For many years Western Grebes and Clark’s Grebes were considered to be color phases of the same species. But when it was discovered that they practice preferential mating (a strong tendency to only mate with their “own kind” – Western x Western and Clark’s x Clark’s) they were classified as two distinct species. DNA studies reinforce this decision.
The two species are similar but easily distinguished from each other by several field marks.
The eyes of Western Grebes are surrounded by black and their bill is dusky or yellow-green and less brightly colored than that of the Clark’s Grebe.
The eyes of Clark’s Grebes are surrounded by white and their bill is bright yellow to orange-yellow.
Both species are common in my area and I’ve spent years photographing them and observing their behaviors. During the breeding season it’s relatively easy to single out mated pairs based on a variety of well-known behaviors that occur between paired birds.
One of the behaviors that occurs between mates is called “mate feeding”. This is where the female repeatedly begs for food from the male while he is on the water’s surface. When the male catches a fish he gives it to her and then almost immediately dives for another. The begging of the female stops while he is under water.
I observed and photographed the following behavior a few days ago at Bear River Migratory Bird Refuge.
This mated pair consists of a male Clark’s Grebe on the right and a female Western Grebe. Here the male is delivering a fish to the female…
which she immediately takes…
and gobbles down.
A few minutes later he delivered another fish.
And another. I watched this happen 5-6 times over the course of about 20 minutes.
In the years I’ve watched and photographed the behaviors of both species I’ve never before seen a Western Grebe mated to a Clark’s Grebe. Mixed species pairs are uncommon to rare so to have seen this natural but unusual behavior was pretty special for me.
You just never know what you’re going to see “out there” if you pay attention…