This week a Spotted Sandpiper (at least one) has been foraging along the Rouge River in Eliza Howell Park. Seeing it reminded me of how unusual this species is. Its mating system, polyandry, occurs in less than one percent of bird species.
(The photos are courtesy of Margaret Weber. )
Polyandry means the mating of one female with more than one male while a male mates with only one female. Spotted Sandpiper is the only polyandrous species I am aware of that breeds in Southeast Michigan.
There are some other members of the sandpiper family that have a similar mating system, but most sandpipers nest only in the very far north. The Spotted Sandpiper spends its summers in much of North America. (The range map is from the Cornel Lab of Ornithology. )
In the spring, the female arrives first and establishes a breeding territory before males arrive. When they do, she selects a mate and they prepare a nest together (on the ground). After the female lays eggs (usually 4), the male incubates them while the female selects another mate and repeats the process, perhaps up to 4 times (laying as many as 16 eggs).
Sometimes the female mates with only one male. In these cases, she participates in incubation and care of the young.
I see a Spotted Sandpiper most years in May, but have not yet seen evidence of them nesting in the park. The female and male look alike, so I don’t know if the Spotted I spotted is a female or male, don’t know if it is establishing its territory or just pausing on its way to a different breeding location.
Most of us have heard/used the “a rare bird” idiom. The Spotted Sandpiper is indeed a rare bird, being so different from most other birds in mating behavior.
It’s great to see part of the One Percent right here in Eliza Howell.