I'm also quite curious if anyone has any thoughts on the underpinnings of this bouquet of eastern warblers that have been inhabiting Boulder Creek for the past few weeks. There have been 6 different species--Chestnut-sided, No. Parula, Tennessee, Pine, Orange-crowned & Nashville—holed up in this location for some time now. None of them choose to leave with this past weekend's cold snap into the low teens (which I expected likely would happen). We'll see what comes of today's snow storm.
But this has had me pondering how this group might of all come together. We're these birds all migrating together as a mixed flock and came to this location together due to the food resources they found here? Or did they separately get off course and stumble upon this Aphid-rich spot? Would such a coincidence be possible? All six of these birds are well out-of-range, considerably off their typical migration route, and quite delayed in their travels south. Are they sticking around so long because they can't get enough food and put on enough fat to fuel the next leg of their journey south or is the eating so good they just don't want to leave? Obviously, I know we likely cannot know with any real certainty how this came to be, but I'd love to hear what thoughts folks may have about gathering's origins.
John Malenich
Boulder, CO
John et al,I visited this area with friends on Black Friday. When in the trees, I think these insectivores are mostly getting APHIDS! Probably still a few alive but mostly I suspect the birds are getting cadavers. Aphids are high in sugars and would be highly sought after at this time of year for sustenance and migratory fuel. The birds might also be getting aphid predators like green and brown lacewings, maybe some midges when near the creek.
On a related note, the next "The Hungry Bird" article in press (published in "Colorado Birds", the publication of the Colorado Field Ornithologists) is about painted maple aphids in one sugar maple in Fort Collins and the assortment of birds they attracted this fall.
Dave LeathermanFort Collins
From: cob...@googlegroups.com <cob...@googlegroups.com> on behalf of John Tumasonis <snake...@gmail.com>
Sent: Tuesday, December 2, 2025 3:20 PM
To: Colorado Birds <cob...@googlegroups.com>
Subject: [cobirds] Nashville warbler, Northern Parula, and Chestnut sided warbler....
All:I bit the bullet and decided to check out the warblers near Boulder High today (12-02-25). I found three of the five species reported near the 17th Street and bikeway intersection. Several other birders had seen 4 of 5 species, before I arrived there. Here are a few things I noted:
1) These warblers are keeping close in loose congregations - if you see one species, you'll probably see several others.
2) Nearby flocks of red-breasted nuthatches, juncos, house finches, and bushtits may or may not be associated with the warblers.
3) The warblers I saw a feeding at heights of 12 to 40 feet up in all different kinds of trees, such as, willows, ash, oak, and cottonwood.
4) Almost all the trees being foraged on had some leaves - either desiccated, or turning yellow to brown. Gleaning (something) from both leaves and branches.
5) The warblers don't just "disappear" - they are foraging on both sides of the creek and upslope into brush onto CU campus properties, and Boulder High properties. They are also moving up and down the creek drainage.
6) Reports suggest they are foraging at all times of day: 8, 9, 11, and 12 and afternoon at 3 and 4 pm. They appear very hungry and are always in motion.
If trying to take photos I would suggest 200 to 400 mm lens, with high burst speeds.
And then the big questions: Why are these birds congregating is this location at this time of year? Will they continue through the next cold front coming on Wednesday? And what the heck are they eating?
Thoughts?
John T (Tumasonis), Broomfield CO"I'm not a real birder. I only pretend to be one on CoBirds."
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