Date: 6/1/18 6:47 am From: Childs, Jackson <jchilds...> Subject: RE: [MASSBIRD] Bay-breasted, Harvard Yard/crazy Quebec report
Thank you for your comments. I think you are right there is a confluence of date, weather, geography. I’ve also suspected that migration gets to be more precise or condensed as birds get closer to their destination: a species tends to hit a breeding area almost all on the same day, given the competition for territory (probably there are papers on this, so sorry if this is amateurish speculation). So the numbers counted may be a substantial percentage of the population of those species for that region. Also, I understand there has been a spruce budworm outbreak in just that region of Quebec in recent years, although I don’t know what the status is of that this year.
It’s right on the shore of the Saint Lawrence River, which runs more or less from the Great Lakes near its west end to the Atlantic on its east. North of there is a huge area which is, as far as I can tell, overwhelmingly unpopulated and undeveloped. The acreage appears to be larger than the combined total of all of New England, New York, Pennsylvania, Nova Scotia, and New Brunswick, combined; but without most of the cities, highways, sprawl, fragmentation, etc. So I think the phenomenon is one where the weather (Ian comments about the wind direction and rain in his eBird report) and geography bottlenecked, in both space and time, the breeding bird population of a really large and healthy ecosystem. The only other similarly large and healthy ecosystems are further west in Canada and Alaska, and have mostly land south of them without any really large bodies of water, so the migrants headed there can spread out over much wider areas on their way north.
That’s my hypothesis anyway. Maybe Ian himself will weigh in on the topic, after he catches up on his sleep, which might be in November or so knowing him.
As for your lack of Cape Mays, I’ve managed to miss both that *and* Bay-breasted, and Mourning too, not just this year but pretty much entirely since I left Texas and moved back to Massachusetts. Not that I’ve made concerted efforts to target those species, but I’ve seen 27 other warbler species in the state during the same span of time, you’d think I’d have blundered into one or two of that trio by now. I’d worry that my hearing was declining, but I’m not having any trouble hearing Black-and-Whites, Blackpolls, or Brown Creepers as far as I can tell… yet…