STICKLEBACK MALES, ESPECIALLY LARGE AND RED ONES, ARE MORE LIKELY TO NEST CONCEALED IN MACROPHYTES

Abstract Previous studies have shown (1) that stickleback males enjoy increased mating success when their nest is concealed, (2) that males reduce their courtship in the face of predation risk to a lesser extent when their nest is concealed, and (3) that eggs in concealed nests have higher hatching chances. Here we test the prediction that male sticklebacks prefer to establish a territory at a site with a macrophyte under which they can conceal their nest. We planted macrophytes at half of the potential nest sites at two depths, in a section of a channel in which sticklebacks naturally occur. Subsequently, we found significantly more nests with eggs at the sites concealed by macrophytes than at the control sites, suggesting that wild sticklebacks preferred to build their nests at sites that offer concealment. At the shallow depth, males occupying a site with a macrophyte were larger and redder than males at control sites, but not at the deeper level. This suggests that males of higher competitive ability and greater conspicuousness were more likely to settle at shallow sites where predation risk by the grey heron is high.