Spatial Variation in Clutch Size and Egg Size Within a Colony of Whiskered Terns (Chlidonias hybrida)

Abstract

Abstract Egg and clutch size of Whiskered Terns (Chlidonias hybrida) in relation to their location within the colony were investigated at Jeziorsko Reservoir, central Poland. All nests (n = 125) in the colony were individually marked and mapped using a Global Positioning System. Four nest clusters were distinguished within the colony based on the patchy distribution of floating vegetation which delineated potential nesting areas. Early breeding Whiskered Terns nested in more central and denser parts of nest clusters and late breeders nested in more peripheral zones of the clusters (trend analysis: F = 20.47, df = 1, P < 0.001). Pairs which nested closer to the centers of clusters had larger clutch sizes (trend analysis: F = 5.70, df = 1, P = 0.019), but there was no relationship between clutch size and distance to the colony center (F = 0.38, df = 2, P = 0.69). Edge clutches had higher coefficient of variation in egg volume in comparison to more central clutches (trend analysis: F = 5....