Geology topics

Scott L. Durst

Publications and source records attributed to Scott L. Durst.

6 recordsLinked to original sources

USGS2018

Extreme drought alters frequency and reproductive success of floaters in Willow Flycatchers

Changes in habitat quality, including those caused by extreme events like droughts and floods, could alter costs and benefits of territoriality and thereby the prevalence and reproductive consequences for individuals capable of breeding that do not do so (floaters). We studied floating behavior in a population of Southwestern Willow Flycatchers ( Empidonax traillii extimus ) in central Arizona during one year of extreme drought, one year of lake inundation, and three years of near average precipitation. In all years, most floaters were second year (SY) males, and most subsequently settled outside of the patch where they were detected in the floating year, suggesting that floaters did not “queue” at high-quality territories in order to achieve higher reproductive success in subsequent years. Instead, cohorts that floated in non-drought years had lower apparent survival and lower reproductive success compared to territorial birds. In the extreme drought year, however, the number of floaters was 1.5 times greater than in all other years combined, more females floated, and apparent survival and mean annual productivity in subsequent years was higher for males that floated in that year than for those that were territorial. Inundation of habitat due to rising reservoir levels did not result in an increase in floaters because many birds nested in inundated areas where trees projected above the water so that the relative amount of available habitat was not reduced to the extent habitat models predicted. Overall, our results indicate that the prevalence and reproductive and demographic consequences of floating can change under extreme climatic events like severe drought.

The Auk↗

USGS2017

Survivorship across the annual cycle of a migratory passerine, the willow flycatcher

Annual survivorship in migratory birds is a product of survival across the different periods of the annual cycle (i.e. breeding, wintering, and migration), and may vary substantially among these periods. Determining which periods have the highest mortality, and thus are potentially limiting a population, is important especially for species of conservation concern. To estimate survival probabilities of the willow flycatcher Empidonax traillii in each of the different periods, we combined demographic data from a 10-year breeding season study with that from a 5-year wintering grounds study. Estimates of annual apparent survival for breeding and wintering periods were nearly identical (65–66%), as were estimates of monthly apparent survival for both breeding and wintering stationary periods (98–99%). Because flycatchers spend at least half the year on the wintering grounds, overall apparent survivorship was lower (88%) on the wintering grounds than on the breeding grounds (97%). The migratory period had the highest mortality rate, accounting for 62% of the estimated annual mortality even though it comprises only one quarter or less of the annual cycle. The migratory period in the willow flycatcher and many other neotropical migrants is poorly understood, and further research is needed to identify sources of mortality during this crucial period.

Journal of Avian Biology↗

USGS2008

Yellow-billed Cuckoo Distribution, Abundance, and Habitat Use Along the Lower Colorado River and Its Tributaries, 2007 Annual Report

This 2007 annual report details the second season of a 2-year study documenting western yellow-billed cuckoo (Coccyzus americanus occidentalis) distribution, abundance, and habitat use throughout the Lower Colorado River Multi-Species Conservation Program boundary area. We conducted cuckoo surveys at 40 sites within 14 areas, between 11 June and 9 September 2007. The 169 surveys across all sites yielded 163 yellow-billed cuckoo detections. Cuckoos were detected at 25 of the 40 sites, primarily at the Bill Williams River National Wildlife Refuge (NWR) study area (n = 139 detections; 85 percent of all detections). Detections declined slightly through the cuckoo breeding season, with most detections occurring in the first and second survey periods (n = 92; 54 percent). We detected breeding activity only at the Bill Williams River NWR, where we confirmed 27 breeding events, including two nesting observations. However, the breeding status of most detected birds was unknown. We used playback broadcast recordings to survey for yellow-billed cuckoos. Compared to simple point counts or surveys, this method increases the number of detections of this secretive, elusive species. It has long been suspected that cuckoos have a fairly low response rate, and that the standard survey method of using broadcast recordings might fail to detect all birds present in an area. In 2007, we found that the majority (84 percent) of cuckoo detections were solicited through broadcast at all study sites. The number of solicited detections was highest during the first survey period and declined as the breeding season progressed, while the number of unsolicited detections (cuckoos heard calling before broadcast was initiated) remained fairly constant through the first, second, and third survey periods. The majority (66 percent) of cuckoo detections, solicited or unsolicited, were aural, 23 percent were both heard and seen, and 11 percent were visual detections only. We also found that 50 percent of all responses by cuckoos were evenly split between the first and second broadcasts at sites with >10 detections, while 45 percent of responses occurred after a single broadcast at the sites with <10 detections. We refined our collection of vegetation data in 2007 and found that across the entire study area the dominant tree species were tamarisk (Tamarix spp.), willow (Salix spp.), and cottonwood (Populus spp.). The smallest size class (<8 cm diameter at breast height) trees were the most common and were dominated by tamarisk, but cottonwood and willows were well represented in the larger size classes. Sites that were occupied by yellow-billed cuckoos generally had higher canopies, denser cover in the upper layers of the canopy, and sparse shrub layers compared to unoccupied sites that consistently had higher densities of woody species. As most occupied sites were within the Bill Williams River NWR and most unoccupied sites were at Grand Canyon National Park/Lake Mead National Recreation Area, vegetation characteristics at these study areas drove the cuckoo distribution patterns we observed in 2007. However, there was a range of habitat conditions in locations that were used by yellow-billed cuckoos across the entire lower Colorado River Multi-Species Conservation Program study area. We measured microclimate variables (temperature, relative humidity, soil moisture) at occupied and unoccupied sites, and found that, across the entire study area, occupied sites were consistently cooler during the day and more humid during the day and night compared to unoccupied sites, but that soil moisture did not differ between occupied and unoccupied sites. While most cuckoo detections occurred at Bill Williams River NWR, with generally cooler and more humid conditions, cuckoos were also detected at study areas that had hotter and dryer microclimate conditions. We did not find any relationship of canopy cover characteristics to temperature or soil moisture, suggesting

