The unremarkable-looking spotted sandpiper is unique for one big reason: it’s often the females that arrive at breeding grounds first, mate with multiple males, and then split once the eggs are laid. The males do all the child-rearing in the sandpiper universe. The role reversal isn’t common, but it’s not entirely rare in nature either. Think: male seahorses, who carry their young, and certain amphibians. In other shorebird species—for example, jacana waterbirds and New Zealand kiwi birds—it’s also the females that are more dominant, larger, and in some cases, flashier.
When a female spotted sandpiper arrives from her wintering grounds in the coastal U.S., she immediately searches for a territory to stake out and defend—aggressively—from other females. Then, when male birds arrive on the scene, the females do the wooing. They use aerial displays, singing, and strutting to tempt up to four mates in one breeding season.
Because spotted sandpiper eggs are vulnerable to predation—females lay them on the ground, usually in open areas—it’s not unusual for the parents to lose half of the eggs. This is probably one reason why females practice polyandry: more mates means more eggs, to make up for the ones that she’ll inevitably lose. One record-setting bird in Minnesota holds the title for “the most number of eggs in the shortest amount of time”: five clutches with three males, in three-and-a-half months.
Spotted sandpiper nestlings are born fully feathered. They can run and find their own food within an hour of hatching. In a few hours, they can swim. Chicks, like their parents, move in a jerky, teetering motion. Ornithologists still don’t know the purpose of this wobbly way of moving around, but spotted sandpipers appear to teeter faster when they’re nervous, and stop the behaviour when they’re courting.