Spring Cleaning

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In spring, I love to find wildflowers blooming, to wait for migrating birds to return, and (perhaps most of all) to connect the outdoor hose. Winter makes a frozen mess in the raptor mews that we try to clean with buckets of hot water, but we can’t get everything. The birds don’t seem to mind since they spend their time on perches, elevated above the muck. But it was clear to us they required a heavy spring cleaning. We spent a full morning this week rinsing, washing, scrubbing, raking, and disinfecting every surface of the mews. With the help of above-freezing temperatures and a little elbow grease, the mews are practically sparkling!

Weights

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Animals are amazing actors with the ability to mask injuries and illness. They want to hide any weakness from potential predators or competitors, while still finding their basic needs to survive. Raptors will keep hunting for food even with extreme injuries. When our Great Horned Owl, Theo, was rescued, he appeared to be well fed. The rehabilitators believed he was actually running down mice despite having a broken wing. Since their behaviors rarely show signs of illness, their weight is often the first sign of a problem. We take daily or weekly weights to track our birds’ health. The key is knowing what is normal for each bird.

I chart each bird’s weight to keep an eye on patterns. Aldo’s chart, for example, shows daily fluctuations and seasonal changes. His weight last summer hovered around 108 grams (3.8 oz) and increased in November. The higher weight gives him a little extra buffer against cold temperatures through the winter. As spring approaches, he has begun shedding weight in preparation for breeding season and warmer weather. With a baseline of these normal weight patterns, I can identify abnormalities and keep him at healthy weight.

Who’s awake?

Deep in the middle of winter, Great Horned Owls are already planning for chicks. Pairs begin singing duets in November to strengthen their bond before the first eggs are laid in late January or February. It is difficult to distinguish males and females in daylight since they have the same plumage (and females are slightly larger), but their calls provide hints once the sun goes down. The owls take turns calling into the night, repeating a phrase that sounds like “Who’s awake? Me too.” These calls are usually very distinct; males have a low-pitched voice compared to the female.

We are fairly sure that our Great Horned Owl, Theo, is a male based on his body weight, but the true test will be comparing his voice to another owl. Jayme, Living Collections Assistant, heard two Great Horned Owls, probably Theo and a wild bird, conversing in Cable earlier this week. We’ll have to listen again to find out if he is courting a high-pitched female or defending his territory against another deep-voiced male.

 

Cold Snap

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We eased into December with some mild winter weather, but this week gave us a good reminder of our northern latitude. Red-tailed hawks and great horned owls are common winter residents in Wisconsin. Owls are perhaps the best suited for winter with masses of fluffy down and extra feathers covering their toes. The wild barred owls that I hear calling in my backyard can cope with these temperatures, but our birds’ ability to stay warm is compromised by their permanent injuries.

Both Carson (red-tailed hawk) and Theo (great horned owl) had broken wings that never healed properly. It not only affects their ability to spread the wing for flight, it also means they cannot fold the wing completely. When standing on a perch, they can’t fold the wing against their body as usual, leaving an open door for the cold air. It might be the equivalent of you putting only one arm through your winter jacket and stepping outside. Since they can’t keep one side as warm, we give our birds the luxury of indoor heating when the outdoor temperatures dip below -10oF.

Inside a Training Session: Not Interested

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Sometimes training sessions go really well with big breakthroughs like the session I described with Theo last week. But sometimes we just don’t get anywhere. Here is an example of another session with Theo that was not as productive:

I stood outside and peered into the mew. His yellow eyes almost seemed to glow as he stared back at me cautiously. After making sure I was staying put, he turned away to watch the backyard. I silently willed him to turn his attention to the chunk of mouse sitting next to him on the perch. My mind controls proved ineffective, however, as something else caught his eye. He bobbed his head down, then stretched every one of his fourteen neck vertebrae to capacity as he reached his head to the left. Eyes wide, unblinking. I also swiveled my head around, searching for what would be so interesting to an owl. Did he just now notice the two men sitting quietly by the library? Otherwise the backyard was quite peaceful. Perhaps it was something inside the mew. Would a rogue fly warrant such focused attention? Finding nothing alarming myself, and Theo’s neck still stretched out as far as it would go, I tried to gently refocus his attention with more than mental vibes. I shuffled my feet, quietly crunching the gravel to remind him that I was still there and this was a training session. No luck. His eyes were still round globes locked on something more interesting than me.

Inside a training session: Theo learns the rules of the game

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Theo’s training log helps me keep track of his progress.

I wait patiently just outside Theo’s open door. To avoid a direct gaze that could be intimidating, I stare at the ground and count in my head: 34…35…36. In my peripheral vision I can see Theo completely ignoring the two pieces of quail meat sitting on the perch two feet away. He simply rests with one foot tucked deep into the fluffy feathers on his belly. 86…87…88. I am starting to get worried. All he has to do is walk over and eat the tidbits, but his window of opportunity, 1 minute and 45 seconds, is closing in fast. Unfortunately he seems quite content to keep watch over the quiet backyard. As my internal count reaches 105 seconds, I sigh and take a step forward. Theo instantly turns to me. I reach out with the forceps to take one tidbit from the perch. Theo’s eyes lock on the retreating meat and follow it all the way back to the pouch hanging from my belt. Before I can move again Theo places both feet firmly on the perch and his head begins to swivel quickly back and forth between me and the single tidbit left on the perch. He knows I am about to take it away. I pause. Finally he makes his move and walks down the perch to grab his food. I smile at this bold move and give him more quail as a reward. I marvel at how much this owl has learned in the past few weeks. He has learned enough about me to actually predict my behaviors and act to change them. Owls may not be known for their intelligence, but they certainly are not “bird brains!”

The Mouse Went Down the Hole

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Imagine a hawk sitting on a fence post along the edge of a cornfield. Scanning the ground beneath her, she suddenly spots a mouse and must decide whether she will chase it or not. There are several factors that influence her decision. First, is she even hungry? If she just finished eating a rabbit, she probably won’t feel the need to work for an extra snack. She also considers if it is a desirable piece of food, whether the tiny mouse is worth her effort, and if she can obtain it without injury to herself. Now if she takes too long to consider all of this, she runs the risk of the opportunity disappearing completely: the mouse could scurry down a hole, out of reach. She will learn to think faster next time!

This “mouse went down the hole” theory is a useful tool in training our raptors. Knowing that their food may disappear, they are more motivated to act quickly. While station training Theo, I placed a piece of meat on a particular perch and gave him 5 minutes (his “window of opportunity”) to come eat it. If he didn’t move by the end of the 5 minutes, I took the food away, just like the mouse escaping down the hole. He learns that he must move before the 5 minutes are up if he wants the tidbit. I gradually shorten his window, working it down from 5 minutes, to 4 minutes, and eventually to a few seconds. I am happy to report that he is currently coming to his station as soon as I set the food down. In just a few weeks, he decided that he is not going to let those mice slip away!

Photo by Vera Domingues/Hopi Hoekstra