City Creek Nature Notes – Salt Lake City

May 25, 2017

May 23rd

Continental Scale Bird Population Trends – Part II

3 p.m. Unwittingly, I disrupt the community of birds just north of Guardhouse Gate. It is another warm, clear day, and I plan to spend this afternoon’s run developing my novice song bid, soundscape skills (May 6th). Over the weekend, I have assembled recordings of about forty-five birds from the Cornell Laboratory observing lists (May 20th), and they have been transferred to my telephone. The songs are sorted in order of similarity. Thus, I hope to learn the songs by listening to them throughout my day and by replaying the recording to identify unseen birds from their sounds alone. But this is not an easy skill to acquire. Some birds caw, others have warbling songs, and still others have four or five beat calls. The variations are endless: some warbling songs end on a high note, others on a low, some are long, others are longer. Call-like songs begin on a low-note, followed by a three or six beat high tone; others begin on a high-note, followed by a five count low-note. Others have a rapid trill. Nor is there much organization by either genus of bird or its outward appearance. The Black-headed grosbeak has song similar to the smaller Song sparrow, but the Rufous-sided towhee, which looks very similar to Black-headed grosbeak, has a two-beat call followed by a rapid, machine gun trill. The Lazuli bunting, which has a seed-crushing mouth sounds like the grosbreak and towhee, has a song that is a deeper throated version of the smaller Warbling vireo which has a mouth shaped for catching insects. Conversely, similarity of form can imply similarity of call. Some of the most colorful songbirds in the canyon are insectivores. The Warbling vireo, the Yellow warbler, and the Virginia’s warbler are similar in form and have variations on the same song, like some avian version of humanity’s proto-Indo-European language, but they do not all share the same family in the binomial nomenclature system. The Song Sparrow and House Sparrow are similar in form and voice tone, but their songs are very dissimilar.

Song birds along the first mile can be roughly divided into four communities: there is cluster between the Gate and mile 0.1 and picnic site 1 along both sides of the stream. A second group collects around the bend above picnic site 3 on the east side of the stream. A third is in a hollow below picnic site 5 on the west side, and a fourth along the western oak-covered slope near mile 1.0. These cluster at every 0.2-0.3 miles are connected by loose strings of individual avians. To these four neighborhoods, a five lays to the west of and along the Pipeline trail where the Gambel oak forest gives way to open grass and brush lands. The predators – Peregrine falcons, Red-tailed hawks, Cooper’s hawks, and American kestrels (Falco sparverius) – form their own neighborhood hovering in the sky over the song birds.

I begin at the first group near mile 0.1, where yesterday there was a riot activity. Since today, it is later in the afternoon, things are more subdued, but I can still distinguish six or seven different, unseen bird voices. Initially, I struggle with making any identification, and I become absorbed in loudly replaying about ten songs that represent the voices at mile 0.1. I listen to one song, and then try playing the two or three best candidate recordings to select the best match. After five minutes, I look up, and three birds have come out of the nearby screen of green. A Lazuli bunting perches on the top branch of a thirty foot Box Elder tree. On a nearby Gambel’s oak, a female House finch perches and stares. Across the road in the Box Elder, there is a bright flash of red and yellow midway down the tree. It is a male Western tanager in full breeding plumage, and I start replay a recording of his species in order to keep his attention. For the two months of its breeding season, the head of the tanager turns a brilliant red, and this contrasts with its vivid yellow underplumage and black back. This male has caught the lengthening rays of afternoon sunlight that is softened by moisture in the air, and its red iridescent plumes blaze.

After working with the recordings for one-half hour, I am able to make rudimentary identifications by sound alone of the the Western tanager, a Lazuli bunting, a Warbling vireo, a Song sparrow, and American robin. What strikes me about this lower community is its heterogeneity. There are perhaps seven species all sharing the same one-quarter square mile. They cooperate in sharing the space. Birds are known to share the same forest space by specializing in different food niches, it is early in season and food may be plentiful, and territorial nest building may not have been completed.

Traveling up canyon, the bird community in the hollow near picnic site 5 is populated by only Warbling vireos. Further up canyon, a lone Spotted towhee caws and trills. American robins are dispersed along the first mile road.

Spring Azure butterflies have had a mini-R reproductive explosion. Usually there are three or four larger adults along the first mile road. Today, I count 20 smaller streaked blue versions only three-quarters of an inch in size. The next generation has hatched, and they play among newly cut grass. The City has come through the canyon, and as a fire prevention measure, it has mowed down the two and three foot grass around each picnic area. The air is sweet with cut-grass smell, and further back from the sickle’s cut, the green grass is interrupted by the first loud yellow of newly opened Toad flax (Linaria vulgaris), also called Butter and Eggs plant. This common roadside noxious weed has a beautiful, intensely yellow and orange, orchard like bloom.

