Hi Tweets,

Wayne Weber writes:

> The song described second-hand by Michael Price on June 11 as "a
>series of mockingbird-like repeated notes"-- if the singer was indeed
>correctly identified as a Black-headed Grosbeak--

Wayne's unsubtle denigration of their skills aside, the observers were not
mistaken in their identification of a species with which they're both
familiar: to reiterate: they watched the grosbeak uttering a
chat/mockingbird-like song for several minmutes before singing elements of
the more conventional BHGR song.

>is a highly aberrant
>one for that species.

The aberrancy is more of an assumption than hard fact: both species sing
from cover much of the time, and grosbeaks, like many of the finches,
clearly has a capability for mimicry which may be mistaken for other species
even by ornithologists, however skilled, who do not get a visual
confirmation to their auditory ID. This may be a far more common occurrence
than we think, and in fact such mimicry might be a standard response to a
perceived territorial threat from an alien species in the same habitat.

Once, years ago, I was at the Iona settling ponds at a time when there were
several pairs of nesting Killdeers Charadrius vociferus and a single vagrant
Willet Catoptrophorus semipalmatus. Unusually (normally this Vancouver
vagrant species stays silent), the Willet began uttering its
'prrrilll-illl-illit!' call. I nearly fell over when the Killdeers all began
loudly *mimicking* the Willet's call. For the next three or four minutes,
the settling ponds sounded like a bedlam of Willets. Then, when the calls
died away, the Willet started calling again, and again all the Killdeers
responded by echoing the call. I stress that it was a *perfect* mimicry.
This happened five or six times, then everyone seemed to lose interest.

Nobody I've talked to has ever had a similar experience, and when I told
Wayne about this in hope of getting some kind of explanation, he just
laughed in my face and flatly refused to believe it had happened at all (and
presumably still doesn't), showing that aberrancy may be as much in the mind
of the beholder as in nature. Incidentally, years later, I *still* haven't
the faintest idea why (nesting) Killdeers would mimic Willets. Not a clue.
It may be something to do with Killdeer territoriality or call-similarity or
Willet predation on Killdeer chicks or the moon being in Capricorn. I really
don't know. But I do know that outright skepticism is usually less fruitful
than speculation about what mechanism might account for unusual behavior in
usual species. Such examples demonstrate that even common species can often
confound our certainties and mock our hubris.

>The grosbeak's normal song, a series of rapid,
>rich warbles, is easily confused by inexperienced (or
>hearing-challenged) birders with that of an American Robin, a Hepatic
>Tanager, or perhaps even with a Red-eyed Vireo. However, it bears no
>resemblance whatsoever to the normal song of a Yellow-breasted Chat.

Stipulated.

> Among thousands of Black-headed Grosbeaks that I have heard
>singing over several decades, I have never heard one sing in the
>manner described by Michael. (I acknowledge that Michael was not the
>actual observer, and the description of the song may have lost a
>little in the translation.)

Well, ignoring Wayne's second, more subtle slur on the observational
abilities of the birders who related this incident to me, or on my ability
to mediate the matter--I can't quite make out which-- I agree: neither have
I. But BHGR songs aren't quite as standardised as Wayne's remarks imply:
there is suffcient difference in intonation, cadence and quality to make a
blanket statement unwise. Some of these differences may be age-related, or
depend on nearness of fledging of the young or whether a bird is a
sexually-prospecting or territory-less male or is incorporating phrases of
another species' song or some other factor. Individual birds in migration or
displaced by habitat destruction may sound different to the standard song.
Heck, even individuals in adjacent territories sound slightly different to
each other. Individuals at the extremes of BHGR songs are not only going to
sound different to each other but are also gojng to sound different from the
norm. All this is to say that one should expect a wider range of variation
in song-phrasing and -quality even in Black-headed Grosbeaks than one would
think at first encounter. And be prepared to be surprised from time to time
by more odd flukes than you'd expect.

Michael Price
Vancouver BC Canada
mprice at mindlink.net