Mountain Plover Responses to Plague in Montana

Abstract

Plague is a bacterial (Yersinia pestis) disease that causes epizootic die-offs in black-tailed prairie dog (Cynomys ludovicianus) populations in the North American Great Plains. Through their grazing and burrowing, prairie dogs modify vegetation and landscape structure on their colonies in ways that affect other grassland species. Plague epizootics on prairie dog colonies can have indirect effects on species associated with colonies. The mountain plover (Charadrius montanus) preferentially nests on black-tailed prairie dog colonies and is thus negatively impacted by the loss of prairie dogs. We studied the effects of plague and colony spatial characteristics on the occupancy of 81 prairie dog colonies by nesting plovers in Phillips County, Montana, during a 13-year period (1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007). We used a robust design patch occupancy model to investigate how colony occupancy and extinction and colonization rates were affected by plague history, colony size, and colony shape. Here extinction and colonization rates refer to the probability that a colony loses/gains plovers in a subsequent nesting season, given that it had/lacked plovers in that breeding season. Colony occupancy was best explained by a model with no annual variation or plague effects. Colony extinction rates were driven by a combination of a quadratic of colony area, a 3-year plague response, and a measure of colony shape. Conversely, colonization rates were best explained by a model with a 4-year plague response. The estimated annual proportion of colonies occupied by plovers was 0.75 (95% confidence interval = 0.57-0.87). Estimated extinction probability ranged from a low of 0. Plague is a bacterial (Yersinia pestis) disease that causes epizootic die-offs in black-tailed prairie dog (Cynomys ludovicianus) populations in the North American Great Plains. Through their grazing and burrowing, prairie dogs modify vegetation and landscape structure on their colonies in ways that affect other grassland species. Plague epizootics on prairie dog colonies can have indirect effects on species associated with colonies. The mountain plover (Charadrius montanus) preferentially nests on black-tailed prairie dog colonies and is thus negatively impacted by the loss of prairie dogs. We studied the effects of plague and colony spatial characteristics on the occupancy of 81 prairie dog colonies by nesting plovers in Phillips County, Montana, during a 13-year period (1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007). We used a robust design patch occupancy model to investigate how colony occupancy and extinction and colonization rates were affected by plague history, colony size, and colony shape. Here extinction and colonization rates refer to the probability that a colony loses=gains plovers in a subsequent nesting season, given that it had=lacked plovers in that breeding season. Colony occupancy was best explained by a model with no annual variation or plague effects. Col...

Factors affecting Burrowing Owl occupancy of prairie dog colonies

“…prairie dogs were present at least once during the study period) (Figure 1). We defined ''colony'' as a specific patch on the landscape that was occupied by prairie dogs during !1 year beginning in 1995 (Dinsmore and Smith 2010). Owls nest from mid-May to mid-July in this region and often return to the same nest burrows year after year; in a similar study, .50% of the birds returned to within 200 m of their previous burrows (Poulin et al 2011).…”

“…Fish and Wildlife Service (USFWS, Charles M. Russell National Wildlife Refuge). This area was a mixedgrass prairie typified by flat-topped ridges dissected by shallow coulees and sagebrush flats (Dinsmore and Smith 2010). Within this area, we studied owls on black-tailed prairie dog colonies that were active (i.e.…”

“…New prairie dog colonies were created almost yearly; we attempted to survey them for prairie dogs and owls soon after they were established. The study area and prairie dog survey methods are described in greater detail in Dinsmore and Smith (2010).…”

“…We obtained two types of data from these two sources: (1) the area (in hectares) of each prairie dog colony and (2) Geographic Information System (GIS) coverage showing colony boundaries (Dinsmore and Smith 2010). To document plague history on the individual colonies, we relied solely on observational data from annual surveys of prairie dog colonies.…”

“…A complete mapping of all of the colonies was done in 1998, 2002, 2004, and 2007(Dinsmore and Smith 2010. For the other 8 yr, we obtained the measure of the colony areas in one of four ways, as described by Dinsmore and Smith (2010): (1) from an incomplete census of the colonies in the study area; (2) by extrapolating area from an estimated rate of change in a sample of one-third of all known active colonies in the study area; (3) by using the midpoint of colony area in adjacent years; or (4) from other additional sources (e.g., a plague event that eliminated a colony). Option 2 assumes that colony changes are correlated across years, and a correlation analysis of the 5 yr when all colonies were mapped showed that this was a valid assumption (Pearson correlation test, r ¼ 0.88).…”