Nest-Site Selection and Reproductive Success of the Western Snowy Plover in Kansas
Authors:   , Sexson Matthew 
Published: February 2023

The Western Snowy Plover (Charadrius alexandrines nivosus) is a small (approximately 46 g) shorebird that nests and forages along North American beaches, wetlands, river sandbars, and lake shores. Migratory populations of Western Snowy Plovers are distributed along the Pacific coast and at inland sites occurring east and west of the Rocky Mountains. Resident populations of Western Snowy Plover occur on the Gulf Coast of Mexico and Texas (American Ornithologists' Union 1998). Population data suggest that Western Snowy Plover numbers are declining throughout North America: a similar decline is suspected in populations in Kansas (Page, et. al. 1995, Busby 2003). As such, the species was listed as threatened in the state in 1987. In addition, critical habitat was designated at Quivira National Wildlife Refuge (NWR), Cheyenne Bottoms Wildlife Area (WA), and on the Kansas portions of the Cimarron River. Due to the current status of the Western Snowy Plover in the Midwest, information regarding habitat requirements, habitat use, and, when possible, reproductive success are valuable in guiding management and conservation activities at state and regional scales. In 2005, I located and monitored a total of263 Western Snowy Plover nests al Quivira NWR (n = 232) and Cheyenne Bottoms WA (n = 31). Of these 263 nests, 27.4% had eggs that hatched, 25.9% were flooded, 7.6% were abandoned, 7.2% were depredated, and 0.7% were lost to human disturbance. The fate of31.2% of the nests was unknown. After hatching, I attempted to monitor chicks until first flight. At the conclusion of the breeding season, nest site characteristics such as nest substrate and surrounding vegetation were surveyed using a 1-m2 quadrat centered on each nest, and paired random sites. A total of 162 Western Snowy Plover adults and chicks were captured and banded. Two individuals, a chick captured alone day old at Quivira NWR, and an adult captured while incubating a nest at Quivira NWR, were sighted in 2006 at wintering locations on the Texas coast of the Gulf Coast. In addition, two adult females initiated second nests within the 2005 breeding season, with one potentially representing the first documented case of double brooding among individuals at inland sites east of the Rocky Mountains. Finally, as of 17 April, five individuals, adults banded at Quivira NWR in 2005, have been sighted at Quivira NWR in 2006. To investigate the characteristics of nest sites, descriptive data from nest and random quadrats were analyzed for differences using a series of Mann-Whitney U tests, following a Bonferroni correction. In addition, nests that successfully hatched at least one egg were statistically compared to nests that did not. The success of nests, under varying conditions such as extreme temperature and precipitation, threat of predation, threat of human disturbance, and threat of flooding were analyzed using randomization, a re-sampling technique. I detected significant differences between nest quadrats and random quadrats with respect to the percentage of salt, soil, sand, gravel, and rock substrate types. In addition, I detected a significant difference between nest sites and random sites with respect to vegetation height. Nest sites and random sites were not significantly different when comparing percent vegetative coverage surrounding the nest. When comparing nest quadrats at nests that hatched at least one egg to unsuccessful nests. I did not detect a significant difference with respect to the proportion of salt, soil, sand, and rock. However, a marginally significant difference was detected with respect to the proportion of gravel substrate, as nests that were successful had a greater proportion of gravel than unsuccessful nests. In addition, a significant difference was not detected between successful and unsuccessful nests with regard to percent vegetation and mean vegetation height. Nests that were located on artificial nest pads in 2005 were flooded significantly less than expected at random. In addition, nests that were located within an electric predator control fence were depredated less often than expected at random. Nests located where human disturbance was more probable were also significantly less successful than expected at random. However, extreme precipitation and temperature did not significantly affect nest success. Various management practices at Western Snowy Plover nesting areas can encourage nest success (Koenen et al. 1996). Some hypothesize that the speckled egg of the Western Snowy Plover can be cryptic, and relatively less detectable by predators, when on a substrate of varying size and color (Meyer 2005). Providing potential nesting areas that maximize gravel substrate types, and minimize homogenous landscapes of soil or mud, could encourage nest success through egg crypsis. In addition, nest substrate that is relatively large in size, such as gravel or rock, might provide the means by which precipitation can be efficiently shed away from the nest, as opposed to being absorbed by sand or soil, potentially flooding the nest or limiting the maintenance of clutch temperature. Furthermore, predator control fences and elevated nest pads or ridges can be used to reduce the effect of terrestrial predators and flooding on nest success (Koenen et al. 1996; Mabee and Estelle 2000). Finally, human disturbance, which can cause significant nest loss, as well as overall habitat degradation, can be reduced through interpretive signage near nesting areas, or overall public exclusion (Ruhlen et al. 2003).