late warblers in CO

[DAVID A LEATHERMAN]

By my count, Colorado has hosted at least 19 species of warblers since November 1st.  I probably missed one or two.  The list jotted down includes (in no particular order):

prothonotary

black-and-white

northern parula

yellow-rumped

chestnut-sided

yellow-throated

pine

Nashville

Townsend's

common yellowthroat

black-throated blue

ovenbird

blackpoll (not sure if this one was ever confirmed)

yellow

Tennessee

MacGillivray's

Wilson's

orange-crowned

northern waterthrush

I think the key foods involved are aphids, midges and suet.  Fruit on trees like juniper, Russian-olive, viburnums, mountain-ash and crabapple are probably also part of how these birds can cope with cold weather, fatten up and hopefully move on.

Any species I missed?  How many will brighten our Christmas Counts?

Dave Leatherman

Fort Collins

[DAVID A LEATHERMAN]

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

[Marty W]

Thank you as always, Dave Leatherman! I (and so many) always love your observations, photos, explanations & information, and especially (as here) your musings & speculations (based as they are on science and an experienced, open & inquiring mind)!! Always sharp & insightful.

Marty Wolf

NW CO Spgs

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[Todd Deininger]

Palm Warbler, Nov 13, 2011 Boulder City 

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[Willem van Vliet]

Great questions!  Christiaan Both (Groningen University) has been examining some of them. See, for example: https://research.rug.nl/en/publications/climate-change-breeding-date-and-nestling-diet-how-temperature-di 

Willem

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[Kathy Palouti]

Owl on the Roan Plateau north of DeBeque. Looks like a flam to me. 

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[DAVID A LEATHERMAN]

Two additions (hooded and bay-breasted) bring the total species of warblers in CO since November 1, 2022 to 23.  That is pretty remarkable.  "Misses" (with a small "m") from the 2022 list would seem to be palm and blackburnian, as they have occurred more than once late in previous years.

Dave Leatherman

Fort Collins

[Peter Burke]

Dave,

As if you willed it, a Palm Warbler was reported from a private residence in Boulder County this morning.

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Best,

Peter Burke