Boulder Audubon's Nest Box Monitoring Program

• Introduction
• The Bluebird Nesting and Monitoring Season
• Flowers at Walker Ranch
• Other Animals at Walker Ranch

Boulder County Audubon Society volunteers have completed another successful season of monitoring nest boxes for bluebirds and other species. For 2007, the collaboration with Boulder County Parks and Open Space was expanded to include boxes at Betasso Open Space, in addition to Walker Ranch/Meyers Gulch. We have also begun a collaboration with City of Boulder Open Space and Mountain Parks with the installation of boxes on Shanahan Ridge. There is discussion of adding additional nest box trails for the 2008 season. The added trails will require more volunteers. Monitoring the nests is enjoyable and rewarding; click here for a description of what is involved.

In the 1980s, the Western Bluebird was considered "rare and declining" in Boulder County, meaning that there were fewer than 3 known nesting pairs. That is no longer the case, perhaps partly because of nest boxes at Walker Ranch and elsewhere in the county. (Current rare and declining list)

The table below summarizes bluebird fledging at Walker Ranch for 2005 through 2007. Not only are Western Bluebirds no longer rare, it appears they may become the majority bluebird species in the park. A possible reason for the changing species ratio is the mix of nest sites at Walker Ranch. Western Bluebirds seem to prefer boxes in areas with large trees, while Mountain Bluebirds are more common in boxes on fence posts in open fields.

The Walker Ranch nests are at an elevation of about 7300 feet, so nesting is a bit later than in many parts of the country. The birds start building nests around the first of May and lay their first eggs in mid-to-late May. Once the first egg is laid, another is added each day, typically for three to five more days. Brooding starts when all the eggs have been laid, so that all will hatch on the same day, 12-14 days later. The chicks fledge 18 to 21 days after hatching.

While the focus of the program is bluebirds, other cavity nesters also benefit. At Walker Ranch in 2006-07, these included Tree Swallows, Violet-green Swallows, Mountain Chickadees, White-breasted Nuthatches, and House Wrens. The swallows nest later than the bluebirds. One pair, in 2006, added feathers to and used a bluebird nest after those chicks fledged.

An experimental nest box trail was installed at the Betasso Open Space in 2006 and expanded to nine boxes for the 2007 season. The boxes proved very popular with the birds, as four were used first by bluebirds, then subsequently by swallows. Betasso is at lower elevation than Walker Ranch, about 6500 feet, which may influence the ratio of Western to Mountain Bluebirds.

Five boxes were installed late in the season near the Shanahan Ridge Trail, on City of Boulder Open Space. We knew at the time that we were probably too late for bluebirds to use the boxes. However, one box was used successfully by Violet-green Swallows, and we located a Western Bluebird nest in a snag near one of the boxes.

Some of the Audubon Society volunteers joined Denny Morris, of Boulder County Parks and Open Space, in April to visit box locations changed since the 2005 season.)	Male Mountain Bluebird perched on fence near box.	Female Mountain Bluebird. Nice pose near a box with chicks. (6/8/07)	Violet-green Swallow at Shanahan Ridge, (7/9/07)	Tree Swallows also use the boxes. They nest later than the bluebirds. In several cases this year, a pair moved into a bluebird nest after those chicks fledged.
Chicks at 2 or 3 days of age. (6/14)	Female Mountain Bluebird with food. (6/14)	Male Western Bluebird with food for nestlings. (7/10/07)	Western Bluebird nestling nearly ready to fledge from natural cavity at Shanahan Ridge. (7/9/07)	Mountain Bluebird 3 to 4 weeks after fledging. (7/18/07)
Western Bluebirds checking a box inside and out before starting a nest. (4/21)	Female Mountain Bluebird checking on the box. After the box has been opened for monitoring, they often perch briefly to check before re-entering the box. (5/26)	Female Mountain Bluebird with nesting material. (4/23)	Checking a box. Some of the boxes open at the front; this one opens at one side. (5/26)	Nest with 6 Mountain Bluebird eggs. (5/26)

Ball cactus close up. (4/23)	Sand Lily (or Star Lily). (5/2)	Wild Geranium. (5/26)	Gaillardia (Blanketflower) with 2 firemoths. The moths are Gaillardia specialists. Their coloration provides excellent camouflage, especially when they are carefully aligned with the flower's colors. (6/14/06) Only a single firemoth was spotted in the 2007 season.
Gaillardia with butterfly, probably a checkerspot. (6/29)	A small wild rose. (6/21)	Mariposa Lily. (6/29)	Narrow-leaved Penstemon. (6/21)
Irises. (5/26)	Early Larkspur. (5/17)	Pasque flowers are among the earliest to bloom. (4/23)	Ball cactus near one of the nest boxes. (4/23)

There was a coyote den under one of the buildings. We didn't see the pups, but we did get a nice look at this coyote passing by.	White-tailed Deer are fairly common, although not usually this close by.	Other birds also nest at Walker Ranch without occupying our nest boxes. Here a mother Northern Flicker feeds her chicks. (6/14)	The Dark-eyed (Grey-headed) Junco probably nested at higher altitude.	There was a male Broad-tailed Hummingbird on this twig every time we passed by from May 17 to July 6. The males don't help raise the brood. The perch was consistently used in the '07 season as well, perhaps by the same bird.	This Lark Sparrow probably was a transient visitor, nesting elsewhere.
Meadowlark with food for chicks in an unknown nest location. Meadowlarks nest on the ground, and don't use the nest boxes. (6/29/07)	Violet-green Swallow chicks waiting for food. The parent feeds without landing. These chicks should fledge within a day or two of this picture. (7/28)	Tree Swallow hatchlings, just a few days old. They have only the beginning stubs of feathers. (7/28)	Male Red-winged Crossbill. Crossbills were spotted a number of times during the season. They aren't cavity nesters; none of the volunteers spotted nests or adults feeding young. (4/22)	Although it's conceivable that the Killdeer might nest at Walker Ranch, its nest more likely would be nearer a body of water. There are lakes within a few miles.	Vesper Sparrows were very common throughout the season. This one is waiting to take food to a chick. We didn't locate the nest. (6/20/07)