By: Chris Elphick @ UConn
How many are there? It seems like a simple question. From a conservation standpoint, knowing the size of a population is central to deciding how rare a species is, how vulnerable it is, and what level of protection it needs. Quantifying population size, however, is fraught with difficulty, especially for species that live over broad geographic areas, that move around a lot, and that like to hide in dense vegetation … all characteristics of the birds that we study.
Nonetheless, when we began the Saltmarsh Habitat and Avian Research Program, one of our fundamental goals was to figure out the abundance of tidal marsh specialist birds throughout the northeast and mid-Atlantic region. Those numbers have now been published in The Condor: Ornithological Applications (Wiest et al. 2016). Our estimates are based on visits to 1780 survey points distributed across 582 patches of marsh habitat from Virginia to Maine. Survey points were chosen using a randomized selection process designed to ensure that they are representative of all marshes in our study area, thereby allowing us to extrapolate and estimate population numbers across the entire region.
At the time of our surveys in the summers of 2011-12, we estimate that there were approximately 151,000 clapper rails, 117,000 willets, 5,000 Nelson’s sparrows, 53,000 saltmarsh sparrows, and 230,000 seaside sparrows within our study region. The breeding range of saltmarsh sparrow lies almost entirely within our sampling region so our estimate of 53,000 birds is likely to be close to the global population size of this declining species. The other species, however, also breed outside of the northeastern US, so our numbers are not global estimates. To fully assess the population sizes for these species, we would need to replicate our survey in coastal marshes along the Atlantic Coast of the southeastern US and along the Gulf Coast.
This new paper is the first of several that we are working on that emanate from our original US Fish and Wildlife Service (USFWS) State Wildlife Grant. To see the report from that project, along with data summaries for each state, go here. None of our work would be possible without the support of the USFWS, the North Atlantic Landscape Conservation Cooperative, the Northeast Association of Fish and Wildlife Agencies, the National Science Foundation, and many other partners. Many field technicians also spent hundreds of hours slogging through the marshes of the Atlantic coast to collect the mass of data that boils down to 5 population estimates – without their hard work, our simple question would remain unanswered.
Wiest, WA, MD Correll, BJ Olsen, CS Elphick, TP Hodgman, DR Curson, and WG Shriver. 2016. Population estimates for tidal marsh birds of high conservation concern in the northeastern USA from a design-based survey. The Condor: Ornithological Applications 118:274-288.