A team of researchers tracked sandpipers throughout favored breeding sites and found that the males would often travel thousands of miles looking for mates. Competition for mating privileges is fierce and the tiny shorebirds are willing to fly great distances to look for willing females. The findings are in a paper that was just published in the journal Nature.
The pectoral sandpiper (Calidris melanotos) is a small shorebird that regularly migrates to find food and mating opportunities. The sandpipers are polygynous which means that males compete for females. Male pectoral sandpipers do not form monogamous pairs and don’t contribute any resources or offspring care. Instead, their goal is to mate with as many females as possible during breeding season. Females are only fertile for a few weeks at most. High levels of mating competition mean that most males won’t successfully court even a single female.
Scientists from the Max Planck Institute for Ornithology in Germany tracked pectoral sandpipers that were migrating to breeding grounds in northern Alaska and the Arctic tundra. In total, 100 individual males were tracked for the full duration of mating season. The team found that while the females stuck to specific areas, the males traveled throughout the entire breeding range. In many cases, the males traveled over 8,000 miles over the course of a month. Some males checked over 20 breeding sites in search of fertile females. This happened even when the male had already mated, showing that their goal is to mate with multiple females—even if it requires searching thousands of miles across the Arctic. Even after all this effort, most males failed to find mates. The team was surprised by this persistence, one of the most extreme examples in the animal kingdom.
Pectoral sandpiper males will fly for 8,000 or more miles in search of fertile, willing females. These extreme behaviors are the result of intense mating competition. The team notes that this nomadic behavior leads to a robust population without inbreeding or specialized adaptation to local environments.
Kempenaers, Bart and Mihai Valcu. Breeding site sampling across the Arctic by individual males of a polygynous shorebird. Nature (2017).