An Investigation of Wild Ungulate Impacts on Landbirds and Their Upland Aspen and Willow Riparian Habitat in Jackson Hole, Wyoming

Authors(s): S. H. Anderson and E. M. Anderson

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Publication Date: 0000-00-00

Type: annual report

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Abstract: Objectives First Year Primary Research Objectives 1.1 Quantify avian habitat use at the microscale (immediate substrate), mesoscale (35m-radius plots and stands) and macroscale (clusters of stands) levels. 1.2 Determine whether bird communities and species respond at multiple spatial scales to browse intensity as defined by politically similar categories of stands (i.e. the location of stands with respect to existence of supplemental elk feeding in the same land base) and/or ecologically similar categories of stands (see below). 1.3 Compare distributions of avian nest predators (e.g. Corvidae spp.) and a parasite (brown-headed cowbird (Molothrus ater)) with patterns of politically and ecologically defined browse intensity. 1.4 Investigate the role of landscape-scale parameters (including elements of human disturbance) in structuring landbird communities. 1.5 Compare the role of aspen ecotones in structuring bird communities in sites subjected to varying browse intensities. 1.6 Investigate the relationship between distance to supplemental feeding sites and bird community patterns. 2.1 Investigate the relationship among habitat parameters and browse intensity as defined by politically similar categories of stands. 2.2 Quantify recent browse intensity for each stand by measuring primary, or proximate browse effects (pellet groups, recent bark scrapings, twig browse). 2.3 Use evaluation of recent browse intensity to establish categories of stands subjected to similar browse intensities (i.e. ecologically similar stands). 2.4 Investigate the relationship between browse effects and distance to stand edge. 2.5 Investigate the role of distance to supplemental feeding sites on browse effects to habitat parameters. Second Year Objectives and Methods Second year objectives are similar to those of the first year with the following primary additions. 1. Compare rates of aspen stand area decay among politically similar categories of stands. 2. Compare landbird sensitivities to aspen stand area decay. 3. Investigate the relationship of browse intensity and landbird parameters in willow riparian communities. Findings and Status Landbird Analyses. The absence of adequate spatial and temporal browse intensity controls yields difficulty in interpreting the present influence of protracted historical browse regimes on habitat and associated bird community parameters. An initial approach to this problem includes classifying stands according to whether supplemental elk feeding occurs within the same federal land base; first-year avian and habitat data was gathered from 12 and 22 aspen stands associated respectively with and without feeding stations. Preliminary analyses indicate that landbird communities within the NER and within close proximity to State of Wyoming feed sites (hereafter feed stands) did not differ in overall relative abundance (p=0.598) or species richness (p=0.823) from communities sampled in other parts of the Jackson Hole valley (hereafter non-feed stands). Community-wide measures, however, provide little insight into avian patterns and contributing processes. The guild of aspen-obligate, understory-nesting species had greater relative abundance (p=0.002) and species richness (p=0.024) in non-feed than in feed stands (as hypothesized). As a member of this guild, the MacGillivray?s warbler (Oporornis tolmiei) occurred in greater relative abundance on non-feed compared to feed stands (p less than 0.001). Alternatively, the guilds of aspen obligate and of all cavity-nesting species had greater relative abundances (p=0.002 and p=0.008) and species richness (p=0.007 and p=0.028) in feed than in non-feed stands. As members of both these guilds, mountain bluebirds (Sialia currucoides) and tree swallows (Tachycineta bicolor) were individually found in greater relative abundance on feed compared to non-feed stands (p=0.011 and p=0.004). For detections at the stand level, ruffed grouse (Bonasa umbellus) (also a member of the aspen-obligate, understory-nesting guild) occurred in greater relative abundance within non-feed than in feed stands (p=0.007). Habitat Analyses. Serviceberry (Amelanchier alnifolia) and chokecherry (Prunus virginiana), the dominant upland shrubs palatable to elk and moose, were found at higher densities in non-feed compared to feed stands (p=0.001 and p less than 0.001). Moreover, the mean height of palatable shrub species (serviceberry, chokecherry and willow spp.) was higher on non-feed compared to feed stands (p less than 0.001 for all species combined). Understory vegetation volume was greater on feed than on non-feed stands (p less than 0.001), while vertical and horizontal heterogeneity did not differ significantly among stands (p=0.806 and p=0.961). Aspen suckers (dead and alive) less than 1m in height occurred in greater densities within feed than within non-feed stands (p=0.015). However, the proportion of browsed aspen suckers less than 1m in height and the proportion of dead aspen suckers less than 0.5m in height were both greater within feed than within non-feed stands (p=0.018 and p=0.002). Mean aspen sucker height was also higher on non-feed than on feed sites (p less than 0.005). Importantly, the above analyses stand as an initial attempt to uncover patterns across the landscape; classification of stands into two categories according to land base affiliation may be a gross oversimplification. However, given the temporal and spatial constancy of elk supplemental feed sites, this classification may be the preferable means of gaining insight into longer term browse effects. Analyses indicate ungulate pellet group densities are not uniformly higher in feed compared to non-feed sites. Thus, additional analyses clearly must explore patterns of recent browse intensity (using metrics described previously), as well as influences on longer term browse intensity (such as, for example, the position of aspen stands in relation to seasonal elk migrations).

Keywords: animal, mammal, ungulate, moose, Alces alces, bird, ornithology, Aves, habitat, Jackson Hole, Teton County, human activity, forage, feeding, food, elk, Cervus elaphus, Cervidae, wapiti, winter food supplementation, management, National Elk Refuge, migration, nest, nesting, habitat, corvid, Corvidae spp, brown-headed cowbird, parasite, Molothrus ater, MacGillivray?s warbler , Oporornis tolmiei, mountain bluebird, Sialia currucoides, tree swallow, Tachycineta bicolor, ruffed grouse , grouse, Bonasa umbellus