[cobirds] late warblers in CO

Kudos to Lori Z. in Fort Collins for finding a very late Northern Waterthrush along the Poudre which was warbler species #19 on my draft list for CO since November 1, 2022.  Brandon and Tyler have added Cape May and American Redstart, respectively, for a total so far of 21.  People fluent in eBird archives can probably find a palm record for CO since November 1 and I seem to recall a bay-breasted in nw CO (or was that October?).  

Whatever the total is, it's almost as good as what we get during the supposed "primetimes" of late May and September.  And I'd love to know the reason for the late flush of these individuals that "didn't get the memo" about when it's best to migrate.  Are they mostly first-time migrants (i.e. young born last summer) from late-starting first or second nests?  Are they just not wired correctly?  Are the late adults we see individuals that didn't nest at all, or that had failed nests, late nests, or what?  I was sent a NYT article that makes the case for various species of forest rodents that feed on forest tree seeds in Maine having different personalities.  Why not birds?  Are some birds simply procrastinators?  Are more late migrants these days surviving than would have been the case "in the old days" because current late autumn weather tends to be milder?  Do they pass on this timing to their offspring next summer?  Is a proliferation of urban plantings that support the kind of foods needed to pull off a late migration part of it?  Maybe it just seems like there are more late migrants because more of us are looking than used to be the case (see David Suddjian's recent graphs of increasing eBird checklists).  Lots of questions begging answers. 

Dave Leatherman

Fort Collins