a dusting thanks to the strong winds carrying a taste of the blizzard inside. Carson and Theo got the full force of the storm through their open skylights. I saw footprints on the ground and ramp in Theo’s mew; in typical owl fashion, he didn’t seem to mind. Carson the Red-tailed Hawk chose to stay elevated on perches. Her snow piles remained untouched until I swept the ramp clear with my mitten. I wondered what she was thinking as I took this photo.

She might share the same attitude as most people that spent the April weekend shoveling. “Are you kidding me?”

Or does she appreciate the snowfall as a magnificent form of enrichment? “Isn’t this interesting!”

Or, perhaps more likely, she thought of more pressing matters. “So, when will my food be delivered?”

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Foot Tuck

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I am always looking for signs that the birds are relaxed. Any time their head is down (while eating) or covered (while preening their wings or sleeping), they are more vulnerable to a threat. A predator might take that opportunity to launch a surprise attack, so they only risk covering their eyes when they feel safe. Other comfort behaviors, like Carson’s foot tucked in the photo, indicate that they are comfortable and and not worried about their surroundings.

Sleeping

I went outside to check on the birds one last time before I went home for the day. I peered into Carson’s mew and saw her staring back at me as usual. But this time, she quickly looked away to snuggle her beak back behind her wing to fall asleep. I don’t often see the birds so sleepy, so I was excited to get her “bedtime” on video!

 

Pellet Schedules

Ready for a rousing game of “Who Cast that Pellet?”  Take a guess with this first pellet:

Pellet #1:

Theo pelletSee the bone fragments poking through this pellet? Theo the Great Horned Owl left this after eating a furry white rat. His stomach muscles and juices broke down the meat, allowing the meal to continue into the intestines. But indigestible fur and bones remained in the stomach where they were pressed together and, eventually, coughed back up. The time required for this process depends on the size of the meal: larger meals take a longer time to process.

Pellet #2:

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This pellet has smoother edges and no visible bones. If I split this pellet open, we would only find fur. Carson the Red-tailed Hawk ate the same meal as Theo, but hawk stomach acid is much more acidic and can disintegrate bone. The bones of her rat passed through, but the tough fur was still cast back up as a pellet.

While owl pellet schedules depend on when and how much they eat, hawks adhere to a circadian rhythm. In one study, Red-tailed Hawks cast a pellet at the first light of the day regardless of when they were fed the day before. They are even known to cast a pellet after a fast day with no food in their system. Their routine pellet casting at dawn may reflect their hunting strategy. Hawks require daylight to hunt, so emptying their stomach in the morning will prepare them for a fresh meal. Owls, on the other hand, can hunt during day or night, so their system simply empties after the food has been digested.

Learn more about raptor pellets in this Raptor Physiology chapter.

Changing eyes

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Carson’s eyes were the subject of my very first “News from the Mews” article in 2016. I had never met a young hawk before, and her light-gray eyes were strikingly different than what I was used to. Red-tailed hawk eyes darken as they age, and the older hawks I knew had nearly black eyes. We’re starting to see this effect with Carson. Now nearly 5 years old, her eyes are becoming a deeper shade of brown. The lighter shades are still speckled around the iris, and I expect they will continue to darken as she ages.