The American Kestrel Partnership was created by The Peregrine Fund to gather data about the very alarming decline of American Kestrels in North America. Long term data from breeding bird survey routes indicate as high as 64% population decline in American Kestrel populations since the 1960’s. As with most declining species, it is likely a combination of factors that is causing the downward trend (competition for cavities, landscape changes, etc.) so it is hard to pinpoint any one real cause, especially without detailed long-term data regarding nest success/failure and more specific information about adult life histories (Problems during breeding, migration, wintering habitats, or all three?). The partnership focuses mainly on collaboration and research through American Kestrel nest box monitoring with a goal of collecting the long-term data needed to begin to answer these questions. For much more information regarding American Kestrel Research and population trends, please visit the American Kestrel Partnership main page, which you can now find a permanent link to on our side bar.
American Kestrels are by far my favorite species of raptor, so I am particularly interested in nest box studies and long term monitoring efforts in regards to their decline. I may be quite partial, because this is my second year of monitoring Southeastern American Kestrel nest boxes in north central Florida. It is truly a privilege to be able to peek into the breeding life of a cavity nesting species. I’ve spent a lot of time with young kestrel chicks, taking photos of young chicks for aging purposes which helps to answer questions regarding nest success. From the outside, a cavity or a nest box seems like a very safe place to raise a clutch of chicks, but American Kestrels face many obstacles, even before they hatch. A myriad of predators are smart and lucky enough to get into nest boxes and cavities, and if eggs can make it to hatching, chicks still have to deal with predators, and even each other. Competition within a nest box among siblings is very intense, and it is truly survival of the fittest even within the relatively small confines of the nest box.
Atop the Research Library at the Peregrine Fund’s World Center for Bird’s of Prey near Boise, Idaho (a must-visit if you are ever in Boise), this has all played out for people any where in the world to watch over the past two months on The American Kestrel Partnership Kestrel Web Cam. A pair of American Kestrels moved in early in the season, and by April 1st the female was already defending the box from a European Starling (watch the epic battle here). By April 23rd, the first of five eggs was laid by the female, and by May 25th, two of the five kestrel eggs in the nest box began hatching.
One day after checking some kestrel boxes down here in Florida, I got home and checked the web cam to see the progress of the chicks (perhaps I have a problem….). They were about ten days old at the time, and they were already battling over a small rodent. One chick had spent nearly ten minutes trying to get it down, when another chick nonchalantly grabbed it from its mouth and downed it within a minute or two (while the other one still tried to pull it out). This is the behavior my quick nest box checks miss; the intense competition among chicks as they grow. By watching the nest cam, it is easy to see the struggle for survival intensify over time. It is amazing to be able to look into this box at any time thanks to the web cam, but I thought it would also be great to see this progress in a handful of short video clips. Chris McClure of the Peregrine Fund and Delora Hilleary of the American Kestrel Partnership were more than willing to help out with this as a post for Nemesis Bird, so I thank both of them and The Peregrine Fund for taking the time to coordinate and put these amazing clips together to share with us!
Early on in week one, the nest box was a relatively calm and subdued environment, and the kestrel parents took time to feed the chicks by very meticulously ripping off small bits for them. The chicks didn’t move all that much, and this is apparently when the latest hatched chick can start to be at a disadvantage if it can’t poke it’s head up between the others for a bite.
American Kestrel chicks feeding: Day 1
This is down right adorable. It is amazing to see the “softer side” of an adult kestrel, which is otherwise a small killing machine. The chicks really just waited for food to be placed directly into their mouths.
American Kestrel chicks feeding: Day 5/6
These chicks are still basically in the exact spot that they hatched, but you can see the struggle starting. Larger chicks were able to stretch their necks out just a little farther for that extra bite, but it really still depended on where the adult stands while feeding, who gets the bulk of the meal.
