Wednesday, October 31, 2018

Surveying Birds in Arizona's Uplands

Feral burros. Photo by Lauren Harter
Early in the spring of 2018, we conducted the first season of Arizona Uplands surveys, a project with Arizona Game & Fish as part of a larger study on the impacts of feral burros (donkeys) on Arizona wildlife and ecosystems. Burros were imported to Arizona as early as the 1600s, and eventually established feral populations as they escaped or were abandoned by prospectors in the 1800s. Equids have a different tooth structure than native ungulates, so can have heavy impacts on native vegetation that have evolved for approximately 10 thousand years in their absence. Feral burros can also compete with, and in many cases outcompete, native animals for food and water sources. As such they are the focus of management and study by federal and state agencies. Our goal with these bird surveys is to investigate the impact of burros on breeding bird populations.

Surveys were conducted in two areas, the Havasu Herd Management Area in western Arizona and the Lake Pleasant Herd Management Area north of Phoenix. We surveyed 60 plots in each area, with plots including areas with and without burros, with and without surface water, and other variables taken into consideration.

Over the course of the season in these 120 surveys, we documented a total of 128 bird species. Surveys took us to new areas for all five seasoned surveyors, from Lake Pleasant; Castle Hot Springs; and flats around Wittmann; to the Bill Williams River; Cactus Plain, Buckskin, and Needles wilderness areas; and the difficult to access Mohave Mountains. Once we have obtained a few more years of data, we hope to be able to inform future burro management based on good science.

- Lauren

Wednesday, June 27, 2018

In Search of the Elusive Desert Thrashers

Walking through thrasher country.  Photo by Michelle Tobin

Bendire's Thrasher, Jen Tobin
The Desert Thrasher Survey season began this year at the end of March and just wrapped up a few weeks ago in mid-June. Nevada’s team is part of a larger network of governmental agencies, non-profits, and volunteers (The Desert Thrasher Working Group, DTWG). The DTWG is dedicated to improving our understanding of these enigmatic Thrashers, and recently has developed a standardized survey protocol for these birds. After much deliberation the DTWG decided on an area search survey approach, creating survey plots 300x300m to be surveyed within 40 minutes. This protocol was based off of surveys conducted by Point Blue Conservation Science. By conducting practice surveys we believed that at this size within a desert landscape the surveyor should be able to detect a thrasher on the plot and survey multiple plots in one morning/field day. To allow for variation in detection as well as arrival times for Bendire’s thrashers (Le Conte’s thrashers are a non-migratory species) we decided to survey each of our plots three times during the breeding season.

The 2018 surveys spanned the entire known U.S. range of the LeConte’s and Bendire’s thrashers. Surveys were conducted in Arizona, California, Nevada, New Mexico, and Utah. Approximately, 450 plots were surveyed across these states.

Le Conte's Thrasher nest. M. Tobin
In total Nevada surveyed 126 plots:112 which were part of the region-wide survey effort, 12 were exploratory surveys, and 6 plots were revisits to areas where thrashers were found last season. As part of the survey protocol each of the 118 plots (112 region-wide and 6 resurvey plots) plots were surveyed three times throughout the season. Due to time constraints the exploratory plots could only be surveyed two times during the season. Therefore, our total survey effort for the season was 378 surveys.

In addition, to surveying for birds on each plot habitat assessments were also conducted at the plot center. We used a point center quarter method to evaluate the habitat. In addition, we recorded information on fruit-bearing shrubs, Yucca species, ground cover and composition, and measures of disturbance and invasive species.

In 2018, in Nevada, we also began our adopt-a-thrasher program. This program was designed so that volunteers could revisit known Bendire’s Thrasher territories and document presence/absence of this species. We focused specifically on Bendire’s thrashers, because this species has been very difficult to capture on surveys, and multiple questions still remain about the basic life history, phenology, and occurrence of this thrasher.

Le Conte's Thrasher nestlings, Jen Tobin.
We are currently in the process of entering all our data from the season, but preliminary numbers suggest that our thrasher counts are higher than last season. We recorded at least 16 observations of Bendire’s thrashers this year, which appears to be double the number we observed in 2017. For LeConte’s thrashers, to date, we have entered 165 records for these birds. However, this represents multiple visits to plots and therefore could be an inflated number of actual territories. We hope to finish up data entry by the end of June, and have more concrete numbers and an analysis of our habitat data by the end of the summer.

 - Dawn

Wednesday, February 21, 2018

Surveying birds in Arizona grasslands

Central Arizona grassland.
Last year, we began working with our partners at the Arizona Game and Fish Department on grassland bird surveys in spring, summer, and fall. The state of Arizona has several programs aimed at restoring historical grasslands across the state, with the goal of improving habitat for wildlife such as pronghorn as well as improving rangeland. The main purpose of our surveys was to understand how these ongoing grassland treatment activities are affecting breeding birds. For bird surveys, the AZGFD also partnered with the Bird Conservancy of the Rockies to use their Integrated Monitoring in Bird Conservation Regions (IMBCR) program. We started the season in central and northern Arizona, covering both public and private land across Yavapai and Coconino counties. In July and August, once the monsoon rains began to fall, we moved to southeastern Arizona. There, we surveyed ranches in Graham, Cochise, Santa Cruz, and Pima counties.  

Pronghorn kept us company on some surveys.
In central and northern Arizona, surveyed habitats ranged from high desert grasslands sprinkled with acacia and prickly pear, to rolling hills of pinyon-juniper, to prairie dog-dotted flats. Thrashers were particularly interesting in this region. Crissal Thrashers were common throughout, and we found quite a few Bendire's Thrashers (one of our focal species on our thrasher project) in open juniper-barberry woodland east of Flagstaff. We even turned up a very rare Brown Thrasher near camp in the same area! In southeastern Arizona, most of our surveys were in semidesert grassland, in both the Sonoran and the Chihuahuan deserts. Here we were serenaded by the cascading songs of Cassin's Sparrows on nearly every survey, as well as the bouncing-ball song of Botteri's Sparrows and of course the ubiquitous Black-throated Sparrow. In a few pure grassland sites, we recorded the very local breeding Grasshopper Sparrow. In July, we enjoyed watching the monsoons build over the mountains almost every day, but were only caught in a few downpours!

We're looking forward to continuing and even expanding this monitoring effort to increase our understanding of grassland birds in Arizona this year!

We kicked off our southeastern Arizona grassland surveys in mid July with some beautiful scenery