Next time youre doing some summer canoeing on the Connecticut, try this: ease your canoe over to the bank and paddle quietly downstream as you hug the shore. Before long, you will no doubt startle a robin-sized bird, which will lift off from a muddy bank with an awkward-looking, stiff-winged style of flight. After a short flight the bird may alight nearby, and you might be able to raise your binoculars for a closer look. If so, youll be looking at a dark-backed bird that continually bobs and dips as it picks invertebrates from the waters edge. In shape, it resembles the shorebirds that you normally associate with sandy beaches and pounding surf. Indeed, you are looking at a shorebird, albeit one that has diverged ecologically from the more coastal members of its family. Its the Spotted Sandpiper, Actitis macularia.
Most sandpiper species nest on Arctic tundra, but the Spotted Sandpiper breeds across a broad swath of temperate North America that includes the Connecticut River valley. The most unusual thing about the species, however, is not where it breeds but how it breeds. The Spotted Sandpiper has a polyandrous mating system, in which each female has several mates.
In a reversal of the pattern observed in the vast majority of bird species, female Spotted Sandpipers compete for access to males. Each female owns a breeding territory, which she defends vigorously from intrusions by other females. If a female successfully attracts a male to her territory, she will lay of clutch of up to 4 eggs in a scraped-out spot on the ground. After the clutch is complete, the female does not settle in to incubate the eggs. Instead, she leaves this chore to the male. The female is thus freed from the burden of incubating eggs and caring for offspring, and goes about the business of attracting one or more additional males, each of which will incubate and tend a clutch on the females territory. The female provides no care to her offpsring.
Both polyandry and sex-role reversal are quite unusual among birds, and its not yet clear why they arose in the Spotted Sandpiper. This little sandpiper does, however, remind us of an important principle of nature-watching. Even the most seemingly dull and inconspicuous inhabitants of the river can reveal fascinating stories if we have the patience to carefully observe them. The plain, brown Spotted Sandpiper, it turns out, has an exotic and mysterious mating system. Who knows what other fascinating phenomena might emerge from your observations at the river?