Date: 11/29/19 2:59 pm From: LARRY ARNOLD <larnold47...> [ible] <ible-noreply...> Subject: [IBLE] Re: migration and irruption
IBLE, with cc's to people otherwise unable to receive ~~~~~ ?
I don't remember responding to Carl's note below....... maybe yes in my dreams?
Carl provides excellent discussion, and I've gotta say that migration in all of its "formats" has long been one of my topmost two or three favorite subjects regarding birds, and Peter Berthold's "General Survey" (2001, maybe since updated?) (Oxford Ornithology Series) has been one of my favorite references on topic. I can offer only conjectures, e.g., that "irruptive species" utilize irruption as a precondition to range expansion in a manner similar to "vagrant species" that are doing the same thing but at a slower pace.. As an example, some warbler species tend to wander out of their expected ranges much more often than others do, and looking back at state-level CBC data I can see that ECDO are expanding northward way faster than WWDO, yada yada et yada. I've often thought of out-of-range birds as genetic outliers that are necessary for a given species' adaptive survival in a universe that is continually changing, whether they be considered as "typical migrants" or not. And I've not often considered "irruption" to be a black-and-white phenomenon for this or that species, vs. not for other species where it is much more subtle. Does this make sense? Seems to me there is a "spectrum" of "irruption" with some species being far less obvious at it than others....?
Maybe somebody can provide clarity, or reference to published data re "migration and propensity toward irruption" as it might relate to genetic variability. But I can't imagine what such "data" might look like.
Thank you, Carl, 10^6 for your discussion below. Love it !! =)
W Boise / Garden City
From: "Carl Lundblad <carl.lundblad...> [ible]" <ible-noreply...>
Cc: "IBLE" <ible...>
Sent: Friday, November 15, 2019 9:28:37 AM
Subject: Re: [IBLE] And Then There Were...Three
Blue Jays move (presumably mostly out of Alberta) into (mostly north) Idaho each year in the fall. Some years it's a few. Some years it's a lot. This year happens to be a banner year with large numbers arriving throughout Idaho, including in more places than usual, and some making it as far south as northern Nevada, Utah, and southern Wyoming (below which they bump up against the breeding population on the Front Range). Montana is complicated because they have a breeding population (and some of our winter birds may come from there), but they also receive an influx during fall and winter. They are undoubtedly attracted to and facilitated by feeders and urbanization. While there may have been a slow range expansion over the last quarter century, this is much more a case of year-to-year variation in an irruptive species than a directional trend. Most or all of them will leave in the spring, although it wouldn't be surprising if a few eventually began breeding in Idaho (probably initially following with a big irruption year, like this).
Since sunrise this morning, I've been watching 3 Blue Jays coming in to feed on both whole corn kernels & black-oil sunflower seeds. Oftentimes, with all 3 present at once.
Given the reports this fall of Blue Jays, esp in E ID, I pulled my records. My only Steller's Jay sighting at our place along the Snake River was 10/8/2000, feeding in our dry overflow channel. First Blue Jay sighting was 5/16/2012 at the feeder. Then, last year, the one which overwintered, arrived on 10/21/2018 to the feeder.
Makes for some interesting questions. Are we witnessing a fall irruption of Blue Jays? Or, do we have a front row seat to observing the range expansion of Blue Jays? Is providing a seed source through feeders aiding a range expansion? Would be interested in others' thoughts. Probably too early to draw firm conclusions, but interesting, nonetheless.
My 3rd generation farmer buddy tells me his mom, who was a hobby birder used to see the occasional Blue Jay years ago, at the family homestead, a mile directly west of me. And, as an aside, until Starlings showed, Mt Bluebirds would nest all through this area...even in their mailbox once! The mailman had them nail a box up nearby, so as not to disturb the bluebirds. That would have been in the 1960's. A lot has changed since then.