Subject: Re: Pied-billed Grebe behavior
Date: Jun 8 08:25:18 1998
From: "Martin J. Muller" - martinmuller at email.msn.com


Jim, fellow tweetsters,

I'll tackle the pied-billed grebe behavior part of Jim's question.
In order of seriousness of the threat, pied-billed (and several other)
grebes will first assume a forward threat posture. In the case of the
pied-bill that is the posture with retracted, kinked neck, black throat area
(in breeding plumage) distended and chin almost or actually touching the
water, the bill (weapon) pointing at the opponent.

Most water fowl recognize and take serious this threat from a pied-bill, for
it may lead to dashes and chases along the surface, then by dives during
which the birds races at the opponent just below the surface, creating
ripples betraying the grebe's path. This still gives the target bird a way
to see where the grebe is.

The ultimate threat is when the grebe dives and does not show its path of
attack. Grebes do stab or pinch with their bills from under water. I've seen
birds under attack jump clear off the water while being held onto by a grebe
(grebe usually grabbing a leg or belly or tail feathers). This mode of
attack is most often directed at other grebes intruding in the bird's
territory but it may also be directed at most other water fowl. I have not
seen it directed at either double-crested cormorant or common merganser, two
species that are capable of outmaneuvering pied-bills under water. But from
American coot to Canada goose, everybody else heeds the warning of an
aggressive pied-bill.

In the case of western grebes, they may actually stab, wound or even kill
other birds with their pointed bills. However the pied-bill's bill is not a
stabbing instrument, more of a crushing instrument (crustaceans are an
important part of their diet). I once rescued a pied-bill from fishing-line
entanglement. While I had the bird in the hand I thought I'd take some
pictures. However, the little fella showed me how serious a weapon the bill
is by nabbing my thumb and drawing blood. A convincing argument to dispense
with the photo-op and set him free pronto...

Hope this answers your question.

Sincerely,

Martin Muller, Seattle
MartinMuller at email.msn.com