Open-File Report↗

USGS2008

Southwestern Willow Flycatcher Breeding Site and Territory Summary - 2007

The Southwestern willow flycatcher (Empidonax traillii extimus; hereafter references to willow flycatcher and flycatcher refer to E.t. extimus, except where specifically noted) is an endangered bird that breeds only in dense riparian habitats in parts of six Southwestern states (Arizona, New Mexico, southern California, extreme southern Nevada, southern Utah, and southwestern Colorado). Since 1993, hundreds of Southwestern willow flycatcher surveys have been conducted each year, and many new flycatcher breeding sites located. This document synthesizes the most current information available on all known Southwestern willow flycatcher breeding sites. This rangewide data synthesis was designed to meet two objectives: (1) identify all known Southwestern willow flycatcher breeding sites and (2) assemble data to estimate population size, location, habitat, and other information for all breeding sites, for as many years as possible, from 1993 through 2007. This report provides data summaries in terms of the number of flycatcher sites and the number of territories. When interpreting and using this information, it must be kept in mind that a 'site' is a geographic location where one or more willow flycatchers establishes a territory. Sites with unpaired territorial males are considered breeding sites, even if no nesting attempts were documented. A site is often a discrete patch of riparian habitat but may also be a cluster of riparian patches; there is no standardized definition for site, and its use varies within and among states. For example, five occupied habitat patches along a 10-km stretch of river might be considered five different sites in one state but only a single site in another state. This lack of standardization makes comparisons based on site numbers problematic. Researchers for this report generally deferred to statewide summary documents or to local managers and researchers when delineating a site for inclusion in the database. However, to avoid inflating the number of sites and to establish more consistent definitions of the term 'site', adjacent and nearby sites from statewide reports were sometimes considered as a single site for the purposes of the rangewide data summary. Any combining or splitting of sites at the rangewide level was done on a case-by-case basis. Because of differences in site definitions, one should not evaluate the relative importance of a geographic region (such as drainage, watershed, or state) simply according to the number of flycatcher sites. A 'territory' is an exclusive defended area within a breeding site. Although detailed monitoring studies have identified unpaired territorial males and polygynous males at some flycatcher breeding sites, for the purposes of this report a territory is equivalent to the exclusive breeding area of a pair of flycatchers. In general, the concept of territory is more similar among states and different investigators than site; thus, it is a more robust unit to use for summaries and comparisons. However, note that the definition of a polygynous territory is not consistent among states; a male polygynously paired with two females would be considered one territory in some states and two territories in other states. For each site, we referred to reports or spoke directly with researchers and managers to gather information such as management entity/agency, location (state, drainage, elevation), gross habitat type (native, exotic, or mixed; dominant tree species), and number of flycatcher territories. Synthesizing the information on more than 200 breeding sites is challenging because annual data-collection and survey-reporting requirements are not standardized rangewide, and the nature and degree of readily available information varies widely from state to state. This is particularly true for areas such as California, where there are many flycatcher sites but surveyors are not required to submit standardized flycatcher survey forms. The lack of c

Open-File Report↗

USGS2007

The ecology of the Southwestern Willow Flycatcher in central Arizona - A 10-year synthesis report

BACKGROUND From 1996 to 2005, the U.S. Geological Survey (USGS) conducted a demographic study of the Southwestern Willow Flycatcher (Empidonax traillii extimus) in Arizona in collaboration with the Arizona Game and Fish Department (AGFD). The study was begun the year following the listing of the Southwestern Willow Flycatcher as an endangered species. At the time of the listing, very little was known about the biology and threats to the flycatcher, and one of the main objectives of the study was to gather detailed long-term information on the biology of the flycatcher. This report is organized into eight chapters. Following the introductory chapter, we deal with specific aspects of flycatcher ecology and habitat use in each of six separate chapters. We end with a concluding chapter that synthesizes information into broad topical themes that address key management issues. Each of the core chapters (chapters 2 through 7) conclude with a list of management considerations derived from the findings of the respective chapter.

Open-File Report↗

USGS2007

Southwestern Willow Flycatcher Breeding Site and Territory Summary - 2006

Introduction The Southwestern Willow Flycatcher (Empidonax traillii extimus) is an endangered bird that breeds only in dense riparian habitats in six southwestern states (southern California, extreme southern Nevada, southern Utah, southwestern Colorado, Arizona, and New Mexico). Since 1993, hundreds of Southwestern Willow Flycatcher surveys have been conducted each year, and many new flycatcher breeding sites located. This document synthesizes information on all known Southwestern Willow Flycatcher breeding sites. This rangewide data synthesis was designed to meet these objectives: * identify all known Southwestern Willow Flycatcher breeding sites, and * assemble data on population size, location, habitat, and other information for all breeding sites, for as many years as possible, from 1993 through 2006. This report provides data summaries in terms of the number of flycatcher sites and the number of territories.

Open-File Report↗