- The main problem with the PHOTO of this bird is that it is too yellow to make ANY determination about color:Message 1 of 2 , Nov 3, 2005View SourceThe main problem with the PHOTO of this bird is that it is too yellow
to make ANY determination about color:
As far as bill length of a photographed Bell's Vireos (BeVi, or of the
Western LBVI), one can see variation based on age of individual, and a
bird in head molt may show a longer bill than one with fully developed
(new or old) throat and cheek feathers. In addition, length of bills
within a population may vary as much as 5% (based on measurements I
made of 30+ females and 30+ males in 1980), and may also vary between
the sexes by a similar amount (all hard body parts usually measured -
tarsus, bill tip-to-gape, culmen - have a range of length that may vary
that much, if not slightly more).
Finally, bill may seem longer or shorter than something simply due to
the angle at which the photo was made.
I would be cautious about assigning a particular bird to nominate or
western race on either bill length or color as depicted in a photo,
UNTIL the issue of color in the image is sorted out.
It's great enough that it's a Bell's Vireo in Central California at
that time of year!
Santa Barbara CA
- ... Vireos (BeVi, or of the ... individual, and a ... with fully developed ... If the bird is in migration, wont it have either finished its body molt, or notMessage 2 of 2 , Nov 3, 2005View Source
> As far as bill length of a photographed Bell'sVireos (BeVi, or of the
> Western LBVI), one can see variation based on age ofindividual, and a
> bird in head molt may show a longer bill than onewith fully developed
> (new or old) throat and cheek feathers.If the bird is in migration, wont it have either
finished its body molt, or not started it yet?
According to Pyle (1997), the "pre-basic" molt occurs
on the summering ground, so this bird ought to have
already completed its first molt (out of juvenile
plumage) and be in formative (the old first-basic)
plumage by now. So, it would seem that head molt
would not affect the apparent length of this bird's
bill. Just a thought,
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