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always for the community VOL 29 NO 3
March 2022
www.valleysentinel.com
SPOTLIGHT SPOTLIGHT
“Be Reel!” Video Contest for Middle and High School Students! By Greg Bernard
ECRWSS
Postmaster: Dated Material
PRESORTED STANDARD US POSTAGE PAID DANVILLE, CA PERMIT NO. 70
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The Western Grebe’s elaborate mating rituals are a sight to see By James Hale
The Western Grebe (Aechmophorus occidentalis) is the largest grebe in North America. It weighs up to four and one half pounds, with a wingspan more than three and one half feet. Adults may reach almost three feet in length, with the long bill, head, and swan-like neck making up one half its length. It is the long neck that gives rise to the Western Grebe’s folk names of “swan grebe” and “swan-necked grebe”. Their striking red eye and straight, greenish-yellow bill are diagnostic. The whispy, raspy, haunting call of the Western Grebe is a classic sound on western waters. The long legs are located well back on the body, an adaptation for diving and fast, underwater
pursuit of their fish prey. Clark’s Grebe is a very similar looking close relative. Much phylogenetic and taxonomic research has been done to help understand the relationship between Clark’s and Western Grebes. Presently, both Western and Clark’s Grebes have two recognized subspecies. The Western Grebe exhibits classic countershading in its coloration, an example of Thayer’s Law. They are dark gray or black above, and white below. This method of camouflage is an adaptation for protection against predation from above and below. The Western Grebe is a water bird that breeds in colonies on ponds and lakes, with marsh and open water habitat, throughout
western North America, from Canada to Mexico. It winters in saltwater, primarily off the Pacific Coast, or in brackish water bays and estuaries. They are a common site in Contra Costa County in the appropriate habitat. Western Grebe fossils from the Late Pleistocene Epoch have been identified from southwestern North America. Western Grebes breed in colonies, sometime reaching into the hundreds, and generally on large inland lakes with plenty of marsh habitat for nesting. Their “Rushing Ceremony’, a spectacular, ritualized courtship and mating “dance” performed by both sexes, is dramatic and a treat to observe. The pair rear up in unison and patter across the surface of the water
to dive at the finish. It is truly one of nature’s wonders and gems. The synchronous, courtship behavior functions to strengthen the pair-bond in the monogamous Western Grebe. Once the pair-bond is established, the “Weed Ceremony” is initiated. The ceremony begins with the couple bobbing their heads up and down in water, and follows with them diving to retrieve aquatic vegetation from the bottom. Upon surfacing, the “weed” is held and presented with the bill. The ceremony continues until one of the pair flips away the “weed” to the side while resuming to a normal posture in the water. Weed Ceremony usually precedes mating and nest building behavior in Western Grebes. GREBE, continued page 7
This Month’s Special Section: page 6
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