Intra-annual variations in abundance of Collared Plover Charadrius collaris in coastal French Guiana: the potential influence of rainfall, interspecific competition and breeding activities

The Collared Plover Charadrius collaris is a year-round resident in the Neotropics, mainly associated with inland habitats but regularly inhabiting seashores. Abundance patterns of some coastal populations in Brazil vary throughout the year indicating seasonal movements. Variability of food resources, seasonal competition with Nearctic migrants, and breeding activity are suspected reasons for these movements. Along the coast of French Guiana, the species is regularly observed on sandy beaches, but no monitoring had ever been conducted on these populations. We investigated intra-annual variations in abundance of Collared Plovers in the Kourou River estuary, French Guiana during 2004–2008. Along three sandy beaches near the city of Kourou, we counted Collared Plovers and the two most abundant Nearctic migrants, Sanderlings Calidris alba and Red Knots Calidris canutus. While conducting censuses we looked for evidence of breeding activity and extracted all local data available from the French Guiana wildlife database. Collared Plovers were found on sandy beaches from December to August, with a peak during the short dry season (mid-Feb–mid-Apr) that coincided with low abundances of Nearctic migrants. During the long dry season (Aug–Nov), plovers almost disappeared from sandy beaches, coinciding with the period of greatest abundance of Nearctic migrants, but also with the period of increased availability of suitable inland habitat. Periods of moderate abundance of both plovers and Nearctic migrants occurred during the two rainy seasons, which coincided with breeding activity of Collared Plovers being reported at inland habitats. Our data indicate that intra-annual abundance of Collared Plovers on the coast of French Guiana varies with rainfall patterns. Breeding activity in inland habitats and competition with Nearctic migrants may influence the observed abundance patterns in coastal areas, meriting further investigation.