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Welcome the Western Grebe

Posted: December 15th, 2017 | Columns, Featured, Mission Trails - Trail Guide | No Comments

By Audrey F. Baker

It’s that time of year! The Western Grebes (Aechmophorus occidentalis) are back in San Diego and Lake Murray is among their wintering locales. Park visitors are afforded a wonderful opportunity to view this engaging migratory species.

The birds create a striking figure — impressively sized, regal swan-like neck, elegant black-and-white scheme, pointy-crowned head bearing ruby-red eyes and a long, thin bill.

Western Grebes on Lake Murray (Photo by Wendy Esterly)

With a maximum water depth of 95 feet and a water storage capacity of 4,684.2-acre feet, Lake Murray is grebe ready. It covers 171.1 surface acres and boasts a 3.2 mile shoreline, and offers a vast water area replete with fish and vegetation. What more could a wintering Western Grebe ask for?

Skillful swimmers, the fish-eating Western Grebes dive in open waters, principally propelled by lobed feet functioning as a propeller’s hydrofoil blades. The bill is used to spear or pincer prey. They return to the surface to consume larger feeding prizes. Bottom-dwelling crustaceans and small aquatic animals including bristle worms (polychaetes) are dietary delights. Consuming feathers while preening aids in digestion.

Elaborate, dramatic and energetic, their courtship ritual is the most spectacular of North American birds, establishing Westerns as the largest vertebrates able to walk on water.

The male comes bearing gifts of aquatic vegetation. The frenzied couple rush toward each other and meet. Necks arrow straight, they rise in sync, like a double phoenix. With most of their body above water, a ballet ensues as he transfers his vegetable offering to his lady fair.

Flat again against the water surface, they quickly snap into an upright posture. The wings are thrown back and pinned against the flank of the body. With chest thrusted, head and neck positioned like an outstretched cobra, now abreast, they dash up to 66 feet over the water in about 7 seconds, leaving behind a wide and choppy wake. The display culminates with an underwater dive.

The Western Grebe is often mistaken for a nearly identical species, Clark’s Grebe. For nearly 100 years (1886 until 1985), they were considered to be one species and their subtle variances were attributed to color morph. Distinguishing them is not easy. Both measure 21.7 to 29.5 inches. (The Western slightly outweighs the Clark, making it the largest of North American’s grebes.) Binoculars aid identification refinements. Look for white surrounding Clark’s red eye and black or gray bordering the Western’s eye.

Bill coloration is the easiest indicator of species. Bright yellow or yellow orange indicates Clark. The Western Grebe’s bill is darker, showing either olive green or gray tones. Its general appearance is also darker. Remember, too, Clark’s Grebe is far rarer and has a smaller range.

Adapted to both fresh and salt water, Western Grebes historically migrate the Pacific Flyway by night from their large lake/freshwater and open wetlands breeding grounds of Southern Canada and western Great Plains states to winter along the Pacific Coast. Arriving October and November and departing by March, they traditionally populate the bight extending from Point Loma to Imperial Beach, San Diego Bay and other winter coastal “hot spots,” strictly as non-breeders.

In May 1956, a breeding site was established at Sweetwater Reservoir and, until the mid-’80s, remained the only colony. Since, the birds continued to benefit from the freshwater feeding sites and are colonizing an increasing number of local lakes and lagoons. Lake Hodges is one successful nesting site for Western Grebes. Within the year, breedings occurred for the first time in many years.

San Diego’s peak nesting is May through July. Winter broods have been observed. Amid dense and noisy colonies, usually anchored to reeds, a pile of cattail leaves and other aquatic vegetation forms the Western Grebe’s floating nest. Three to four bluish-white eggs are produced and incubate about 23 days. Born for water, the chicks climb on mom’s back shortly after hatching. Diving underwater with chicks on back is routine business. Both parents aid in feeding. The offspring advertise their appetite — the bare-skin patch atop the head turns scarlet as they beg or if separated from the parents.

If you hear a “kreed-kreek” coming from the lake, the words getting around — the Western Grebe is here!

— Audrey F. Baker is a trail guide at Mission Trails Regional Park. Check the MTRP events calendar published here or at mtrp.org or call 619-668-3281 for more information on the park’s free trail guide-led nature walks and opportunities to learn more about natural Southern California. Special walks can be arranged for any club, group, business or school by contacting Ranger Chris Axtmann at 619-668-2746 or at caxtmann@mtrp.org.

 

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