City Creek Nature Notes – Salt Lake City

December 8, 2016

December 9th

Counting Nests

8:00 a.m. On December 8th, I completed an inventory of nests in the first two miles of the canyon done on December 1st through the 7th, and the results are not what I expected. I had thought that small birds would prefer to nest away from the road and expected to find more nests along the trails, but they predominantly nest close to the road and stream. I count thirty-nine nests in the first two miles. For insect nests, two are Paper wasp nests and six are Bald-faced Hornet nests. The remaining thirty-one are birds’ nests. Of the thirty-one bird nests: nine are delicately woven bag nests for small birds such as hummingbirds; four are hanging and finely woven grass nests suitable for small and medium sized birds; one is a cliff stick nest of the falcon pair; five are snag nests in drilled into hollow cavities of snag or dead tree trunks; and the remainder are circular or platform twig nests.

All but one falcon nest is along or adjacent to the paved road. Initially, I thought that there would be many small bird nests along the Pipeline trail in the scrub oaks, but there are none. Checking the trail a second time, I realize that the Gambel’s oaks on this west side of the canyon would be too hot in late May and early June for fledglings. Birds are nesting in the coolest part of the canyon, next to water. Mountain chickadees and Black-hooded chickadees both use snags for nesting and do not build twig nests (Hutto, p. 34-35).

There are many snags, i.e. – dead trees, in the first two miles of the canyon. In addition to the chickadees, the Hairy woodpecker (Picoides villosus) and the Northern flicker rely on snags for shelter and nesting (Hutto 34-35, Werstack, 49-50). At picnic site 7, a good example is in a 40 feet vertical snag on the other side of the creek. At its top is a tear shaped excavation that indicates there is a nest in the hollowed out tree. It is possibly the primary or secondary nest of the Northern flicker seen in this area. A second snag at the up canyon end of picnic site 9 has many smaller holes drilled in it, and these may be suitable for chickadee nesting. Birds prefer snag trunks between 10 inches to 14 inches for making a hollowed-out tree nest. In 2016, Werstack et al estimated that there are 149 million snags in Utah suitable for bird nesting, but I estimate that there are probably about 20 to 30 suitable snags in the first two miles of the canyon.

Where the Pipeline Trail skirts the based of cliffs on north side of the road near mile 1.0, a Peregrine falcon pair has a large stick nest. The nest is perched on a rock ledge about 300 feet from the trial. It cannot be accessed either from above or below by predators, and it is only faintly visible with the naked-eye. Binocular or a monocular magnification is needed to see any detail. Although the nest is currently empty, from April to June, I watched the pair and fledglings almost every day. Not in this survey, but seen last year, is a large circular stick nest in the top of an eighty foot fir tree near mile 2.4. That nest was occupied by a breeding pair of Cooper’s Hawks.

Goodfellow and Hansell describe the architectural skill that birds use to construct the many woven grass and smaller twig nests. When making hanging-basket grass or circular twig nests, some birds will use a hook technique similar to Velcro. As noted on September 5th, the design of Velcro was inspired by the burrs of the burdock plant. Birds also mimic the burdock burr. They choose twigs with small hooks near the ends or twist grasses to make hooks and as they weave a twig into the nest, they secure the twig by hooking the end around an earlier placed twig.

My instinct is that there are too few nests for the volume of birds seen during the March to May nesting season, but my bird count data suggests the number is about right. My birding log between March 2015 and May 2015 of last year (Fisher 2015) shows 166 bird sightings. Given that these involve resighting the same birds multiple times, 39 nests is reasonable. During the winter and spring, small Black-hooded chickadees, Mountain chickadees and Stellar Jays are the most prevalent bird in the canyon. Other birding logs made by Tracey Aviary professionals are stored at the Cornell University’s Ornithology Laboratory’s eBird database for the “Bonneville/City Creek” observing area (Cornell 2016). Are there and where are any missing birds’ nests?

Hornets were far more common than I had previously thought. A nest down canyon of picnic site 6 is notable. The late afternoon Sun makes it glow. It is twice the size of a basketball, and it precariously sits intertwined with the smallest upper branches at the top of a 100 foot tall Rocky Mountain cottonwood. The nest sways back and forth in the wind, but it is the most secure of the five hornet nests in the lower canyon. Although I see and photograph this nest

These hornet nests provide another link in the food chain. The hornets drink nectar and eat other smaller insects. In turn, hornets are the another food source for the many small birds seen in the spring in the first canyon mile.

In Thoreau’s “Journal” on December 9th, 1855, he visually observes his first owl in ten years, having only their heard their calls during that period.

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