The 117th CBC in the Wyoming

Nineteen CBCs were conducted in Wyoming for the 117th Christmas Bird Count, and 82,924 birds of 104 species were recorded. The number of species typically ranges from 110 to 133, so CBC-117 was on the lower end of the spectrum.  This was likely partly explained by the severe weather in the western portion of the state, where they experienced one of the worst winters in recent memory.  Many CBCs were rescheduled (up to 3 times in Casper) due to inclement weather during the CBC period.

Casper had the highest number of species (63), followed by Story-Big Horn (60), Sheridan (57), and Cody (54).  The lowest number of species (23) was recorded at the Gillette CBC.  The greatest number of individual birds was recorded at Casper (10,682), Cody (10,626), and Riverton (9030), while the fewest were recorded at Jackson Hole (1474) and Crowheart (1486). Species with the highest combined counts included Canada Goose (15,377), European Starling (14,536), House Sparrow (10,172), Eurasian Collared-Dove (4953) and Rock Pigeon (4561).  Introduced species accounted for 42% of all birds seen!

Unusual birds requiring CBC documentation included two Marsh Wrens at Bates Hole, a Cackling Goose at Guernsey-Fort Laramie, a Hooded Merganser at Lander, and a Mourning Dove at Story-Big Horn.  Other unusual birds included a Ross’s Goose at Green River and a Swamp Sparrow at Dubois.  This was the second straight year that a Swamp Sparrow was recorded on the Dubois CBC. Perhaps the biggest surprise of this year, however, was an African Collared-Dove at the Sheridan CBC. African Collared-Doves have recently been noted by astute observers among the Eurasian Collared-Doves along the Front Range of Colorado as well as in the Cheyenne area, and may be more common than once believed.  Birders in Wyoming should familiarize themselves with the slightly different plumages – but drastically different songs – of these two species.

Nineteen species occurred only on one count, while four species were recorded on all 19 CBC circles, including Mallard, Eurasian Collared-Dove, House Finch, and House Sparrow.  Eurasian Collared-Doves are now common throughout Wyoming, with 4953 individuals recorded, including a high count of 932 at the Lander CBC! Despite the severe winter in much of the state, several species that typically migrate south lingered through the early winter; these included Blue-winged Teal, Eared Grebe, Sandhill Crane, Marsh Wren, American Pipit, Vesper Sparrow, Spotted Towhee, Brewer’s Blackbird, and Common Grackle. 

Some CBC compilers have expressed concern over declining numbers of Golden Eagles. The 103 Golden Eagles counted during the 117th CBC was only slightly higher than the 98 counted last year, and is well below the 16 year average (since 2000) of 153.  Another species of conservation concern, Greater Sage-Grouse, was observed only on the Bates Hole CBC last year, but was observed on the Cody and Jackson CBCs this year in addition to Bates Hole. The Evanston CBC typically has the highest count of any CBC circle, with a 36-year average of 305, but no Greater Sage-Grouse were observed there for the second year in a row.  Evanston CBC compiler Tim Gorman attributes the lack of sightings during the 117th CBC to the heavy snow cover and cold temperatures, which caused the grouse to move to inaccessible areas at higher elevations where the wind had blown areas free of snow.  One of the factors thought responsible for the decline of Greater Sage-Grouse is predation of eggs and chicks by Common Ravens.  I therefore thought it would be interesting to examine Common Raven population trends in Wyoming using CBC data.  As can be seen in the figure below, Common Raven populations have steadily increased over the last 25 years in Wyoming, presumably due to increased food availability associated with fragmented habitats and development.

The number of participants for the 117th CBC appeared to be higher than in previous years, with 355 participants statewide.  Counts with over 30 participants included Cody (41), Sheridan (35), Jackson Hole (33) and Casper (32).  However, kudos also is due to the five participants who managed to cover the Crowheart and Evanston CBC circles.  I would like to thank everyone who participated in the 117th 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.