Life History
Western grebe (Aechmophorus occidentalis) and Clark's grebe (A.clarkii)
Grebes are diving birds that have adapted to life in and on the water over millions of years. All grebes (there are five genera worldwide) have highly reduced wings (especially during nesting season when they molt flight feathers). They often congregate in rafts and nest in colonies.
PAS monitors and advocates for Aechmophorus grebes: Western and Clark's. The Western grebe and Clark's grebe were once thought to be different color phases of the same species, and have only recently been determined to be different species of the same genus.
Aechmophorus grebes spend almost their whole lives on the water and, because of their adaptations to swimming, can barely walk on land. Their legs are far at the back of the body and provide poor balance. Grebes are much more graceful, agile, fast, and at home on the water, as seen in the video below.
PAS monitors and advocates for Aechmophorus grebes: Western and Clark's. The Western grebe and Clark's grebe were once thought to be different color phases of the same species, and have only recently been determined to be different species of the same genus.
Aechmophorus grebes spend almost their whole lives on the water and, because of their adaptations to swimming, can barely walk on land. Their legs are far at the back of the body and provide poor balance. Grebes are much more graceful, agile, fast, and at home on the water, as seen in the video below.
MigrationGrebes migrate from coastal waters in the spring to inland lakes for nesting. Lakes here in the Intermountain West support a large percentage of nesting grebes, and therefore were chosen for surveys to improve breeding conditions. Fall migration occurs sometime between October and December when grebes fly back to ocean habitats.
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Courtship
Aechmophorus grebes engage in some of the most beautiful and complex courtship rituals of any birds. They swim together, displaying for each other in many different ways. This often involves presenting vegetation to each other, giving food to one another, and culminates with a rushing display. This is where both birds simultaneously raise up and run across the water side by side for up to 150 feet, then dive together. These displays can be seen anywhere Aechmophorus grebes nest, as they always perform these rituals prior to and during nesting. See video to the right.
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Nesting
Grebes build floating nests connected to emergent or submerged vegetation. These nests can be vulnerable, but are a compromise in adaptation. The nests can be stranded on dry land as water levels decline through the summer, especially on lakes managed for power production or downstream rights.
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Young
Grebe adults "back brood" young as soon as they hatch. Once young have hatched, they climb on the adults' backs and head to open water, never returning to the nest. They spend the remaining part of summer being fed by parents and learning to swim and dive, until it is time to migrate to the coast.
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Diet
Grebes are piscivorous, or fish eating, and dive in pursuit of prey in both salt and freshwater. Studies have shown Western and Clark's grebes are able to consume up to a pound of fish each day. When you consider the size of the fish, most often minnows about 2-4 inches long, this is quite a large number of fish each day.
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Species Differences
Western and Clark's grebes are so similar they were once thought to be the same species. They intermix on both winter and summer grounds, often nesting together in colonies. Both species are bi-colored; gray or dark brown to black backs with white under sides; have red eyes; and have similar sounding calls. The differences can be subtle, but close inspection with good optics reveals the differences.
Western Grebes
The black cap on the Western grebe goes up the back of the neck to the head and extends below their red eyes. The bill is a dull yellow-green to grayish. When compared with Clark's grebes, Westerns are darker overall and usually have two syllables in their call, with a relatively harsh and high pitch "cree-creet". These calls carry well across large bodies of water.
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Clark's Grebes
The black cap of the Clark's grebe goes up the back of the neck and head and ends above the eye, leaving white feathers around their red eyes. They also have a bright yellow-orange bill. Clark's grebes appear lighter in overall color, although individual color variations and posture can be deceiving; they also typically have only one high pitch "creet" in their call.
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Threats to Grebes
Summer
On summer nesting waters, grebes are vulnerable to many anthropogenic threats. These include litter; such as this bird tangled in discarded fishing line; boat strikes, especially when back brooding; and being disturbed on nests. When grebes leave nests due to disturbance, a host of natural predators can move in to consume eggs.
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Winter
When on coastal waters in winter, grebes face different threats. These can consist of boat strikes, tangling in or consuming litter, and oil spills. This last threat, oil, is the primary reason the Grebe Project has been implemented. Grebes are one of the hardest hit species when oil spills occur on the ocean, as they are always on the water and must dive through floating oil. These birds can then lose their ability to thermoregulate due to wet feathers, or suffocate from oil entering airways.
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