The High-Elevation Population of Mountain Plovers in Colorado

Abstract

We surveyed a discrete population of Mountain Plovers (Charadrius montanus) in South Park, Park County, Colorado, to determine the size and relative contribution of this geographically isolated area to the global population of plovers. First, we mapped potential plover habitat within South Park based on landform and vegetation descriptors. Second, we identified occupied habitat using observations from a systematic inventory of potential habitat from 1995–1999 and from a study of breeding biology from 2000–2002. Third, we estimated breeding densities within a framework designed specifically for distance sampling. We mapped 82 750 ha of potential habitat. We recorded 2516 plover locations from which we estimated 29 176 ha of occupied habitat. We estimated densities for 14 960 ha of potential habitat. Average plover density from 2000–2002 was 7.9 ± 0.9 (SE) breeding adults km−2, a high value compared with other sites. We calculated a population of 1187 ± 140 (SE) plovers in the distance sampling area. Assuming density in our sampling area was similar for all documented occupied habitat, we estimated the population of plovers in South Park at 2310 adults. We conclude that South Park represents a contemporarily large concentration of breeding Mountain Plovers. Población de Altura de Charadrius montanus en Colorado Resumen. Estudiamos una población discreta de Charadrius montanus en South Park, condado de Park, Colorado, para determinar el tamaño y la contribución relativa de esta población geográficamente aislada a la población global de C. montanus. Primero, elaboramos mapas de los hábitats potenciales para C. montanus en South Park basándonos en descriptores de formas del paisaje y vegetación. Segundo, identificamos los hábitats ocupados por C. montanus utilizando observaciones de un inventario sistemático de hábitats potenciales realizado entre 1995 y 1999 y a partir de un estudio sobre su biología reproductiva realizado entre 2000 y 2002. Tercero, estimamos las densidades reproductivas utilizando una metodología específicamente diseñada para el método de muestreo con distancias. Elaboramos mapas de 82 750 ha de hábitat potencial. Registramos 2516 localidades en que se encontraron C. montanus, a partir de las cuales estimamos 29 176 ha de hábitat ocupado. Estimamos densidades para 14 960 ha de hábitat potencial. La densidad promedio de C. montanus desde 2000 hasta 2002 fue 7.9 ± 0.9 (ES) adultos reproductivos por km2, un valor alto en comparación con otras localidades. Calculamos una población de 1187 ± 140 (ES) individuos dentro del área censada con el método de muestreo con distancias. Asumiendo que la densidad en nuestra área muestreada fue similar en todos los hábitats documentados como ocupados, estimamos que la población de C. montanus en South Park es de 2310 adultos. Concluimos que South Park representa actualmente un área con alta concentración de individuos reproductivos de C. montanus.

Mountain Plovers in Oklahoma: distribution, abundance, and habitat use

“…The breeding density of Mountain Plovers in our study (0.36-0.62 birds/km 2 ) was lower than density estimates elsewhere in their range, including 6.0-9.0 birds/km 2 in Colorado (Wunder et al 2003), 1.22-8.41 birds/km 2 in Montana (Knopf and Wunder 2006), 0.0-5.9 birds/km 2 in Colorado (Knopf and Wunder 2006), and 4.47 birds/km 2 in Wyoming (Plumb et al 2005). The low density we observed may Vol.…”

“…We recorded separately the number of individuals detected at distances 0-200 m, 200-400 m, and >400 m from the observer. For density estimation, we used only those birds detected within 200 m (Wunder et al 2003), resulting in an effective sampling area of 25 ha (sum of four semicircular counts) per section. Because Mountain Plovers can be highly mobile, we were careful to avoid double-counting individuals at survey points within a section.…”

Making better sense of monitoring data from low density species using a spatially explicit modelling approach

“…Our estimates of detection rate were, in general, lower than those found elsewhere: 0AE94-0AE65 in Oklahoma, USA (McConnell et al 2009), 0AE38 in Colorado, USA (Wunder, Knopf & Pague 2003). The overall pattern in our results mirrored those of other surveys designed to increase the number of detections within sampling locations (e.g.…”

“…Numerous studies have recognized that mountain plovers are difficult to detect because they are cryptically coloured and often encountered in relatively low densities (Knopf & Wunder 2006). Past studies have accounted for detectability by using distance sampling (Wunder, Knopf & Pague 2003;Plumb, Knopf & Anderson 2005), markrecapture methods (Dinsmore, White & Knopf 2003), repeated visits (Dreitz, Lukacs & Knopf 2006;Tipton, Dreitz & Doherty 2008) and removal methods (McConnell et al 2009;Tipton, Doherty & Dreitz 2009).…”

“…Our study and that of Dreitz, Lukacs & Knopf (2006) both used a multiple revisit method of sampling and similar statistical methods. Plumb, Knopf & Anderson (2005) and Wunder, Knopf & Pague (2003) used distance sampling which requires a different sampling strategy and different statistical approach. Finally, McConnell et al (2009) used a point count sampling approach and post hoc detection correction method, and Tipton, Doherty & Dreitz (2009) used a probability based sampling approach and a design based method of deriving abundance.…”