Selection Indicates Preference in Diverse Habitats: A Ground-Nesting Bird (Charadrius melodus) Using Reservoir Shoreline

Abstract

Animals use proximate cues to select resources that maximize individual fitness. When animals have a diverse array of available habitats, those selected could give insights into true habitat preferences. Since the construction of the Garrison Dam on the Missouri River in North Dakota, Lake Sakakawea (SAK) has become an important breeding area for federally threatened piping plovers (Charadrius melodus; hereafter plovers). We used conditional logistic regression to examine nest-site selection at fine scales (1, 3, and 10 m) during summers 2006–2009 by comparing characteristics at 351 nests to those of 668 random sites within nesting territories. Plovers selected sites (1 m2) that were lower than unused random sites, increasing the risk of nest inundation. Plovers selected nest sites that were flat, had little silt, and at least 1 cobble; they also selected for 3-m radius nest areas that were relatively flat and devoid of vegetation and litter. Ninety percent of nests had <38% coverage of silt and <10% slope at the site, and <15% coverage of vegetation or litter and <31% slope within the 3-m radius. Gravel was selected for at nest sites (11% median), but against in the area 10-m from the nest, suggesting plovers select for patches or strips of gravel. Although elevation is rarely evaluated in studies of ground-nesting birds, our results underscore its importance in habitat-selection studies. Relative to where plovers historically nested, habitat at SAK has more diverse topography, substrate composition, vegetation communities, and greater water-level fluctuations. Accordingly, our results provide an example of how habitat-selection results can be interpreted as habitat preferences because they are not influenced by desired habitats being scarce or absent. Further, our results will be useful for directing habitat conservation for plovers and interpreting other habitat-selection studies.

Habitat selection and movements of Piping Plover broods suggest a tradeoff between breeding stages

“…Habitat selection within available brood-rearing area Grid cells within available brood-rearing areas were classified into nine categorical combinations of vegetation coverage (0-30, 30-50, [50 %) and slope (0-10, 10-20, [20 %; see Anteau et al 2012bAnteau et al , 2014a. We defined used habitat for each brood location as the vegetation coverage estimate made at the time of the observation in the field and calculated the slope from the DEM.…”

“…Traditional analyses used for discrete choice or conditional logistic regression (e.g., Cooper and Millspaugh 1999;Manly et al 2002;McDonald et al 2006;Anteau et al 2012b) were not feasible for these data because of the nested sources of variability, namely, characteristics within the 2-day interval habitat-choice sets were nested within those of landform, CLUSTER, and brood age. Accordingly, we examined differences in habitat features between those of used habitat (mean value within a 10-m radius around the observation) and the mean values of habitat features within the interval specific habitat-choice sets with a multivariate analysis of variance [MANOVA (multivariate analysis of variance); PROC GLM; SAS Institute 2002].…”

“…It has been proposed that avian species producing precocial young select breeding habitats based on factors related to successful nesting and rearing of chicks (e.g., Blomqvist and Johansson 1995;Pöysä et al 2000;Anteau et al 2012b). Precocial chicks require habitats which provide both sufficient forage to meet the increasing energy requirements of growth and development and adequate cover for protection from exposure to bad weather and to hide from potential predators.…”

“…Available habitat at SAK is diverse and comprises all or most of the characteristics the species encounters in other habitats throughout its breeding range (e.g., river sandbars, linear beach shorelines; Anteau et al 2012b); therefore, evaluation of habitat selection and movements by broods at SAK provided us with an opportunity to describe broodrearing habitat preference (Johnson 1980;Robsertson and Hutto 2006;Anteau et al 2012b). Preferred nesting habitat at SAK has been described by Anteau et al (2012b), and Anteau et al (2012a) proposed a potential ecological trap at SAK based on nest-site habitat selection preferences that led to an increased risk of nest inundation at the reservoir.…”

“…Preferred nesting habitat at SAK has been described by Anteau et al (2012b), and Anteau et al (2012a) proposed a potential ecological trap at SAK based on nest-site habitat selection preferences that led to an increased risk of nest inundation at the reservoir. Anteau et al (2014c) found fledging rates to be lower on island versus mainland habitats and that chicks which moved farther distances during the brood-rearing period also exhibited slower growth rates at SAK.…”