Thursday, March 22, 2018

The Curious Case of the Pied-Billed Grebe

Grebes of the family Podicipdedidae are a group of aquatic diving birds, representatives of which are found of every continent except Antarctica.  Of these 20 species, the most widespread in North America is the Pied-billed Grebe (Podilymbus podiceps). 

Often found next to the loons (family Gaviidae) in field guides, these two groups of birds are both poorly adapted to life on land, with feet placed very far back on their bodies.  Though it makes them appear ridiculous and nearly helpless ashore, this arrangement serves aquatic birds well as they swim underwater, using their feet for propulsion. 

Grebes often dive below the surface with scarcely a ripple, and have a maddening habit (for the birder with a camera or scope) of surfacing many meters away from the point where it disappeared.  Grebes (as well as loons) are also known for their submarine-like habit of sinking stealthily beneath the surface until only its periscope-like head remains above the water. 

The life of the Pied-billed Grebe is tied to water - more specifically to the freshwater marsh - and feeding, breeding and nesting all take place in the water.  (Nests are usually on little islands built up in shallow water, or on floating mats of plant matter anchored to standing reeds or other vegetation.)  Grebes feed on aquatic critters, from insects and snails to frogs and fish, generally foraging underwater as they swim. 

Like other grebes, Pied-billed Grebes eat feathers and also feed them to their young.  Text from a Stanford paper  (my apologies to my husband and father-in-law, die-hard Cal Berkeley fans) notes that up to 50% of a Pied-billed Grebe's stomach may be filled with feathers.  One reason grebes may have developed this curious habit is to compensate for a gizzard that lacks the power to sufficiently grind up fish bones.  A padded ball of feathers in the stomach of a grebe protects the stomach from the sharp bones and allows them time to be dissolved by stomach acids, or formed into a pellet to be expelled before matter is passed through the delicate intestines. 

Pied-billed Grebes are very rarely seen in flight, and generally do so only during migration, which takes place at night.  Not surprisingly, grebes require water for take-off, as they "run" across the water in order to become airborne.   

During the spring breeding season, Pied-billed Grebes become more secretive, often hiding in marsh vegetation.  At times, the only indication of their presence are their unnervingly loud cries, bizarre sounds described as whinnying, whooping, chattering or gobbling, echoing across the wetlands; to me, it sounds a little like the reeds are filled with maniacal laughter.  A curious little bird indeed.

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