Statwide Population Monitoring, Riparian Birds in Utah

Background/Question/Methods Approximately 75% of Utah's avian species use riparian habitats at some time during their life cycles and at least 80% of this habitat in Utah has been lost or altered since settlement. Riparian areas now comprise less than 1% of land cover in Utah. In 1992, the Utah Division of Wildlife Resources began a statewide neotropical migratory bird (NTMB) monitoring program in this critical habitat. Unlimited distance sampling methods have been implemented at over 50 riparian survey sites statewide. Products include monitoring bird species density trends and community composition in riparian habitats throughout the state. Many projects goals directly address focal species identified as Utah Partners in Flight priority species in the Utah Avian Conservation Strategy plan as well as priority habitat and avian species listed in the Utah Comprehensive Wildlife Conservation Strategy. Our primary study goals are 1) to assess population trends for focal avian species, 2) describe changes in vegetation over time, and 3) investigate how these two processes are related by creating bird-habitat association models. Results/Conclusions Recent results from population trend analyses suggest that the patterns of annual variation and regional synchrony seen in riparian-dependent species groupings, density, and other parameters may be driven by landscape-scale effects on habitat. To better understand these large scale effects, riparian-bird habitat association models are being developed using 17 years of statewide bird and vegetation data. Our model results will form the basis for the development of management guidelines that will inform riparian restoration and conservation in Utah, both at the species level (i.e. threatened and endangered species) and the community level to maximize species richness and diversity. Riparian bird-habitat models results will be presented and the framework for riparian management guidelines will be discussed.

Utah Partners in Flight (UPIF), a cooperative organization of state, federal, private, and non-governmental organizations dedicated to conserve Utah’s landbirds, established this study in 1992 to document bird population trends in Utah’s riparian areas. The work was initially designed to compliment existing efforts, to respond to rising regional concerns, and to provide land managers and the public with relevant local information. Specifically, we designed the study to detect a 50% linear decline in abundance over 10 years with 80% power at an alpha level of 0.10. This report summarizes the first 14 years of this on-going effort, and concludes that riparian bird populations have undergone statewide declines of approximately 5% per year during the 1992-2005 period. Linear trends in the two most sensitive metrics used in the study, abundance and annual survival, agree in the direction and magnitude of these declines. Declines observed in abundance are considered statistically significant. There was no significant linear trend in overall species richness. This first analysis is intentionally large-scale and taxonomically inclusive, capturing statewide patterns in broad strokes. On-going and planned analyses will work to detail the site, species, ecoregion, and agency-specific trends. These results do not implicate specific causes or mechanisms, but on-going management activities, concurrent regional drought, and regional anthropogenic impacts are briefly discussed. This work represents the longest continuous study of this extent western North America. Thirty-one riparian sites were initially chosen for monitoring using point transect (detectabilitycorrected abundance estimation) beginning in 1992. Additional sites were added in later years; 37 sites with consistent data representing statewide patterns were chosen for this monitoring analysis: 15 sites total on Bureau of Land Management (BLM) managed lands, 13 on United (5) State Forest Service (USFS) managed lands, 2 sites on National Park Service (NPS) managed lands, 2 sites on United States Fish and Wildlife Service (USFWS) managed lands, and 5 on either Utah Division of Wildlife Resources (UDWR), Bureau of Reclamation (BOR), or privately managed lands. Four of these sites were selected for continuous effort mist net sampling (survivorship estimation via mark-recapture banding) beginning in 1994, with four more sites subsequently added. These 37 sites are most representative of low and mid-elevation riparian areas on publically managed lands. Data from the study has established bench-marks for riparian habitats in Utah and the region. As such it represents a great success in UPIF’s cooperative, diversified, funding model for long-term and large-scale applied ecological research. Current and future uses of these data include: 1) providing managers with the region- and habitat-specific set of references, with important estimates of natural variation, needed for assessments of habitat quality, managementaction impacts, and restoration success; 2) providing managers and researchers with the first baseline abundances and survival estimates for many of Utah’s riparian species; 3) estimating trends in population and survivorship for individual species of management concern; 4) correlational analyses designed to formulate testable hypotheses about the causes and scales of population change, and 5) compilation into bird species- and community-habitat associations designed to help guide conservation and restoration activities.