Friday 25 June 2021

[cobirds] A report on Guanella Pass BBS route June 22, sign of the (bad) times?

One of my Breeding Bird Survey (BBS) routes is Guanella Pass, beginning above Georgetown in Clear Creek and proceeding along the Guanella Pass Scenic Byway over the pass and down to Grant in Park County, and then up Park CR 60 to its end in the upper watershed of the North Fork of the South Platte. BBS routes have 50 stops along a 24.5 mile route, with 3 minute samples collected at each stop once each year.

I ran the Guanella Pass BBS route on June 22 this year, normal timing, with good weather conditions. It was the easiest ever because there were so few birds! The total species I detected was just 29, the lowest ever for the route and down from the 5 year avg of 46 species. The total number of individual birds was just 127, the lowest ever for the route, just 33% of the 5 year avg of 387 individuals. I detected no species at all on10 stops. It is highly unusual to record zero species during a 3 min. BBS sample when weather conditions are reasonable. In fact, barring stops with really loud water noise, I have never had zeros on a BBS stop, but 10 on this survey?!

19 Species that are expected on the route (i.e., found in 3-5 of the last 5 years) were missed entirely. A number of these misses are species which were found in every year in recent history, such as Dusky Flycatcher, Steller's Jay, Red-breasted Nuthatch, Mountain Bluebird, Townesend's Solitaire, Pine Siskin, and Song Sparrow. Of the 29 species found, 15 species were found in numbers 50% or less than the recent 5-year avg. This included all of the species that form the core of the species assemblage of the route except for Warbling Vireo and Wilson's Warbler, which were the only core migrant species in near average numbers  this year. Spruce-fir forest and the alpine tundra near the Pass were the habitats that were the most empty of bird song. 

** A summary of missed species and those in low numbers is pasted below.

I haven't looked in detail at my other routes, but of the 4 others I've aready run all had notable low counts of many landbirds and more than the normal frequency of "missing" species. 

David Suddjian
Ken Caryl Valley
Littleton, CO

% of 
Species 5 yr avg
Broad-tailed Hummingbird 22%
Red-tailed Hawk Miss
Red-naped Sapsucker Miss
Hammond's Flycatcher Miss
Dusky Flycatcher Miss
Cordilleran Flycatcher 29%
Canada Jay Miss
Steller's Jay Miss
Clark's Nutcracker Miss
Common Raven 22%
Violet-green Swallow 31%
Mountain Chickadee 20%
Red-breasted Nuthatch Miss
House Wren Miss
American Dipper Miss
Golden-crowned Kinglet Miss
Ruby-crowned Kinglet 24%
Mountain Bluebird Miss
Townsend's Solitaire Miss
Veery Miss
Swainson's Thrush Miss
Hermit Thrush 16%
American Robin 50%
Pine Grosbeak Miss
Red Crossbill Miss
Pine Siskin Miss
Fox Sparrow 16%
Gray-headed Junco 36%
White-crowned Sparrow 16%
Song Sparrow Miss
Lincoln's Sparrow 48%
Green-tailed Towhee 42%
MacGillivray's Warbler 50%
Audubon's Warbler 32%
Total Species 64%
Total individuals 33%

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