Researchers study the endangered sparrow and its habitat to provide data to aid recovery efforts.
|A population in decline: Florida grasshopper sparrow numbers continue to decrease for unknown reasons.
The next few years will be crucial for the Florida grasshopper sparrow, a critically endangered bird whose numbers have inexplicably declined. Point count surveys in 2012 detected only 75 singing males, down from 233 counted four years earlier. Even after accounting for imperfect detection of this cryptic sparrow and including remnant populations on private lands, fewer than 500 individuals may remain. Scientists and land managers are unsure of the cause of the decline. According to land managers, prairies on public lands managed for the sparrow appear the same as 30 years ago, when the bird’s population seemed to be more stable.
The rate of the sparrow’s decline is cause for concern, making recovery efforts especially important. Members of the FWC’s Florida Grasshopper Sparrow Working Group coordinate emergency efforts with other members, including: the Florida Department of Environmental Protection; U.S. Fish and Wildlife Service; Avon Park Air Force Range; University of Florida; University of Central Florida; Archbold Biological Station and Tall Timbers Research Station.
Biologists monitor Florida grasshopper sparrows each year during the breeding season, April through June, at survey stations on public lands. They listen for singing males establishing territories and look for perched Florida grasshopper sparrows. By using consistent sampling methods, these population indices provide a relative estimate of population size and trends over time. In addition to annual monitoring, two new research projects lead by FWC biologists will begin in 2013 and 2014 (see details below). Researchers and managers will use the results of these projects to identify limiting population factors and evaluate management actions.
|Female Florida grasshopper sparrow with new color bands.
Nesting and Disease Study (2013-2015)
This research will take place during three breeding seasons at the Three Lakes Wildlife Management Area in Osceola County. The objectives for this study are to generate robust life-history parameters, including estimates of pairing success, nest survival rates, as well as fledgling and adult survival. These parameters can then be used to identify the stages in the bird’s life cycle that are currently limiting population growth. Once identified, future research and management actions can be developed to prioritize the enhancement of these stages.
By color-banding birds in the study area, we will also be able to generate data on individual movements when birds are sighted in new areas. This information can be used to help understand decisions birds make when deciding where to establish territories in relation to land management treatments, such as prescribed burns.
Update after the 2013 season: The first field season of this project was a success. A total of 42 males, five females and 10 juveniles were newly color banded during 2013. Six of 7 adult males color banded during the 2012 season were sighted again in 2013. Although they are generally described as a sedentary subspecies, the birds displayed many extraterritorial movement events ranging from 0.2-2.7 km. Despite a very low mean nest survival estimate, Florida grasshopper sparrows demonstrated a propensity for repeated nesting attempts. This season we observed a pair that produced at least three successful nests. Fecal samples from 16 birds were collected and analyzed for the presence of disease organisms. Seven of these samples were tested for intestinal parasites, nine samples for the presence of salmonella, and five for acid-fast bacteria (such as aviantuberculosis). These samples were all negative for disease.
Grassland Bird Nest Camera Study (starting spring 2014)
Conducting research on nest predators using video surveillance systems is a priority for 2014. It is very difficult to accurately assign specific nest predators using traditional nest monitoring visits. A recent grant from the U.S. Fish and Wildlife Services (USFWS) will aid FWC researchers at ThreeLakesWildlife Management Area to build and deploy video surveillance systems at the nests of surrogate ground-nesting grassland birds such as Bachman’s sparrows and eastern meadowlarks. Information on the predator community from these nests will guide future management aimed at increasing nest success rates.
Audio - songs of the Florida grasshopper sparrow