City Creek Nature Notes – Salt Lake City

May 22, 2017

May 21st

Filed under: Birds, Leopard slug, Light, Sounds, Weather — canopus56 @ 4:40 am

Utah Bird Population Trends

8:30 p.m. I am on a short, quick jog near twilight, and towering broken clouds float from the west to east over the lower canyon. As the sun nearly sets, dimmed green and brown ridgeline contrasts with slate gray cloud bottoms below the descending sunset line, but the cloud tops are enveloped in a bright pink and white hues against the deepening blue sky. Two Leopard slugs take advantage of the cool evening to cross the road. Twilight turns to night. Unlike my snowbound fall night run (December 12th) which focused on the sound of silence, tonight the crashing white noise of the stream drowns out any thoughts as I return to the gate through the darkness.

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Bird populations are almost impossible to estimate with any accuracy. The best that can usually be done is to measure changes in the density of birds and from those changes a change in the overall population level can be inferred. Numerical population estimates exist for Utah game waterfowl birds and endangered species that travel along the eastern branch of the Pacific Flyway that passes through the Great Salt Lake. The Pacific Flyway is one of the three great North American migratory bird flyways that stretch from Canada to central Mexico. Thus, the populations of many birds see in the canyon that winter to the south is dependent on the availability of habitat two thousand miles to the south. Similarly, bird populations seen to the north and south of Utah are dependent on the marshes of the Great Salt Lake. There is no alternative route for birds to cross Utah and Nevada’s arid lands.

Olson of the U.S. Fish and Wildlife Service reports a 13 percent increase in waterfowl birds between 2009 and 2016 (55,868 divided by 49,464 birds) (Olsen 2017). (The Utah study methodology changed in 2009 and this prevents examining longer term trends back to 1992). With respect to non-game birds such as those smaller song birds in the canyon, Parrish, Norvell and Howe with the Utah Division of Natural Resources 1992 to 2005 study of 37 Utah bird sites found that (Parrish et al. 2007; Novell, Howe and Parrish 2005). Their study created the longest running dataset of high quality bird density estimates for the western United States (Parrish et al. 2007, 77). About half of Utah’s 440 bird species are residents; they other half are annual neotropical migrants; and, more than 70 percent of those birds use riparian habitats, like the Jordan River, as habitat during part of their life cycle (Parrish et al. 2007, 12). Based on estimated the density of 202 species of Utah birds from 1996 to 2005 from observations and recaptures, Parrish and his colleagues found that overall Utah bird populations have declined 5 percent over the thirteen years from 1992 to 2005 (id, 4, 67, Fig. 8). The Utah bird decline should be viewed within the context of the fifteen year drought cycle. The Great Salt Lake water level has been declining, its marshes have less water, and other bird refuges are drier. Population declines would be expected from such changes in habitat. Parrish, Norvell and Howe did not have a study site in City Creek Canyon.

The decline in Utah neotropical migratory birds is not uniform for birds found in City Creek Canyon. Between 1995 and 2001, the density of American Goldfinches, American Robins, Black-headed Grosbeaks, Broad-tailed hummingbirds declined, but the density of Yellow Warbler’s increased (Novell, Howe and Parrish 2005, 561-562, Figs. 2-3). Gross waterfowl populations along the Great Salt Lake are increasing, despite the drought. Available copies of their 2007 report do not provide density information disaggregated by individual species. In summary, Utah state neotropical bird studies indicate that the population of birds in the canyon relatively stable, but populations may decline further based on changes in local climate.

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Given that a high proportion of Utah birds that use riparian habitats, Parrish, Norvell and Howe recommended adoption of various management activities to improve habitat along Utah’s waterways without necessarily waiting for further study demonstrating the efficiency of remediation efforts in improving bird populations (Parrish et al. 2007, 76-77). Cause and effect are well known and obvious in these circumstances. In 2011, the Utah State Legislature authorized the expenditure of 37 million USD to support the Utah Watershed Restoration Initiative for joint private-public riparian rehabilitation ventures (Clark, A., and Utah Department of Natural Resources, 2013; (Utah Department of Natural Resources, 2017b). Through 2016, the Utah Division of Wild Resources reports that it has completed 1,607 projects covering 1.3 million acres of Utah Wetlands.

The Utah Watershed Restoration Initiative has funded Yellow starthistle abatement in City Creek Canyon during 2010 through the present (Utah Department of Natural Resources, 2010, 2016, 2017a, 2017b). Those projects included chemical spraying of 8 acres in Pleasant Valley to control the weed in 2017 (Project Id. 3693), 2016 (Project Id. 3404), 2013 (Project Id. 221), spraying 70 acres in 2011 in Pleasant Valley (Project Id. 1642), and spraying 150 acres five miles up the canyon in 2010 (Project Id. 1464). Another spraying in the canyon is proposed in 2018 (Project Id. 4040). The Initiative funds the Utah Conservation Corps currently working in City Creek (May 17th, October 16th) (Utah Department of Natural Resources, 2017a).

On May 21st, 2003, in a letter to the editors of the Salt Lake Tribune, Richard Pieros observes how new FAA landing flight paths for the Salt Lake International Airport over Emigration Canyon, City Creek Canyon and the Avenues has resulted in loss of solitude. (Later, the FAA revised the flight paths and airliners no longer take off or landing over City Creek Canyon or the Avenues, except in rare unusual instances. This transfers the airport noise burden to West Valley City residents and to wildlife along the shores of the Great Salt Lake.) In May 20th, 1994, Bryant Elementary School Children participated in a neighborhood cleanup of Memory Grove and City Creek Canyon (Salt Lake Tribune). On May 21st, 1916, City Engineer Sylvester Q. Cannon planned to measure the volume of lakes in City Creek Canyon in order to see if they were suitable to act as reservoirs (Salt Lake Tribune).

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