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!

 

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Perch Variety

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Aldo tried out two new perches this week to spice up his time indoors. First he sampled a flat block perch for an afternoon, then he tried out a small hemlock branch that I bent over his normal perch. New substrates keep him engaged, test his balance, and promote foot health. Wild raptors perch on a variety of branches, wires, fence posts, and ledges, constantly changing how weight is distributed on their feet. Captive birds also need options; otherwise they risk developing pressure sores that can develop into swelling called bumblefoot. Aldo has one favorite perch, but it is beneficial to switch things up every once in a while.

Falcon pellets

Learning about digestive systems and pellet schedules is interesting (at least for me!) and it is also useful to know when caring for the birds. This week Aldo the American Kestrel wasn’t interested in training and wouldn’t take any food from me. This odd behavior could have multiple explanations. Did he suddenly decide to boycott quail? Was he overweight or sick? Or did he just need to eject a pellet? Soon enough, he opened his beak. With a little cough, he shook his head and flung this tiny pellet at my arm. He simply had to empty out his digestive system to make room for more food.

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Occasionally Aldo’s pellet isn’t a pellet at all. Sometimes he coughs up a few pieces of gravel. Oddly enough, this is a normal behavior, especially for falcons that often pick around feathers, fur, and bones on their prey. Without these materials to form a pellet, falcons replace them by ingesting small stones to clean out their crop. Knowing this tidbit of their natural history keeps me from being alarmed whenever it happens with Aldo. Instead I marvel at a bird’s ability to take care of itself, even if it means eating gravel from the floor of the mew.

 

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.

Nighttime Displays

generic GHOW.jpgDuring daylight, a Great Horned Owl’s most prominent colors are its mottled brown and black hues. This camouflaging pattern keeps the owl hidden so it can get a good day’s rest. Without it, the owl might be spotted by angry crows or blue jays and get chased away from its roost.

As the sun goes down and the owl wakes up, the forest – and the owl itself – is draped in a new light. The owl’s dark colors and fine patterning nearly disappear in low light conditions. Instead, it is the white throat patch that stands out. For nocturnal animals, contrasting blacks and whites are the most visible and can serve as a warning coloration, just like poisonous monarch butterflies are brightly colored in daytime. Picture a skunk’s bold black and white stripes that act like a spotlight in darkness, highlighting an animal that you would do well to stay away from.

I have yet to find an official explanation for the Great Horned Owl’s relatively bright throat patch, but I have my own theory. When resting, the patch appears as a thin line, perhaps minimizing the bright color to help camouflage while hunting. But when the owl needs to defend its territory, the throat inflates as he calls out a low “whoo-whoo whooo whoo whoo,” and the white patch expands to make a visible display in addition to the audible proclamation.

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Theo rested in the classroom overnight this week to escape the cold temperatures. You can most clearly see his white throat patch in the photo (and the white rope covering his perch).

2017 in Review

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Looking back at all of my “News from the Mews” articles from 2017 is a testament to what we can accomplish in 365 days. Carson gained confidence on glove and the snakes got help shedding their skin with added humidity. We saw changes in the seasons and wildlife, from a robin boldly defending its nest in spring to tracking nighttime visitors in the snow. The birds traveled to Minnesota and visited Cable’s Fall Festival, played with new enrichment items, and received windows and skylights in their mews.

In addition to the happenings of their daily lives, our living collections taught 85 programs this year and reached a total of 2,206 visitors. With all of their hard work, I think they’ve earned a relaxing winter!