Kestrels should definitely not be breeding at this time in Massachusetts. In fact, many of the birds present in November may be migrants from farther north. I couldn’t find anything specific on Mass. on the web, but from breeding dates in other states I wouldn’t expect them to begin breeding before April, and more likely May.
I don’t know offhand if American Kestrels do the kind of aerial display described. I’ll see if I can find something out. However, the antifreeze hypothesis seems to be the best one to me. I wouldn’t completely rule out Kestrels scavenging a roadkill, but I’ve never seen one do that and I doubt it is regular behavior.
PS. As far as I recall, the only birds that copulate in flight are swifts.
I am leaning toward the antifreeze hypothesis as well.
Am I right in thinking that birds that do the free fall aerial behavior would only do it during the breeding season?
If yes, the time of year would seem to eliminate that possibility in this particular case.
BTW, screech-owl, if I wasn’t clear earlier, the thing about the GHO’s breeding up here in January I am pretty sure about. I have read it several times, usually in the Boston Globe’s Nature columns. I think I have also heard it from the Mass. Audubon Society. So, we still have a few months to go. I believe they are resident up here all winter, though. Fascinating birds.
The antifreeze idea may well be it. To expand a bit on my previous post [way up top], say someone puts out poison to kill a target species, but puts the wrong concentration or doesn’t otherwise follow instructions to prevent non-targets from getting whacked. Poison put out for coyotes in the west improperly leaves a poison-ridden carcass, which eagles go for and die in turn, for example. That’s why concentrations and types are specific, as are methods [like hiding the bait so the carcass is unavailable later…]
As you’re talking about Massachusetts, anti-freeze prior to the winter season is one idea, as is overly robust applications of pesticide in light of recent West Nile virus spread… puddle of insecticide ? insecticide ridden rodent ? etc…
More likely in the very, very beginning of the breeding season: it’s a pre-copulation ritual, like some birds bow and cheep to each other. As another example, some hawks** partake in a ritual ‘passing of food’ (male flies with a critter in talons, female flies up to male, flips upside-down as the male drops the food into her claws, and she flies to a branch and eats). This re-establishes the pair-bond, or kind of an extensive ‘avian foreplay’. After the eggs are laid, there is not a lot of time for bonding, since the eggs must be turned and kept warm by one parent while the other hunts for food (both for itself and the incubating mate). After the chicks hatch, there is even less time, since one parent is hunting for the whole family (itself, the mate at the nest and the new chicks - in some species, both parents alternate with the brooding and hunting); later both parents will hunt and teach the young one to hunt on its own. So there is not a lot of time for the parents to free-fall while they have family responsibilities.
Not all species of birds engage in such rituals nor stay with one mate for the season or a lifetime: Red-winged Blackbirds, shall we say, copulate at the drop of a feather with darned near any females in the area, and often the females must brood the chicks and do their own hunting.
Others are more into the extended family : Florida Scrub-jays raise the chicks and do kick them out when the parents are ready to raise the next batch, but the first batch of kids settle in an area near the parents and help the parents raise the next brood (brooding the chicks, hunting, and guarding the nest) while raising their own chicks, so there is an extensive family of aunts and uncles hovering about, continuing with each successive generation.
**IIRC, the red-shoulder - I’d have to check my ref book again.