The year of the Kentucky Warbler
Luke Pheneger
Hi all,
Did you find yourself noticing Kentucky Warblers on Colorado rare bird alerts more often this spring? Compared to most years, the species seems to have had a remarkable showing statewide. This spring migration, there were 9(!) Kentucky Warblers found in 8 different counties, with 3 representing first county records.
I made a list of the total number of observations for every warbler species (and vireo) recorded in Colorado (see the bottom of this post). This is just a quick list of total eBird observations which does not count for inflated numbers and how easily chase-able certain records may have been. However; its impreciseness still provides a useful way to group species into broad rarity “tiers.” As you can see, Kentucky Warbler currently sits near the bottom of the list and is one of the rarest eastern warblers recorded in the state, numerically falling between Louisiana Waterthrush and Prairie Warbler. This year however, there have been more individual Kentucky Warblers in the state than Bay-Breasted, Blue-Winged, and Worm-Eating Combined. In fact, Colorado did not have a single confirmed Kentucky Warbler sighting in all of 2024 and 2025, and between 2020 and 2023 Colorado only had 9 total confirmed sightings.
This post is mainly to cast light on this event and is not meant to be investigative, but I will point out that this was not a particularly eventful spring migration for some other South Eastern United States breeding warblers such as Hooded (Brandon Percival exemption), Worm Eating, Prothonotary, and Prairie. This however, was an extraordinary year for Northern Parula, Louisiana Waterthrush, and White Eyed Vireo, so I’d go out on a limb to suspect there is some connection on that end. The number of observations of Louisiana Waterthrush is particularly over inflated due to two individuals being very easily chaseable within two heavily populated areas, but three in one year in our state is still exceptional.
I didn’t conduct any formal statistical analysis to determine whether these other warblers had a particularly good or bad migration this year. I’m mostly going off my own field experience and nightly scans of the rare bird alert, so I am excited to hear about the field experiences from other birders. Personally, I was lucky enough to see three Kentucky Warblers this spring, one of which was thanks to Dan Z and Leslie S in Boulder County. I had seen 2 total in Colorado before that.
Whatever the reason for this year’s influx, it was certainly fun, and I’m grateful to have gotten to bear witness to a fraction of it. Moments like this are a reminder that no matter how long you’ve been birding, migration is still full of surprises.
Number of ebird Observations in Colorado:
Warblers:
Yellow-rumped Warbler — 196,600
Yellow Warbler — 190,000
Wilson’s Warbler — 67,900
Common Yellowthroat: 56,300
Orange Crowned Warbler-48,500
Macgilivrays Warbler- 31,800
Virginia’s Warbler — 25,000
Townsends Warbler: 8341
Black-throated Gray Warbler — 8436
American Redstart — 6657
Northern Waterthrush — 5578
Ovenbird — 4807
Northern Parula — 3175
Grace’s Warbler — 2776
Nashville Warbler — 2511
Black-and-white Warbler — 2,085
Blackpoll Warbler — 1800
Chestnut-sided Warbler — 1613
Tennessee Warbler — 1451
Hooded Warbler — 1373
Palm Warbler: 1231
Black-throated Blue Warbler — 1163
Magnolia Warbler — 1004
Yellow-throated Warbler — 969
Pine Warbler- 885
Lucy’s Warbler- 693
Blue Winged Warbler- 486
Golden Winged Warbler- 476
Blackburnian Warbler — 428
Black-throated Green Warbler — 420
Cape May Warbler: 404
Bay-breasted Warbler — 403
Worm-eating Warbler — 334
Mourning Warbler — 318
Prairie Warbler: 301
Kentucky Warbler — 291
Louisiana Waterthrush — 267
Canada Warbler — 203
Hermit Warbler — 101
Golden-crowned Warbler — 92
Painted Redstart: 73
Swainson’s Warbler — 28
Connecticut Warbler: 26
Tropical Parula — 14
Cerulean Warbler — 7
Red-faced Warbler — 5
Vireos
Western Warbling Vireo — 65,500
Plumbeous Vireo — 32,200
Red Eyed Vireo: 4,678
Cassin’s Vireo — 3,239
Gray Vireo-3018
Eastern Warbling Vireo — 2,360
Bell’s Vireo- 1042
White-eyed Vireo — 889
Yellow-throated Vireo — 720
Philadelphia Vireo — 364
Blue-headed Vireo — 265
Yellow-green Vireo — 1
Photo by Brian Genge:
Good birding,
Luke Pheneger