Date: 5/6/25 9:21 am From: <chucao...> Subject: RE: [MBBIRDS] This year's migration numbers/lateness
Pete
It is a new outlier, a new normal would only be a “norm” once we have multiple outliers like this to create a pattern. We are not there yet, so it is an outlier.
Fires/birds/migration – keep in mind that the Western (Pacific) migration system is complex with many species having a huge latitudinal range. Often much greater latitudinal ranges than birds out East. As such, migration is super protracted. We can see Wilson’s Warblers as early as March and as late as late May moving north. The earlier migrants are the ones that breed farther south, the later migrants the ones that breed farther north. So it is very difficult to sort out what sector of the breeding range is affecting migration numbers, if there has been a disruption there, and this is separate from the fact that these different latitudinal breeding areas often have a different section of the world where they go to winter. In short, it is way to complex to make sense of it. But when we see some major shift like this year, something major must have happened. Not a gradual incremental type change, or even trend over time. Keep in mind that small birds can recoup a population rather quickly if all systems are go when they breed (for example the spruce budworm species of warblers in the north/east).
From: Pete Sole <pete...>
Sent: Tuesday, May 6, 2025 8:49 AM
To: Jane Mio <jmio...>; <chucao...>
Cc: Abram Fleishman <abfleishman...>; Carol Pecot <carol.pecot...>; MBB <mbbirds...>
Subject: Re: [MBBIRDS] This year's migration numbers/lateness
Hi Jane,
Interesting question, I don't have any insight on the fires. The most hopeful response I can come up with, is that maybe the fires open up different ecological niches for less common birds. But I have no data to back that up.
Alvaro,
Thanks for the insight. I guess the one big question is whether the pattern we are seeing this year is an outlier, rather than a "new normal" of sorts. In my own yard, all of the expected regular breeding migrants have appeared or passed through, but the numbers are lower. Specifically, Black-headed Grosbeaks and Western Flycatchers are sparser.
My hope is that this year is very much an outlier, with higher numbers of migrants and the resumption of earlier arrivals in the coming years. But time will tell.
Pete
On 5/5/25 12:37 PM, Jane Mio wrote:
Does anybody have info of the various wildfires impacts on migratory/local breeding grounds?
Some of the fires took place smack in their habitat during the nesting season.
BTW: I, too, have noticed that my neighborhood is mighty bird silent this spring & the usual migratory species are either absent or sparse.
I think that one has to step back and realize that there is variation year to year as you all mention and that is normal. But, what has been noted this year is far from the norm. People who have been birding for a long time, and have a good gut feel about bird arrivals and migration density suggest it is way, way off the norm this year. Both late and low volume. I have not been birding much this spring so it is what I am hearing from folks, more than what I am seeing. The suggestion is that very dry winter in parts of Mexico may have influenced overall numbers or health of birds down there. The suggestion is that many may have died. Of course with birds that only live 5-6 years, one good year can resupply the loss that can happen in a poor year. We shall see.
