Re: [cobirds] Early migrants, random comments

Interesting observations, Dave. Thank you. I better get my hummer feeders up. I think two other factors in increased early seasonal reports of migrant species is the gigantic increase in the number of Colorado birders in the last decade or more, and the correspondingly huge increase in reporting of sightings, mostly a result of eBird despite its data quality challenges. Most of the early reports trigger the county filters, so hopefully the eBird review process helps insure some quality control there.

David Suddjian

Littleton, CO

On Tue, Apr 1, 2025 at 10:41 AM DAVID A LEATHERMAN <daleatherman@msn.com> wrote:

I remember Harold Holt's stab at defining migration windows for CO birds. Overwintering individuals of species that are overwhelmingly migratory made establishing true early dates difficult. Other factors involved in making statements about "early" observations are the new normals in light of climate change and the fact of Colorado's immense and diverse geography (altitudes and habitats).  Of late the eBird alert I receive seems full of legitimate, remarkably-early birds but is concurrently littered with apparently erroneous reports attributable to mistaken humans and/or the Merlin app. Wish there was a way to weed out the latter before they end up on alerts and certainly before becoming part of a database.

This spring, early reports of migratory warblers not normally part of the species subset that winter on occasion at feeders, seem remarkable. I know of a Northern Parula, Orange-crowned and Black-and-white that are solid reports, all in March.  Is the Lucy's reported in Yellowjacket Canyon a tad early?

All the swallows have been reported.  A Vermilion Fly almost as far north as WY at Rawhide.  

Regarding the expressed worry about these early birds surviving, cold is probably not the direct issue for them as much as adverse weather might be for their food (especially insects). Bernd Heinrich's field measurements of temperature outside and under the feathers of a Golden-crowned Kinglet in a Maine winter should be comforting to us rooting for bird wellbeing. 80-degree difference!  That is, -20 F air temp, +60 F at the skin.  (See: Heinrich, B. 2003. Overnighting of Golden-crowned Kinglet during winter. Wilson Bulletin 115:113-114).

Dave Leatherman

Fort Collins (currently in Lamar)

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