The 118th CBC in Wyoming

Nineteen CBCs were conducted in Wyoming for the 118th Christmas Bird Count, and 90,079 birds of 116 species were recorded. The number of species typically ranges from 110 to 133, so CBC-118 was somewhat in the lower end of the spectrum.  

Casper had the highest number of species (69), followed by Jackson (59), Story-Big Horn (58), and three count circles each with 53 species (Sheridan, Riverton, and Cody).  The lowest number of species (26) was recorded at the Gillette CBC, followed by Sundance (30) and Green River (31).  The greatest number of individual birds was recorded at Story-Bighorn (15,247), Casper (11,961), and Riverton (10,012), while the fewest were recorded at Gillette (1393), Pinedale (1587) and Sundance (1594). Species with the highest combined counts included Canada Goose (21,905), European Starling (12,869), House Sparrow (7209), Rock Pigeon (5418), Eurasian Collared-Dove (4781) and Bohemian waxwing (4220).

For the second year in a row, an African Collared-Dove was observed on a Wyoming CBC, this time in Lander.  The previous one was observed last year in Sheridan.  Other unusual species included a Winter Wren at the Lander CBC, and Brewer’s Blackbird, Great-tailed Grackle, Black Rosy-Finch, and Harris’s Sparrow at Laramie. There was a large influx of Bohemian Waxwings in the state, with 4220 individuals counted across nine count circles.  Story-Bighorn had the highest number, with 2695 individuals!   

Twenty-six species occurred only on one count, while four species were recorded on all 19 CBC circles, including Mallard, Eurasian Collared-Dove, Black-Billed Magpie, and Townsend’s Solitaire. The 2017/2018 winter in Wyoming was not as severe as during the previous year,  and several species that typically migrate south lingered through the early winter, including Ruddy Duck, Horned Grebe, Western Grebe, American Coot, Sandhill Crane, Killdeer, California Gull, Marsh Wren, House Wren, Mountain Bluebird, Green-tailed and Spotted towhees, Great-tailed and Common grackle, and Brown-Headed Cowbird.  Weather was fairly typical for early winter during most of the counts, although temperatures ranged from -6 to 10 degrees F during the Cody count and from -10 to 5 degrees F during the Story-Bighorn count.  The strangest weather occurred during the Cheyenne CBC on 12/30/17.  It was fairly calm with a temperature of 7 degrees F at the start of the count, but a Chinook wind began in the afternoon, and the temperature jumped to 56 degrees F with 40 mph winds!

The House Sparrow has undergone a significant decline in its native Europe, where populations were down over 60% from 1994 to 2004.  Similar declines have been noted in North America, with up to 90% declines in eastern Canada and a 62% decline in Philadelphia since the 1960’s.  House Sparrow declines also have recently been discussed on the Colorado Birds list serve. At first glance, a reduction in House Sparrow populations would not be of concern due to their impacts on native species.  However, the cause of the decline isn’t known, and some feel that whatever is causing their decline could start affecting native species as well.  Out of curiosity, I plotted House Sparrow abundance from CBC data for the entire state of Wyoming over the last 20 years.  The results do seem to indicate a slight decline of House Sparrows in Wyoming over this time period as shown below, with the lowest number per party-hour over the last 20 years occurring during the 118th CBC.

The number of participants for the 118th CBC was very high, with 385 participants in the field and 92 feeder watchers statewide.  Jackson Hole had the highest number of participants in the field, with 62, while Casper and Sheridan each had 32 field participants. However, kudos also is due to the four participants who managed to cover the Sundance CBC circle.  I would like to thank everyone who participated in the 118th CBC in Wyoming, as well as the compilers and observers for submitting rare bird documentation forms for the unusual birds observed on Wyoming CBCs this year.