This year’s season of ‘The Falcon Bachelor’ flipped the script! As usual, Newman passed out roses – by which we mean food gifts – to a succession of female falcons. We spotted Julie 90/Z (a regular visitor), Kandiyohi H/34, Hope E/60, and Newman’s mate from last year, Elaine U/09! Elaine celebrated her second birthday and first year as an adult this spring, and we were excited to see a little less drama than we saw last year. Or so we thought!
Real Falcon Housewives of the Mississippi River
US Bank to GSB: Five miles as the falcon flies
We have a nest box at the US Bank Building in La Crosse, Wisconsin, roughly five miles SE of Great Spirit Bluff as the falcon flies. Male Ardy 06/D, a 2015 hatch from Ardent Milling in Lake City, MN, has nested there with Karen 44/P, a 2016 hatch from MPL’s Clay Boswell plant in Cohasset, MN since at least 2021. We were quite surprised to see Elaine show up in Karen’s stead this spring. Or did she? For at least two weeks, Elaine flew back and forth between La Crosse and Great Spirit Bluff, chasing competitors away, receiving food gifts, and copulating with both males. Twice the courtships, twice the attention, and most importantly, twice the food gifts!
We’re usually wondering which falcon the irresistible Newman will end up with! But Elaine flipped the script by locking down two territories and two potential mates. Since she appeared to prefer Ardy – she certainly spent more time with him – we were wondering if Newman would end up with a mate at all. When Elaine laid an egg at US Bank La Crosse, we figured it was game over. Sorry, Newman! But Elaine confounded our expectations by laying her next four eggs at Great Spirit Bluff! As I write this…
- Elaine and Newman are in full incubation at Great Spirit Bluff. We expect hatch on or around May 5.
- Ardy is pursuing an unbanded two-year-old female. Addie isn’t caring for Elaine’s lone egg, but will probably lay her own.
- Elaine dropped by to visit US Bank on April 7 while Newman was busy incubating the couple’s eggs. She tussled with Addie, briefly chasing her away. Is she still locking down the territory and/or copulating with Ardy? We’d love to see how closely related the GSB nestlings are to one another, since Newman might not have fathered all of them!
April 7, 2025: Elaine visits US Bank. Addie disapproves. This is a more typical interaction than chilling together. Video: https://youtu.be/wEjOCnQU5_M?si=Qn8PQQEXp4Tf3-fb
Wait, How Common is This?
Polyterritoriality – a single bird using or defending multiple territories for nesting or resource access – appears to be pretty rare in peregrine falcons. Jackie Fallon from the Midwest Peregrine Society recorded it twice in St. Paul, MN, while Mary Hennen from the Chicago Peregrine Project hasn’t recorded it at all in Illinois. It’s a complicated question: this situation could also be referred to as polyandry (one female, multiple males) or extra pair paternity (what we call ‘cheating’). Formal polyandry (everyone is cool with it) is pretty uncommon, but genetic studies found that females mated with extra males in about 76% of 255 bird species that form socially monogamous pairs and raise young together. While the frequency varied across species and individuals, extra-pair young were found in roughly one-third of nests overall.
Elaine and her eggs. Did Newman father all of them?
Do raptors engage in complex mating behaviors? At one point, researchers might have pooh-poohed the idea. But a recent study found high rates of extra-pair paternity and conspecific brood parasitism in Cooper’s Hawks. Like Peregrine Falcons, Cooper’s Hawks are highly territorial, form what we thought were monogamous pairs, aren’t social or gregarious on or off their territories, and generally mate with the same partners every year. The study turns our knowledge of Cooper’s Hawks on its head and leaves us wondering what we don’t know about Peregrine Falcons. Is this behavior more common than we thought?
Interesting Year, Interesting Behaviors!
This isn’t the only Peregrine Falcon nestbox that left us scratching our heads this year! We documented two male falcons simultaneously courting a female falcon at Xcel Energy’s High Bridge nest box in St. Paul, MN and Bay Front nest box in Ashland, WI, two-year-old females at multiple nests (older, more experienced females are more likely to own and return to sites), and mate replacements at multiple sites. Are these normal things we didn’t document prior to HD cameras, widespread banding, and skilled monitors, behavioral changes driven by a growing, increasingly urbanized population, or signs of a scarcity of adults – especially adult female falcons?
The second ‘if‘ isn’t as far-fetched as it sounds. Urban Peregrine Falcons tend to be more tolerant of other falcons than we believed possible: Bald Eagles are nesting closer to one another and to us than we ever thought they would. They and many other species (Cooper’s Hawks and Branta canadensis maxima, for example) confounded our expectations and understanding when they moved into our world. Perhaps they’ve always adjusted their behavior based on ample food supplies, generational habituation, or some other factor: highly territorial and aggressive when food is scarce and the environment is dangerous, a little less so when food is plentiful and the environment is chill. Untangling the puzzle isn’t easy when large urban environments are so new, evolutionarily-speaking, and of course we don’t have many records before avian populations plummeted. How did they used to act before we changed everything? We don’t know.
TLDR: Maybe the two males simultaneously courting females were habitually chill. Why fight and die if you don’t need to? But that doesn’t explain the absence of a territorial female at the US Bank La Crosse nest box.
Highly Pathogenic Avian Influenza
Highly pathogenic avian influenza has all of us a little on edge. If adult female falcons have died in high enough numbers, it might explain why there wasn’t an occupying female at US Bank La Crosse to chase Elaine away. Extra-pair paternity isn’t likely to happen with a territorial falcon on site, right? It also might explain the increased presence of two-year-old birds at our nests. We look forward to talking with other banders and monitors about what they are seeing.
And in the meantime, go Elaine!
Resources
The Raptor Resource Project