Throughout week two, kestrel chicks became very mobile and it was very comical to watch them “wobble” around the nest box. As much as they are in competition with each other, they always end up back together in a little bunch to take naps. With age they start to become much more aware of their surroundings, and you can see them start to key in on the movement of their parents as soon as they hit the cavity entrance. The adults still tried their best to distribute food among as many chicks as possible, but this didn’t always happen if the prey item was smaller.
American Kestrel chicks feeding: Day 11
The first clip shows a large chick nabbing an insect from the adult females mouth, only to have the adult take a few bites out of the chicks mouth to give to other siblings. In the second clip, a rodent is dropped off, likely for chicks to start trying to eat themselves (believe it or not they can down a rodent WHOLE at a very young age). In the third clip, the female takes time to feed the chicks. In all of this, note that the youngest/smallest chick is less alert than the others, and tends to end up at the back of the bunch, missing vital parts of the meal.
Here is a photo of a 12 day old chick that completely downed an entire mouse in Florida in 2012. Keep in mind this chick is only about a day older than the larger chicks in this video clip. He looked like he needed a TUMs after he ate it.
After day 11 and 12, chicks really turn into little monsters. But remember, they have a reason for acting this way; they don’t want to starve. Chicks become alert when they hear the adult coming, and prey deliveries are quick and happen mostly at the cavity entrance. It can take a lot for the parents to keep five growing chicks continually supplied with prey items. When larger chicks dominate prey deliveries, smaller chicks can end up missing many meals. Unfortunately, this may be what happened to the youngest chick in this box on June 18 when the chicks were about 22-23 days old; the chick died, and was then eaten by its siblings (This is very common in the raptor world; read more about it here). While the previous videos could be viewed as fairly cute and comical, the struggle to survive is no joke, and the final video clip captures the very somber reality that faces many kestrel chicks all over North America. In different habitats across North American, prey availability is likely a very real concern for American Kestrels and their ability to successfully fledge chicks, and while it is fairly common for at least one chick to die of starvation, it can easily happen to more of them within a box.
American Kestrel chicks feeding Day 18
This clip was taken about five days before the youngest chick died. The youngest chick is now very obvious; note that its feathers are less developed and it has the most downy white feathers still left on its head and body. It is hard to say if this is the chick that hatched last, but somewhere along the line, likely from very early on, it missed more meals than anyone else. If it was the last chick to hatch, it was already at a real disadvantage. In the first clip, we see an insect delivered to the entrance, and a larger chick jump up to grab it. In the second clip, the chicks are very violently fighting over a small rodent. You can tell that the youngest chick will do anything to get even a small bite of these prey items. It even throws itself in the middle of the battle with its bigger siblings; at this point it is very clearly worth getting stepped on to get the food it needs. In the last clip, the youngest chick isn’t as bold, and only takes a stab at the prey item a few times. From this clip you can really start to understand one of the potential reasons that this chick died; it likely got to the point that it missed too many meals and no longer had the energy to keep up with its larger siblings during feeding time. However, the death of the chick means that its siblings now have a much higher chance of surviving to fledging due to the lack of an additional mouth consuming the food they need to survive.
Right now, the kestrel chicks are about 25-26 days old, and they are literally about to “fly the coop.” Kestrels fledge around day 27, but it can often take a few days extra for younger chicks to get the nerve up to take the leap. All raptors have a notoriously high mortality rate in their first year, so their struggles are nowhere close to being over, as they learn how to hunt on their own. I look forward to hearing more about these chicks as they fledge and seeing the kestrel family again next season!
Please consider donating to the American Kestrel Partnership through the Peregrine Fund. It takes much time, effort, and resources to continually have the ability to monitor American Kestrels over time, and your donations will go a long way through the Peregrine Fund to help in their research efforts to better understand the decline of Ameican Kestrels.
Thanks again to The Peregrine Fund for these amazing clips and for providing this kestrel web cam for all to view. Be sure to watch the kestrel web cam VERY CLOSELY over the next few days as the remaining four kestrel chicks take the leap of faith into adulthood!