An unfortunate scene played out last Saturday morning at a crowded bird feeder in a front yard on County Road 22.
Invasive Eurasian collared doves bullied a feasting flock of red-winged blackbirds, pushing them away from an easy meal. The native mourning doves were nowhere to be found.
“Our native species is gone,” Fred Blackburn said. “We got a piece of crap here.”
The observation was made during the 119th annual National Audubon Society Christmas Bird Count in Cortez. It’s a long-running citizen science project that spans the Western Hemisphere. Volunteers count as many birds as possible in 15-mile diameter circles to track trends and species decline.
Blackburn, an amateur birder of 50 years and veteran Christmas Bird Count participant, teamed up with first-time Christmas counter Patricia McClenny, a retired social worker, to cover an area west of Cortez. The scene they encountered at the bird feeder is indicative of long-term trends observed during the Cortez Christmas Bird Count since 1990.
Jason St. Pierre, a biologist who has organized the Cortez count for four years, said Eurasian collared doves were nowhere to be found in the early 1990s in Colorado. There was a lapse in local bird count data from 1994 to 2006, but then in 2007 birders in Cortez counted 148 of the invasive doves. A total of 2,832 have been counted in Cortez over the past 12 years.
“They’re pretty aggressive,” St. Pierre said. “They are competitors with mourning doves, it seems like.”
According to statewide Christmas Bird Count data, Eurasian collared doves were first observed in Colorado in 1996. Eight were counted that year. Their numbers ballooned to 13,600 in 2010, 22,300 in 2014 and 14,000 last year.
The native mourning doves, meanwhile, have rarely been seen in the winter. Just 52 have been counted since 1992 in the Cortez count. Statewide data suggest mourning doves peaked in the mid-2000s, with 4,300 in 2005. Numbers were down to 2,000 in 2013, and to 1,070 in 2017.
After slowly cruising around county roads and hiking through knee-deep snow at Hovenweep National Monument, Blackburn determined it was a low-count day for his group. They saw plenty of red-tailed hawks, ravens, horned larks, magpies and Northern flicker woodpeckers but the team noticed a shortage of pinyon jays.
“OK, pinyon trees, start producing us some birds,” Blackburn said during a mid-morning lull.
He said the drought has possibly impacted the pinyon jay. As pinyon pines have died off, the pinyon jay has likely struggled to find food.
The 20 participants involved in the Cortez count recorded 32 pinyon jay sightings, down from 65 in 2016 and 57 in 2017, but a massive increase from the zero pinyon jays counted from 2012 to 2015.
St. Pierre said that’s common behavior for an eruptive species like the pinyon jay. He said they are a mobile species that travels wherever it can to find food. Finches act in a similar manner. He said the shift from zero birds one year to dozens the next doesn’t necessarily mean the species is in decline.
“One year might be a really good crop for whatever seed these species are eating, and the next year they have to go somewhere else to find it,” St. Pierre said.
That’s an important aspect to keep in mind when analyzing Christmas Bird Count data, St. Pierre said. He said it’s difficult to make inferences based on one year of data, and the Christmas Bird Count is all about the long game. It might be particularly cold one year, or maybe a large number of bird-watchers volunteered count one year, skewing the data.
“The long-term trend is what we’re looking for,” St. Pierre said. “Birds are good environmental indicators, perhaps the best, because they are transient.”
Based on the last several years of data, St. Pierre said record-breaking numbers of certain species in the area could signal environmental and climate changes. This year, volunteers recorded high numbers of Northern shovelers, sharp-shinned hawks, white-crowned sparrows, Western bluebirds, cedar waxwings, yellow-rumped warblers, song sparrows and spotted towhees.
“Their range is expanding northward in the winter because the winters are becoming more mild,” St. Pierre said.
The 20 volunteers also spotted two new species that have never been observed during the local Christmas Bird Count: a peregrine falcon and a green-tailed towhee. The entire group spotted 7,048 birds from 77 species.
Depending on what part of town the volunteers covered, they came to different conclusions. Blackburn said his group had a low-count day, but Diane Cherbak, who patrolled north of Cortez, said her group was pleasantly surprised.
They started off with low expectations because of the cold weather — it was zero degrees when the groups departed from the Cortez Cultural Center at 8 a.m. — but they were able to spot some uncommon snow geese, a merlin and a Wilson’s snipe shorebird. Cherbak said she’s attended the Christmas Bird Count for nine years now.
“There’s a camaraderie of the same people who come back every year,” Cherbak said. “It’s a citizen science project so you just get enthused about wanting to contribute, do your part.”
Blackburn said birding is a lifelong activity that anyone can pursue. Spotting a species for the first time, he said, provides a sense of discovery that keeps you coming back for more. There’s also a healthy dose of science.
“Anything with birding and counting is monitoring species decline, increases,” Blackburn said. “The way it’s done over many, many years – you can really see the trends.”