FACTORS AFFECTING INTERANNUAL MOVEMENTS OF SNOWY PLOVERS

We studied the interannual movements of 361 individually color-banded adult Snowy Plovers (Charadrius alexandrinus nivosus) at Great Salt La ke, Utah from 1990 to 1993. In northern Utah, Snowy Plovers nested in a dynamic environment; suitable breeding habitat declined by 50% at tw o study areas in four years. Male Snowy Plovers were more site faithfu l than females; 40% of males exhibited fidelity compared with 26% of f emales (P < 0.01). However, as the amount of available suitable nestin g habitat declined, male site fidelity diminished, whereas female fide lity remained relatively constant. We found strong evidence that femal e site fidelity was affected by nesting success in the previous year. Females that nested unsuccessfully were less likely than successful fe males to exhibit site fidelity the following year; males did not exhib it this nest-success bias. In addition, unsuccessful females breeding at sites with high densities of nests tended to disperse the following year, whereas male site fidelity did not appear to be affected by eit her a study site's overall nesting success the previous year or a stud y site's nest density the previous year. Female avoidance of areas wit h high densities of nests may be an antipredator strategy. Snowy Plove rs in northern Utah have biparental incubation duties, but only males care for broods. Familiarity with brood-rearing areas Mas one plausibl e explanation for male-biased fidelity. However, we could not eliminat e an alternative hypothesis that both focal study sites represented sc arce breeding areas due to the presence of freshwater, and male Snowy Plovers preferred to use the same areas rather than disperse. We propo se that more landscape-level studies are needed to address questions c oncerning local and regional movement patterns.