Coming back down canyon close to six in the evening, these bird communities are silent, and only the evening town criers of the canyon, the House finches, repeat their their one-high, two low, call of three notes. Near mile 0.5, an immature Terrestrial gartersnake (Thamnophis elegans) crawls across the road. The garter eats insects, e.g. – the Stink bugs that rest along the roadside and snails (May 16th).

Incongruous to this serenity, a group of ten people walk up the road, and two have small caliber handguns strapped to their sides. These “open carry” gun rights advocates, whose right to openly carry guns is sanctioned by the state legislature, have no need for these weapons. Discharging them in the canyon below mile 0.4 violates city and county ordinances, and regardless of the legality, their attempt to drag society back into uncivility and barbarism of some imagined historical western landscape is uniformly disapproved of by the majority of members of the surrounding neighborhoods. Regularly, such displays or the discharge of firearms results in canyon walkers making worried telephone calls to the police, and the police do respond to hand out tickets. While I have some appreciation of how individualism and capitalism can drive people into a mindset that perpetually fears others, this group is not in any danger in the canyon this evening. No one is hiding in the bushes ready to rob them, and their flashy presence in the canyon is an unwelcome intrusion. Like the songbirds around them and the red blaze of the tanager, their weapons are an overstated claim for social attention and of personal territory.

* * * *

The National Audubon Society recently has become a leader in continental scale studies of populations and of future threat forecasting. In 2013, the National Audubon Society released their report titled “Developing a Management Model of the Effects of Future Climate Change on Species: A Tool for the Landscape Conservation Cooperatives” based on its Christmas Bird Count (discussed below) and BBS data (National Audubon Society, Schuetz, Distler, Langham, 2013). Coupled with global climate models, the Audubon’s Christmas Bird Count data allowed the Society to model changes in bird summer and winter ranges, summarized in national maps, based on varying degrees of global warming. In the Great Basin (and in the canyon), their model predicted increases in bird species richness during the winter season and declines in bird species richness during the summer season (id, 27-29, Figs. 2.8-2.9). In an updated study, Langham and colleagues from the Society used further advanced modelling techniques with respect to 588 North American continental birds, and they forecasted that by 2080 under a high-emissions high-warming scenario, about 53 percent of the 588 species would find that 50 percent of their current range, particularly for summer breeding, would become unsuitable (Langham et al. 2016).

With respect to continental-scale population trend studies, the Audubon Society’s annual Christmas Bird Count has collected bird counts since 1901. Unlike professional studies, the Christmas Bird Count (CBC) suffers from a number of inherent design controls. CBC bird identifications are made by error prone amateurs at differing locations and differing types of locations, e.g. – in the field or at feeders, between each annual sampling. Fluctations in the number of observers between years can introduce observation bias. Those characteristics limit the ability to use CBC data to predict trends in bird populations using traditional statistical techniques. Conversely, the CBC has been the collecting massive amounts of data from numerous amateurs around the country for more than a century. For example, in the 2016 count, over 56 million birds were manually counted. Increases in inexpensive computing power and application of advanced statistical techniques eventually allowed for the use of this citizen science data to make reasonably statistically confident statements of about trends in bird populations sampled from a wide variety of habitats. In particular, the mathematical techniques of multi-level regression, also called hierarchical modelling, allows for the extraction of bird density trends over time from the massive, but uncontrolled, data sources collected by the Audubon Society. Since 1990, habitat change from climate warming has become an important issue. Application of these analytic improvements also allow trends to be examined in the context of varying habitats, and thus, making the CBC data useful for exploring trends in habitat change from development and climate warming affects bird populations.

Soykan and colleagues with the National Audubon Society estimated North American continental populations of 551 North American bird species and for a subset of 228 species that do not frequent bird feeders using the Society’s annual Christmas Bird Count data (Soykan et al. 2016). They found that for all 551 species, 68 percent had increasing density trends from 1966 through 2013. Thus, 32 percent have a declining trend, a fact exploited in NACBI glosssy annual “State of Birds” reports. For the subset of 228 species, Soykan et al found an 0.9 percent growth trend across 1966 to 2013. They noted the geographically, declining species were concentrated at lower latitudes and increasing species were located at higher latitudes (id), and this suggests that generally, bird populations are shifting their ranges northward. For the future canyon, this is consistent with Schuetz, Distler and Langham’s 2013 modelling suggesting that warmer climates would increase winter species diversity in the Great Basin as birds move their ranges north (above).

