The Grebe and the Mallards

by Carl Strang

For more than a week, a migrating pied-billed grebe stayed on May’s Lake in late November.

This bird was constantly in the company of a group of mallards. Even when the ducks were standing on fallen logs near shore, the little diving bird floated close by. Here the grebe is at the far edge of a feeding mallard group.

The ducks were diving for aquatic plants. Mallards are not very good divers. The splash in the following photo is characteristic of their inefficient plunges.

They stayed beneath the surface 3-5 seconds, which in the relatively shallow water was enough for them to acquire a snack. If I were a children’s book author, I might be inspired to write a story about how the grebe was lonely, made friends with the ducks, then taught them how to dive for food in exchange for their companionship. While that story has emotional appeal, I’m pretty sure none of it was taking place.

Notice how two of the mallards are taking a peek below the surface before diving. The area where they are feeding is only a little farther out from depths where they can get food by tipping up. Mallards don’t dive often, but do so occasionally when bathing or when chasing one another. I’m pretty sure the ducks would be diving for food even if the grebe weren’t with them.

So what of the grebe’s behavior? This is a fairly solitary species, except during the breeding season. They don’t travel in flocks, or even family groups. Young make their way south on their own, entirely by instinct. Nevertheless, a grebe wanting others to hang out with could find them, and wouldn’t need to affiliate with ducks (grebes are now known to be more closely related to flamingos than to ducks, thanks to genetic comparisons made at the Field Museum).

Pied-billed grebes frequently can be seen in the vicinity of flocks of diving ducks or coots on larger lakes during migration, and my impression is that this is more than a random association, though some grebes also are off by themselves. I think the affiliation probably is more like what we see in mixed flocks of migrant songbirds than a social expression. There is evidence that mixed flocks have two advantages for their members. First, they provide more sets of senses for detecting the approach of predators (and the lucky bird that first spots such an approach can place itself on the far side of the flock). Second, the activity of so many birds foraging in close proximity stirs up prey which may escape the individual that first flushed it, but then can be caught by one of the others. It seems likely to me that something like this is going on with the grebes, too.

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