Ecostewards Track Changes in Distribution of Boulder County Wildlife

Since 2007, three-dozen Boulder County volunteer ecostewards have noted the distribution of birds, mammals, herps, and butterflies in more than 20 adopted areas. Most of these areas lie within protected open space or national forest lands, so long-term monitoring gives us the opportunity to track regional changes in wildlife populations.

Among bird populations, we've documented several new Boulder County nesting species, including Hooded Merganser, Black-chinned Hummingbird, Black Phoebe, Eastern Phoebe, and Marsh Wren. Some of these species have expanded their documented nesting range more than 100 miles northward, taking advantage of the burgeoning tree and shrub growth along the Front Range foothills and possibly, warming temperatures.

Some species appear to be expanding their range to slightly higher elevations. Black-headed Grosbeaks and Yellow Warblers now nest at up to 9000 feet west of Hessie, and Ovenbirds are cropping up in nearly all our major foothills canyons. Some of our aspen-dependent woodpeckers are becoming scarce in areas of the foothills where aspen die-off is occurring.

Swainson’s Hawk. Photo by Steve Jones.

Volunteers have also noted an increase in nesting Cooper's and Swainson's Hawks in urban areas and an apparent decline in numbers of nesting Grasshopper Sparrows and Lark Buntings in our remaining grassland fragments. We've also noted a decline in numbers of Dusky Grouse observations as recreational use of foothills trails increases. "Suburban" species such as Eurasian Collared-Dove, Bushtit, Cedar Waxwing, Common Grackle, and Blue Grosbeak seem to be having a particularly good time of it in Boulder County as urban areas and deciduous tree cover expand.

Mink at St. Vrain State Park. Photo by Carol Cushman.

Among mammals, Elk and Mink are clearly increasing, and we can safely say that River Otters are becoming re-established in Boulder County, with individuals frequently observed west of the Peak to Peak Highway and occasionally seen in St. Vrain Creek west of Longmont. No White-tailed Jackrabbits have been documented on the plains since 2007, suggesting that this species has been extirpated from our local grasslands. American Badgers may also be in trouble.

Ecostewards spend a minimum of 16 hours per year documenting nesting bird populations, mammals, and recreational use in their adopted areas. New volunteers are always welcome. We've scheduled introductory field orientation sessions this coming June 14 in Long Canyon and July 8 at Crescent Meadows. Contact Steve Jones if you'd like to become involved: curlewsj@comcast.net

2019 Highlights

Ann White Trail. Cathy Comstock saw Western Tiger, Pale, and Two-tailed Swallowtails; and Milbert's Tortoiseshells; along with unusually high numbers of Red Admirals.

Bear Canyon. Bill Gumbart just adopted this area and couldn't get started until July, but he already has located potential nesting territories of Cooper's and Red-tailed hawks.

Bluebell Canyon. Holden Maxfield confirmed fledged Red Crossbills here in 2019 and raised the potential nesting species total to 48. A singing Indigo Bunting was another highlight.

Boulder Reservoir. More than 30 volunteers helping out with monitoring of birds of special concern located two successful Northern Harrier nests, each of which fledged four young in July. Both our Osprey nests failed, but American Bittern productivity appeared pretty good, with five documented territories fledging several young.

Crescent Meadows. Jannet Jamison documented Wild Turkeys, Black-chinned Hummingbirds, a Northern Goshawk nest, territorial Red Crossbills, and fledged Black-headed Grosbeaks.

Hodgson-Harris Reservoir. Peter Ruprecht coordinated the breeding bird survey this past year, and it was the most successful one yet, documenting 55 potential nesting species, including Blue winged Teal, Sora, American Avocet, Spotted Sandpiper, Cedar Waxwing, and Yellow Headed Blackbird. The volunteers have now documented 142 bird species at Hodgson-Harris Reservoir.

Long Canyon. We documented territorial Dusky Grouse, Wild Turkeys, and Cooper's Hawks, but no Hermit Thrushes, for only the second time in 15 years. Scott Severs and Shelley Schlender saw a Black Bear and cub one July morning. We have now observed and photographed 66 butterfly species in this uniquely moist foothills canyon.

Meyers Gulch. Laura Osborn and other volunteers, with help from Boulder County Parks and Open Space staff, have documented 75 potential nesting birds here, including confirmed Dusky Grouse, Wild Turkey, Red-naped Sapsucker, Williamson's Sapsucker, Olive-sided Flycatcher, Western Bluebird, Mountain Bluebird, and Red Crossbill. Recent Ovenbird singing activity suggests they may eventually nest.

Picture Rock. Over 11 years, Linda Andes-Georges has documented 73 potential nesting bird species along this trail at Hall Ranch. The Black-throated Hummingbirds are moving into this area as well as into Meyers Gulch and several other adopted areas.

Sawhill Ponds. Paula Hansley documented 38 potential nesting species this past year, including successful Wood Ducks and Ospreys. Over 13 years, we've documented a total of 80 potential nesting species here.

Skunk Canyon. Dale Ball, Elaine Hill, and Maureen Lawry documented territorial Ovenbirds for the seventh consecutive year, along with a Golden Eagle and Cedar Waxwings. They've observed 69 potential nesting species during 13 years of surveys.

South Boulder Creek State Natural Area. Janet McLaughlin has now worked this area for 13 years, documenting 75 potential breeding bird species and a growing number of butterfly species. 2019 was a particularly good year for Monarchs and Buckeyes.

(Old) South Mesa Trail. Bay Roberts observed pairs of Golden Eagles and Peregrine Falcons this year, along with Bushtits, Blue-Grey Gnatcatchers, Canyon Wrens, and Red Crossbills. A strong Ponderosa Pine cone crop is contributing to lots of breeding bird diversity.

Teller Lakes. After 13 years of working this area, Ruth Carol and Glenn Cushman are having to pass it on to someone else, since they are in the process of moving. Over the years they've documented 50 breeding bird species including Wood Duck, Blue-winged, Cinnamon, and Green-winged Teal. They've also seen a Mink, tree frog species, and lots of Coyotes. Who would like to adopt this area?

Twin Sisters Elk Drainage. Anyll Markevich adopted this area last year, and he's already documented territorial Great Horned Owls and Red-naped Sapsuckers, nesting Williamson's Sapsuckers, Western and Mountain Bluebirds, Vesper Sparrows, and Lark Sparrows; along with dozens of elk.

Walden Ponds. Karen Axe recently took over this area and has done a thorough job documenting potential breeding birds both around the ponds and along Boulder Creek. 2019 nesting species included Wood Duck (fledged young), Blue-Winged Teal, Cinnamon Teal, Virginia Rail, Sora, Green Heron, Osprey, Swainson's Hawk, Lewis's Woodpecker, Eastern Phoebe, American Dipper (nest building), and Cedar Waxwing.

White-tailed Jackrabbit. Photo by Steve Jones.