Hydrology, habitat change and population demography: an individual‐based model for the endangered Cape Sable seaside sparrow Ammodramus maritimus mirabilis

Abstract

Summary 1.Habitat destruction and fragmentation have led to precipitous declines in a number of species of concern. For these species, traditional models that group individuals into age or stage cohorts may not accurately capture the stochasticity associated with small populations. Additionally, traditional models do not explicitly incorporate landscape-level structure, which becomes increasingly important at small population sizes. Thus, for declining species, spatially explicit individual-based models (SEIBM) can be used to understand both population demography and the impacts of habitat destruction, and to guide management practices to increase the chances of species survival. 2. To gauge the impacts of changes in habitat and also demographic rates on a US endangered species, we constructed an SEIBM for the Cape Sable seaside sparrow ( Ammodramus maritimus mirabilis Howell) of the South Florida Everglades. The model simulates temporal and spatial dynamics of individual sparrows using local GIS-based topography, vegetation and hydrology along with behavioural and demographic rates derived from field studies. 3. When adult mortality and, to a lesser extent, juvenile mortality were increased in model simulations, there was an increase in extinction risk and a decrease in population size, whereas changes in number of clutches or female mating range had little impact. In contrast to the effects of simulating changes in mortality rates, simulated landscape-level changes (increasing water levels or decreasing habitat availability) were associated with dramatic population declines and increases in extinction risk. The sparrow appears to be particularly sensitive to the loss of higher-elevation breeding habitat. These results highlight the importance of proper water-and land-use management in assuring the species' survival. 4. Synthesis and applications. Although changes in demographic rates affect population growth and are often the focus of conservation efforts, changes in habitat structure can also dramatically alter population viability. When both landscape-level and demographic data are available, spatially explicit models are particularly advantageous. Not only do they allow researchers and resource managers to prioritize areas for habitat restoration and species management, but they can also be used to help focus future research efforts.

Adult and Juvenile Survival of Black-Capped Vireos Within a Large Breeding Population in Texas

“…Population projection models are used to predict population growth rates, the likelihood of extinction, and to assess different management alternatives, especially for endangered species (Heppell et al 1994, Walters et al 2002, Elderd and Nott 2008. Because population dynamics can be sensitive to even small changes in fecundity and survival (Lande 1988, Ryan et al 1993, Woodworth 1999, accurate estimates of these parameters are necessary for projection models to yield reliable predictions (Beissinger andWestphal 1998, Anders andMarshall 2005).…”

Fire disturbance influences endangered Cape Sable Seaside Sparrow (Ammospiza maritima mirabilis) relative bird count

“…Restoration success requires an understanding of the factors affecting ecosystem and wildlife population health (Hobbs & Harris, 2001;Ruiz-Jaen & Aide, 2005), including the effect of disturbance. In the Everglades, the Cape Sable Seaside Sparrow (CSSS; Ammospiza maritima mirabilis) is strongly associated with, and a key indicator of, marl and mixed marl prairie communities (Elderd & Nott, 2008;Lockwood et al, 2001). The CSSS is federally endangered (U.S. Fish and Wildlife Service, 1999), non-migratory, endemic to south Florida, and restricted to freshwater prairies of Everglades National Park (ENP) and Big Cypress National Preserve (BICY).…”

“…Fish Target audience: Conservation and restoration practitioners, managers, and scientists and Wildlife Service, 2016). Marl prairie community is located in short-hydroperiod areas inundated for 4-6 months out of the year, often dominated by muhly grass (Muhlenbergia filipes; Elderd & Nott, 2008), and supported by intermediate disturbance, such as fire, drying, and flooding (Kushlan et al, 1982). The CSSS nests at a preferred mean vegetation height of 14-18 cm (Lockwood et al, 1997;Werner, 1975), and nests are often lost to predators (e.g., small mammals; Baiser, Boulton, & Lockwood, 2008) when water levels rise above approximately 15 cm (Lockwood et al, 1997;Lockwood et al, 2001), making the timing of high water levels important, especially for egg survival and fledging success (Lockwood et al, 1997;Werner, 1975).…”

Computational population biology: linking the inner and outer worlds of organisms

“…Generally the properties of these tracks were expressed in terms of the distributions of step sizes and shifts in the directions of consecutive steps (Benhamou 2004, Edwards et al 2007), and comparisons of these data with uncorrelated or correlated Gaussian and Lévy walks (Metzler and Klafter 2000, Edwards et al 2007, Getz and Saltz 2008, Duffy 2011) or mixed-distribution walks (Morales et al 2004, Fryxell et al 2008). More recently individual movement has been related to structures on real landscapes (Gough and Rushton 2000, Clark et al 2001, Harper et al 2002, Macdonald and Rushton 2003, Wiegand et al 2004, Bar-David et al 2005, Bar-David et al 2008, Elderd and Nott 2008), as well as and the presence of other organisms on the landscape (Getz and Saltz 2008, Willems and Hill 2009). In particular conspecifics influence the movement of individuals through herding, mating, and territoriality, while heterospecifics influence movement through foraging behavior, territoriality or predator avoidance, where the latter has been expressed in terms of the so-called “landscape of fear” (Laundre et al 2001, Willems and Hill 2009, Laundre 2010).…”