Soykan et al’s supplemental data provides further insight into Utah trends (Soykan et al. 2016), but it also underscores the problems and differences of professional verses amateur data collection. Conflicting with the Parrish, Norvell and Howe declining Utah trends for 1992 to 2005, Sokyan and colleagues found from CBC counts for 1966 to 2013, an increasing bird population trend of 2.7 percent for Utah (Table S.4) and 2.8 percent for the Great Basin region (Table S6). Students of introductory statistics will recall the Rule of 70: the doubling time or halving time of a population can be estimated by dividing 70 by the annual rate. Thus, the CBC trend suggests that Utah bird populations will double in 25 years, while the Parrish, Norvell and Howe rate suggests populations would halve in 70 years.

Although overall, Soykan et al’s continental population trends derived from CBC counts were statistically similar to 228 professional BBS specie trends, for a small subset of 33 species, CBC and BBS trends significantly differed (Table S.9). Some of the differences involve species frequently seen in the spring canyon. For two species, Swainson’s Hawk and the Black-headed Grosbeak, the CBC found continental declines around 3 percent per year, while the BBS surveys found increases of less than 1 percent per year. A three percent decline suggests populations will halve in about 25 years. For eight other species found in the canyon, the CBC found a slight increasing population trend, while BBS found populations declining at more than 1 percent per year: Song Sparrow, American Kestrel, Belted Kingfisher, Mourning Dove, Orange-crowned Warbler, Yellow Warbler, Chipping Sparrow, and the Broad-tailed Hummingbird.

Again, overall bird population studies continue to indicate that currently and for the near future, bird specie diversity and bird populations should remain stable or have a slight decline, as indicated by the Parrish, Norvell and Howe studies (Parrish et al. 2007). Soykan et al and Langham et al conclude overall birds are moving their summer ranges northward and they are decreasing the area of the summer and winter ranges around the best habitats in response to a warming climate, and under that scenario, Utah bird populations would increase as birds move further north. But whether population trends will decline in a severe global warming occurs scenario, whether they will increase as more birds move their ranges north in response to southern latitude warming, or whether Utah bird populations will increase after the reversal of the current Intermountain drought phase of the Pacific Quasi-Decadal Oscillation (February 7th) remains to be seen. Continued monitoring, such as that occurring through professional and citizen science surveys, is the only means to have a definitive early warning of any dramatic change, for better or worse. Other unanticipated changes, both good and bad, may also occur.

These mathematical models of bird populations, as with proof of biophilia studies, provide only the most general of signs and no clear answers. Proof to a reasonable degree of scientific certainty cannot be found in the statistics of bird populations, and thus, we are forced to fall back on human values and human judgment in deciding what to and how to protect nature. But as with local weather and the Pacific Quasi-Decadal Oscillation, it is only by looking on a continental scale that over-arching patterns in nature can be seen. A local-only perspective, like Plato’s prisoners in his allegorical cave, can give us a limited, uninformed, and wrong view of the world.

There is a further brilliance to the CBC data and Schuetz, Distler and Langham’s 2013 study. They provide detailed ranged summer and winter maps for 36 bird species of concern (id, 114-181) on a continental scale and with previously unseen fidelity (Schuetz, Distler and Langham’s 2013). Presumably, such maps can be generated for all birds in the CBC study. Previously, bird summer and winter range maps were rendered with broad colored areas across a U.S. map with northern and summer range lines, e.g. – those seen in my old 1990 Peterson’s Western Birds guide or my favored, dog-earred 1966 Guide to Field Identification of North American Birds, illustrated by Arthur Singer. The ranges of migration were indicated by broad directional lines. By combining CBC bird observations with satellite habitat data, Schuetz et al render detailed core range maps.

* * * *

On May 23rd, 2012, Lowell Bodily, Salt Lake Valley Health Department, again reported on homeless tent camps in the valley, and he notes that some homeless camp along the Bonneville Shoreline Trail in and near City Creek Canyon (Salt Lake Tribune). On May 23rd, 2006, the Lion House reports that it hosts about 82,000 visitors per year (Salt Lake Tribune). (In the 1850s, the Lion House sat next to the tollgate that controlled access to City Creek Can yon.) On May 23rd, 2002, in a letter to editors of the Salt Lake Tribune, a Sandy resident decries how a new luxury home has defaced the beauty of Ensign Peak and City Creek Canyon (Salt Lake Tribune). On May 23rd, 1996, Anschutz Ranch East Pipeline Inc. proposes to build a crude oil pipeline from Park City that would cross through City Creek near the water treatment plant (Salt Lake Tribune, June, 24, 1996). On May 23rd, 1914, the Salt Lake Telegram published a photograph layout and description of driving the new scenic boulevard up City Creek, along 11th Avenue and down 1300 East (Salt Lake Telegram). On May 23rd, 1905, Land and Water Commission Ben D. Luce requested that the City council to ban automobiles from driving up City Creek Canyon due to the possibility that they will cause accidents by frightening horses (Salt Lake Herald).

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