Merlin. Photo © John Picken / www.picken.com
Last week, the Field Museum Bird Collection received a batch of specimens from Willowbrook Wildlife Center, a wildlife rehabilitation facility in the Chicago suburbs that has been a long-time partner of ours. Not every animal that enters the rehab facility survives, and when they don't, they end up as research specimens at the Field Museum. Among the specimens was a hatchling raptor that was picked up alive, but underweight and in poor health, by Willowbrook volunteer Hans Lim on July 22 in Mt. Prospect, in northwest Cook County. Despite Willowbrook's efforts, the bird didn't survive. The bird was so young that it still had some of its natal down and its primaries were not fully grown, indicating that it couldn't fly, or at least couldn't fly far. The bird, understandably, was originally thought to be a Broad-winged Hawk (Buteo platypterus), a local and uncommon breeding species in northeast Illinois, but not unheard of. It's a species that we infrequently add to the collection, averaging fewer than one per year from Illinois over the last decade (almost all of which came to us from Willowbrook). Even rarer is getting such a young bird, even though all birds, raptors included, have high rates of mortality in their first year of life.
Because of the specimen's rarity, we prioritized it for preparation. As I walked through the prep lab on Wednesday, I saw it sitting out, waiting for Tom Gnoske to prepare it as a study skin. But it immediately struck me as off for a Broad-winged Hawk. Upon closer inspection, I realized it was a Merlin!
Merlin (Falco columbarius) is a small falcon that typically breeds in the boreal forests well to our north and has never before been confirmed nesting in Illinois. However, they have been seen a few times in summer in the state in recent years and they've been expanding their breeding range south in recent decades. Over that same period of time, much like Cooper's Hawk and Peregrine Falcon, they have been adapting to urban landscapes. Many birders predicted that it wouldn't be long before Merlins were confirmed breeding in Illinois, and it has finally happened. In the 2013 volume of the Illinois state ornithological journal, Meadowlark, Steven D. Bailey discussed this very scenario:
One species that appears to have Illinois in its crosshairs for expanding its breeding range southward is the boreal-nesting Merlin...This year , two Merlins were well-documented with photos, both in July, and one as far south as central Illinois. As I write this, a female and two juvenile Merlins have been discovered at Pokogan State Park in Indiana near its border with Michigan, likely representing that state’s first nesting record. Merlins showed the largest increase in population in a recent study group of boreal-nesting bird species (Niven et al. 2004), and the species has made a fairly rapid movement into urban and suburban city breeding locales over a large part of their range relatively recently (Warkentin et al. 2005), including agricultural and urban areas of nearby Wisconsin (Cutright et al. 2006). In Ontario, Canada, only one urban nesting Merlin was found during their first breeding bird atlas project in 1986, but by the time their next atlas project was completed in 2006, the Merlin had become the most common breeding raptor in some Ontario cities, including Ottawa (Cadman et al. 2007). Illinois birders should be on the lookout for nesting Merlins in the years to come. They don’t build their own nests but often choose old American Crow (and so also likely old Cooper’s Hawk nests), often near water, especially wetlands.
Merlins have become more common in winter in Illinois, as well, and no doubt they will be found nesting again in our state. In Massachusetts, for example, Merlin was first found nesting in 2008, and has since become a regular breeding species there. In the case of the Mt. Prospect nest, just one young bird was found on the ground. Given that the average number of chicks per nest is 3.5-4 (Sodhi et al. 2005), we can hope its siblings survived and will come back to breed in the area next year.
Thanks to Hans Lim for providing photos of the bird and details about the circumstances around picking it up, Ron Skleney for providing additional details, and John Picken for providing the banner image.
Bailey, S.D. 2013. Field Notes: The 2012 Breeding Season. Meadowlark: A Journal of Illinois Birds. 22: 9-44.
Cadman, M.D., D.A.Sutherland, G.G. Beck, D. LePage, and A.R. Couturier (eds.). 2007. Atlas of the Breeding Birds of Ontario, 2001-2005. Toronto: Birds Studies Canada et al. 706 pp.
Cutright, N.J., B.R. Harriman, and R.W. Howe (eds.). 2006. Atlas of the breeding birds of Wisconsin. Madison: Wisconsin Society for Ornithology. 602 pp.
Niven, D.K., J.R. Sauer, G.S. Butcher, and W.A. Link. 2004. Christmas Bird Count provides insights into population chance in land birds that breeed in the boreal forest. American Birds. 58: 10-20.
Warkentin, I.G., N.S. Sodhi, R.H.M. Espie, A.F. Poole, L.W. Oliphant, and P.C. James. 2005. Merlin (Falco columbarius). The Birds of North America (P.R. Rodewald, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from The Birds of North America: https://birdsna.org/Species-Account/bna/species/merlin/ DOI: 10.2173/bna.44