Monday, August 24, 2015

The Pied-billed Grebe is a Feather Eater!

Pied-billed Grebe by Rick Heil

I've seen a Pied-billed Grebe at the salt pannes a few times on the Refuge recently.  I introduced the bird to a new birder on Thursday evening.  Grebes do fascinate me!


Gill's "Ornithology" mentions “…grebes have high wing loading.  To take off, they must run over the water, flapping their wings to gain enough lift for flight."  Lots of energy is expended to take flight; an apprehensive grebe will dive, sink or swim to escape predators. Once while foraging in vegetation a grebe sunk and revealed only its bill above water; I thought of a submarine, a ship that can operate both under and on top of the water, 
and that bill was the periscope. 


Grebes have tiny, saw-like teeth on the edge of their bill which aid them in feeding on aquatic invertebrates, vegetation, insects, fish and frogs.  This chicken-like bird is usually absent from our landscape from the middle of November to the middle March.  In late fall, they migrate south where it’s certain to be more hospitable.  Veit and Petersen’s “Birds of Massachusetts” reports Pied-billed Grebes are first “irregular in winter” and secondly, “During mild seasons, when ponds and bays remain unfrozen, Pied-billed Grebes are capable of surviving the entire winter in Massachusetts.  Most birds are found on Cape Cod and the island, but there are midwinter reports from inland localities…”

Grebes compress air out of their feathers and air sacs by contracting the firm and toned abdominal muscles which regulate their buoyancy and shape.  Their plumage is satiny and well preened.  They are similar to coots and phalaropes in that their toes are lobed and each toe has lobes extending out on the sides providing extra surface area for paddling. The grebe's tarsi are laterally compressed. 
Highly designed for water with legs set far back on the body like "divers", making them efficient waterbirds.  They’re gawky on the solid part of the earth's surface and come to land to nest. They bathe and preen in the sun while I peered through my scope.  I watched as they used their billsto obtain oil from the oil gland.  Grebes are often described as tail-less, and Proctor & Lynch’s “Manual of Ornithology” refers to the tail of the grebe as vestigial. 
I read in Alexander Wetmore's “Water, Prey and Game Birds of North America” that grebes eat their own feathers. Wetmore states "Strangely, grebes eat their own feathers, retaining them in their stomachs in a tight ball until they disintegrate enough to pass through.  The clumps may hold back such objects as fish bones until they are soft enough to digest."  Wetmore, a past president of the American Ornithologist's Union, lists the Pied-billed Grebe’s monikers as “hell-diver, water witch and dabchick”.

“The Sibley Guide to Bird Life and Behavior” notes “The feathers may protect the stomach from puncture by indigestible parts of the grebe’s prey and prevent hard items from entering the intestines.  They also provide the base material of regurgitated pellets that contain undigested material such as fish bones.”

Good birding,
Sue

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