Some members of the Iowa City Bird Club want to create a team to install and monitor a small (pilot) set of about six American Kestrel nest boxes. During a discussion about this, some asked the following questions. I would be grateful for input regarding any of the questions.
- What approximate percentage of the American Kestrel population breeds and/or winters in the tallgrass prairie region?
- Is there evidence of pesticide harm to American Kestrels?
- What is the best time of year to hang an American Kestrel nestbox?
- Do kestrel boxes need to be far from bald eagle areas?
Hello! Welcome to the American Kestrel Partnership, and thank you for reaching out. We'll be happy to answer these and any other questions you have.
1) We don't know offhand the percentage of the population that uses the tallgrass prairie region at any given time, but we can definitely say that density of American Kestrels in this region—particularly in central Illinois, but also eastern Iowa and northern Missouri—tends to be higher than in much of the rest of the country. Additionally, the tallgrass prairie is one of the few strongholds in the US where the kestrel population is managing to hold steady. If this question was attempting to suss out how important your area is to American Kestrels, we can assure you that you're residing in very important kestrel country.
2) Certainly the banned pesticide DDT was a factor in the past, and there has been concern that newer pesticides such as neonicotinoids may be negatively affecting American Kestrels. However, kestrel declines first began in the 1960s while neonicotinoids weren't developed until the 1980s, indicating that they can't be the sole culprit. Additionally, the rate of kestrel decline has remained constant since the trend first emerged in the 1960s, which further sheds doubt on neonicotinoids as a potential cause of decline. If neonicotinoids were having a deleterious effect, the rate of American Kestrel population decline should have accelerated starting in the 1980s rather than remaining steady (unless another cause of decline abated at the exact same rate, a possible, though far from statistically likely scenario).
3) The best time to install nest boxes is during the non-breeding season, which is between October and January in most of North America. You can check out this link for more information about where, when, and how to install nest boxes.
4) We aren't aware of any studies that have specifically examined the relationship between Bald Eagles and American Kestrels on their nesting grounds. We can say that a kestrel would be fairly safe around a Bald Eagle, which typically prefer larger and more easily captured prey such as mammals, waterfowl, or fish, but all the same it's likely that a kestrel family wouldn't be too keen on having such as a large predator as a next-door neighbor. As a result we'd recommend keeping any new nest boxes at least a half-mile from the nearest eagle nest to make sure the two raptors' ranges don't overlap.
We hope that's helpful! There are currently just two boxes being monitored by AKP partners in the entire state of Iowa, so we'd love to have your team participate if you decide to go ahead with the project. If you have any other questions, please don't hestitate to reach out, either here or by emailing us directly at kestrelpartnership@peregrinefund.org, and we'll be happy to help.
Matthew, AKP Staff
Thanks very much, Matthew! I will relay the info you shared to interested parties.