If you’ve ever had the opportunity to see a bird of prey up close, you’ve probably noticed one of the key attributes that makes a raptor a raptor… those feet! Handling birds equipped with sharp talons comes with some inherent risk. So, why do we do it?
Having a raptor in-hand gives you an opportunity to appreciate all the features that make them such well-adapted predators. Their impressive feet, sharp beak, incredible eyes, and all the unique variations in plumage can really be admired when you get up close and personal. However, as wild birds, the admiration is not mutual, they would rather not see us that close at all. When we catch a raptor and handle it, we are disrupting its normal behavior and, admittedly, causing it some stress in the process. As researchers, we have to weigh the benefit of capturing and handling a wild raptor against the risk for both the researcher and the study species. When we decide to capture raptors, it is because it is the only way to gather the essential data we need.
Banding
One of the most common reasons we handle raptors is to band them. Banding raptors involves securing a metal band with a unique identification number to one of the legs of the raptor. In North America, these bands are issued by the USGS Bird Banding Laboratory and the Canadian Bird Banding Office. These bands can typically only be read if the bird is recaptured later in its life or found dead. The limitation of only being able to read that number while a bird is in-hand is that catching a raptor once is hard enough, but capturing them multiple times is even more challenging! Recaptures are relatively uncommon, but do happen, and once a band number is submitted, you are able to find out where that bird was initially banded and when. If you see a banded raptor you can report it to us here. Resighting banded individuals provides some information on how old the bird is and where it has been. To make resighting individuals more accessible, researchers will often use color bands. These bands are secured to whichever leg doesn’t have the federal band and typically consist of a solid colored band with a combination of numbers and/or letters. These can be read through binoculars, scopes, or a telephoto lens and can also be seen on trail camera photos. For more information on banding and auxiliary markers, check out this blog by HawkWatch International (HWI) Field Biologist Kate Sweet.
Transmitters
In addition to bands, we can use transmitters to give us even more detailed information on movement by providing exact GPS locations of where an individual raptor is. By tracking locations and movement, we can identify important areas for species throughout the year (migration routes, wintering areas, nesting areas, etc), understand home ranges of various species and individuals, and even help identify risks to raptors (see HWI’s Eagle Vehicle Strike project). Transmitters provide fascinating and vast amounts of data, but require experience and training to safely attach to the raptor. Most transmitters are worn by the bird on a harness similar to a little backpack. Some are only worn for a short time, but others are intended to stay on the bird for their entire lifetime. Either way, having expert raptor handling skills is a must for safe transmitter deployment.
Measurements and Health Assessment
Once we have caught a raptor, we will take a variety of measurements, including weight, wing chord, tail length, hallux (“killing” talon) length, and culmen (beak) length. This can help us determine the sex of the birds, as female raptors are typically larger than males, and gather general information on variations between species or populations. The bird is also given a quick health assessment. The most common health factors checked are the bird’s keel (breastbone), wing-pit fat (area under the wing where you can see a bird’s fat storage), and crop (where raptors and some other birds initially store food and begin digestion). This will give us an idea of the bird’s overall health and condition. Having a bird in hand also provides the opportunity to take feather samples, blood samples, mouth swabs, etc. These samples can be used to answer any number of questions, such as what a bird is eating or whether they have been exposed to toxins such as lead or rodenticides. This information can answer questions about various species’ biology or identify potential threats to raptors.
Bird Safety
At HWI, we always prioritize safety for both the researchers and the raptors. When we do handle wild raptors, we work efficiently and gather as much information as possible while keeping the bird calm and relatively comfortable through what is no doubt a very strange experience for the bird. We can utilize tools like falconry hoods to cover their eyes and ears, which immediately calms these highly visual birds. Cans function similarly, keeping the bird calm in a dark, ventilated, appropriately sized can that can make the banding and processing more efficient for the bander. We are also very conscious of the time. Typically, a bird can be measured, banded, and released in as few as five to ten minutes, but when taking other samples like blood, or deploying a transmitter, handling time increases. Paying close attention to the bird’s attitude to note any signs of stress is extremely important, especially during longer handling times. If a bird is becoming overly stressed, we may suspend the extra measurements or decide not to take blood or attach a transmitter to minimize handling time and release the bird as quickly as possible. As important as the data we want to gather is, we would much rather release a bird before stress begins to risk its health and safety.
Seeing a raptor in-hand is an unforgettable experience and can be inspirational for those interested in raptor research and conservation. There is valuable information gained and research questions that can really only be answered by having a bird in hand. Personally, one of the most rewarding parts of having a bird in hand, is when it comes time to release it. I love seeing them spread their wings, rouse their feathers as if to shake off the experience, and return to soaring through the skies.
This blog was written by Frankie Vierela, one of HWI’s Field Biologists. You can learn more about Frankie here.
