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Battle of the blue bills

By Jeanne Raimond | Mission Trails Regional Park

Most of us delight in seeing the cute little ruddy ducks (Oxyura jamaicensis) floating on the lakes with their often cocked up “stiff” tails. Everything looks serene, but there is more to these little cuties than meets the eye.

Ruddy ducks are often just floating and dozing during the day because they have spent a considerable amount of time at night feeding, where they dive and strain mouthfuls of mud through thin plates on their large bills. They then swallow items left behind such as aquatic invertebrates, insects, mosquito larva, crustaceans, zooplankton along with small amounts of plants and seeds. They spend most of their time on the water because of limited maneuverability in the air and limited mobility on land due to the posterior placement of their legs. They swim and dive to escape predators such as hawks, owls, raccoons and weasels.

Rudy ducks at rest (Photos by Jeanne Raimond)

Although migratory throughout most of the U.S., ruddy ducks can be found year-round in the southwestern states. Locally, our numbers swell with migrants during the fall through spring.

During breeding season, the males take on bright blue bills and chestnut colored bodies. Several “ruddies” are often found on Kumeyaay Lake, and this spring I watched and photographed several males fighting each other over the females who were swimming nearby. Ruddies are known for being aggressive toward each other and toward other species, especially during the breeding season. Unlike most ducks, they form pairs only after arriving on the breeding grounds each year.

Courtship displays include males sticking their tails straight up and striking their bills against their inflated necks, creating bubbles in the water by the air being forced out of their feathers. They will then make a belch-like call. Courting males may lower their tails and run across the water while making popping sounds with their feet. I observed several males head-bobbing as they neared each other and then they went at it flailing about and stirring up quite a commotion.

Rudy ducks displaying aggression

A female ruddy chooses her suitor based on the best plumage and display. Females build nests in dense vegetation of freshwater wetlands and in brackish coastal lagoons. Most nesting locations in San Diego County are in the northwest coastal lagoons and river valleys. Nests are constructed 2 to 10 inches over cattails, bulrushes and grasses that they bend and pull under their bodies, rather than carry material to the nest. Some will use the old nests of coots. A canopy of vegetation is then woven over the nest.

Parasitic egg-laying within and between duck species may be practiced by ruddies with some “dump” nests containing up to 80 eggs. Obviously, all will not develop. An average clutch is two to 13 eggs incubated only by the female for 20 to 26 days. Egg size is 2.3–2.7 inches by 1.7-1.9 inches, which for an adult bird measuring only 15 inches in length represents proportionately one of the largest egg-to-body size in birds.

Most chicks are observed from May through most of August. The hatchlings are precocial and leave the nest within a day. They will cluster near one another demonstrating their bond as a brood as they swim with their mother. The young receive no care from the father and the mother may abandon her young after only a few days as the young are able to dive and feed themselves shortly after hatching. Unfortunately, these little ducklings are preyed upon by black-crowned night-herons and California and ring-billed gulls.

These interesting and beautiful little ducks add a bit of color to our spring and early summer, and even with duller plumage in the winter, they can be fun to watch. So get out there to the lakes and enjoy them!

—Jeanne Raimond is a trail guide at Mission Trails Regional Park.

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