Q: What are you studying?
A: To help protect kestrels, we need to know where the birds spend their time. Currently, we have no idea where they prefer to hunt. Do they prefer hay fields or cattle pastures, for example?
There are nest boxes in places where people have established pollinator meadows. Do kestrels prefer those to farmed land? How far from their nest boxes do they go to hunt, and does that change when the hay fields are cut or as the meadows grow taller?
We want to help manage the land that’s available and make recommendations to landowners on how best to support kestrels. For now, we don’t know much about what kestrels need, other than just open space.
Q: How are you studying the birds?
A: Because kestrels are small, there really haven’t been tracking units scientists could put on the birds to collect this kind of data — until now.
We’re working with a company in Europe that makes tracking devices for animals. We have these tiny devices, loggers, that we fit on the kestrels like backpacks.
They’re miniscule. They weigh 3.5 grams (0.12 ounces, or between two and three paperclips). They have tiny little solar panels, so they can charge themselves, and tiny little antennas to record and transmit the location data.
We make sure that the trackers weigh less than 3% of the kestrel’s body weight and females are heavier than males. A female kestrel weighs about 140 grams (5 ounces, or a baseball), while a male weighs closer to 105 grams. (3.7 ounces, or a small onion). So right now, we can only put the loggers on the females. We’re interested in studying the males, too – they seem to move more widely than the females – but the units aren’t small enough yet.
This is a collaborative project between the Smithsonian Migratory Bird Center, the Smithsonian-Mason School of Conservation and the Clifton Institute.
Bert Harris, of the Clifton Institute, works closely with regional landowners on sustainable land management programs and is focused on applying our results to local recommendations. We also work with Alan Williams, a raptor capture and handling expert with a particular affinity for kestrels. He works for Shenandoah National Park as an ecologist, but he’s doing the project in his free time. We also have three interns doing data collection: downloading tracking data and sampling vegetation. We also have a great group of volunteers who help us monitor a large network of nest boxes.
Q: What makes studying kestrels challenging?
Kestrels are small and fast which means they aren’t very easy to watch. You’ll see them sitting on a power line or a fence post, but once they move, they’re hard to track.
Scientists have tried to study kestrels with banding. However, no one has been able to get detailed data to be able to identify the territories they’re using when raising their young. We know where they’re nesting, but we don’t know where they’re hunting or how they’re using the landscape.
Q: Are the birds OK wearing the tracker?
A: We are very conservative with the tracker design. This type of harness has been used on a bunch of species of birds for years. It’s the same kind of harness that the Smithsonian Migratory Bird Center uses to track birds flying to South America and back. There hasn’t been any evidence that the loggers are having any effect on the birds or their behavior. These particular units have been used on European and lesser kestrels in Europe.
Q: How do you get the trackers on the birds?
We put the loggers on the females when they’re sitting on the eggs in the nest boxes toward the end of the one-month incubation period. We collect just a few points per day until the eggs hatch and the female begins leaving the box more, allowing the unit to charge fully and collect more points per day. It takes about a month for the nestlings to fledge. At this point, all our nests have been completed, and nearly all our females successfully raised their young through the fledging period, which was encouraging to see.
We suspect some of the birds in this region actually migrate and some of them stay here all year long. The tracking information has already showed us that at least at this point, toward the end of August, the vast majority of the birds are still here, most of them still in their original breeding territory.