A Mimic I've Been Waiting For...

Jim Felley (IRMSS668@SIVM.SI.EDU)
Mon, 11 Jan 99 16:21:23 EST 

Greg,
   I have heard putative American Crows give the Fish Crow call.
Note that the juvenile begging call sounds a lot like a Fish Crow,
though it is not steretypically doubled, like the 'unh-unh' call
of the Fish Crow.
   I had a lot of experience listening to Fish Crows in Lake Charles,
LA, where they breed and form large roosts just as American Crows
do (See addendum below).  My impression after listening to Fish
Crows for 7 years is that they ALMOST NEVER have a raspy note in their
call ('cah' rather than 'car').  The only times I heard raspy notes
enter their vocabulary was when a flock was mobbing a predator.
   So I have devised the following scheme for 'identifying'
an unknown crow in the DC area:
   1.  While just schmoozing around, does the bird utter raspy notes?
       It's an American Crow.
   2.  Does it intermix raspy and non-raspy (even 'unh-unh' double
       notes)?  It's an American Crow
   3.  Does it only utter the non-raspy calls?  It could be a Fish
       Crow or an juvenile, begging American Crow.

   For (3), I further ask:  Is it with a group of raspy-calling
   crows? Most likely it's a young American Crow with its family.
   Is it with a group of similarly non-raspy callers?  Most likely
   it's a Fish Crow.
   Is it calling during the Fall or Winter, when those pesky juveniles
   should have stopped begging, already!?  Most likely a Fish Crow.

   Notice that in this scheme, my ID's of American Crows are generally
   non-qualified, whereas all the criteria for Fish Crows are qualified
   with 'most likely'.

   When confronted by an 'unambiguous' Fish Crow, (not the qualifying
quotes again), I have strained to detect some morphological criterion
for separation:  Fish Crow smaller, shinier, thinner-billed, longer-
legged, etc.  In the DC area, all have been defeated by one 'car'
given by the bird as it flew off.
   Now I hear a rumor that there may be hybridization between the two
in this area.  If people wishing an unambiguous Fish Crow, Lake Charles
may be the best bet.

Addendum:  Everyone likes going to far-flung places to see huge flocks
of birds: Flamingos in East Africa, Eastern Shore for Snow Goose, etc.
How come people aren't coming to White Flint Mall in Rockville to see
the 10's of thousands of flocking American and (I think) Fish Crows
that assemble in the area every night?  It's on a Metro stop, for
heaven's sake!

                            Jim

                            Jim Felley
                            Smithsonian Institution
                            irmss668@sivm.si.edu