20 Feb Why Weighing Birds Isn’t Just About the Number on the Scale
Weighing birds is one of those things we do every day, but it’s easy to fall into the trap of thinking the number on the scale is the ultimate measure of whether a bird is ready to work. In reality, weight is just data—it tells a story, but it doesn’t tell the whole story.
When we look at weights, we’re looking for trends, not absolutes. A bird trending up or down gives us information, but it doesn’t necessarily mean we need to react immediately. With Oakley, our Harris’s hawk, she can be successful at a variety of different weights given the season and what the job we are asking her to do. She is a very skilled, strong flyer, and we have a big range where we know she can still be successful.
How Do We Determine a Working Weight?
The short answer: it depends.
It depends on the bird’s species, age, the season, their fitness level, their role in the program, and how much skill they have under their belt. It depends on how they’re working—are they soaring? Are they building new behaviors? Are they in a holding pattern?
For birds of prey, ravens, and vultures, the goal is that they can work consistently while maintaining good body condition and even molting. Instead of a single number, we look for a range and work around that.
Looking Beyond the Scale: Keel Scores and Body Condition
Weight alone doesn’t tell us if a bird is in peak condition. A falcon and an owl might weigh the same, but their keel scores—the prominence of their breastbone and overall muscle tone—will be completely different.
I check keel scores all the time, probably more often than people realize. It’s second nature when I pick up a bird. I’ll check in on our hawks often —especially if something looks off. But because these birds have been working for years, I already have a solid baseline for what’s normal for them.
Weight Trends Matter More Than Daily Fluctuations
Weight is a tool, but it’s not the only one. A bird like Kipling, our Southern ground hornbill, has had a steady weight increase as he’s matured. If I only looked at his weight last year and tried to hold him to it, I’d be missing the bigger picture.
Rio, our king vulture, came in at 3,200 grams at 30 years old. We have increased her weight considerably over time and also noticed that as she has gained skills and consistency, the range in which is successful also grows. Birds with low training history and a high avoidance response usually need to be managed much more carefully compared to a bird like our eagle owl, who has a ton of flight experience and resilience in new situations.
The more skills a bird has, the wider the weight range we can work with because they have more ways to navigate challenges. Birds with fewer skills need a much tighter range to ensure success.
Weight Management Is a Conversation, Not a Directive
Adjusting a bird’s weight is never a one-person decision. It’s a discussion. It’s based on their workload, their conditioning, the season, and what’s coming up. If cold weather is on the way, we plan ahead to make sure birds don’t drop unexpectedly.
For birds in training, I always make sure their highest-value reinforcers are reserved for their most important work. When our yellow headed vulture is getting ready for an education program, he got the best food when he worked in that setting. If we ask for high-value performance, we need to match it with high-value reinforcement.
Seasonal Adjustments: Heat, Cold, and Training Changes
Winter and summer affect birds differently depending on where you are. In Alaska, birds might pack on weight in the winter to conserve energy. In Southern California, we see the opposite—birds often eat less in the heat.
That’s why we adapt. In the summer, some birds might shift to lower-energy education programs instead of high-output flight programs. Birds that handle heat well, like our saker falcon, keep flying, while others get a modified training schedule.
Why Avoiding Problem Rehearsal Is Critical
One of the biggest challenges in weight management isn’t just getting a bird to an ideal range—it’s preventing them from rehearsing behaviors we don’t want.
If Oakley goes into a hawk walk heavier than normal and starts ignoring cues or doing her own thing, she’s reinforcing avoidance. That means the next time, I’ll have to work harder to motivate her. Instead, I’d rather manage her weight proactively so I can reinforce the right behaviors and keep her in a positive training cycle.
Final Thoughts: Weight Is Just One Piece of the Puzzle
At the end of the day, weight is one factor to working with free flighted birds, but it’s not the whole story. We use it as a tool, but we don’t obsess over exact numbers. We focus on trends, body condition, motivation, body language, and the bird’s overall ability to do the work we’re asking of them.
Every bird is different. Every season is different. The key is flexibility, observation, and understanding that weight management is a dynamic process—not just a number on a scale. Our most important feature of the work we do is for our birds to have a healthy relationship with food and proper body condition. Signs of health don’t just include body score, but feather condition and care, molting, how often the bird bathes, and overall comfort.
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