diet?

red plumage is often dependent upon diet in birds.

regards,

Deborah Wisti-Peterson, PhD Candidate nyneve at u.washington.edu
Department of Zoology, University of Washington, Seattle, Wash, USA
Visit me on the web: http://students.washington.edu/~nyneve/
Love the creator? Then protect the creation.

On Mon, 20 May 2002, Maureen Ellis wrote:

> Mike and Everybody,
> The primaries and rectricies on all the birds I saw in this group were
> rich dark black! So, these were all fully mature males. Hum? What could
> be limiting the intensity and the extent-of-coverage of red on the heads
> of these male tanagers? Some dietary deficiency or maybe some metabolic
> toxin that they picked up on their wintering grounds? I know that the
> males do have more yellowish on the head in winter, but it is now mid-late
> May. Would you expect the majority of the males to be in full breeding
> colors by this time? None of the males in this group were in full
> alternative plumage yet.
> Tiz a puzzlement, me2
> ****************************************
> Maureen Ellis, PhD, Research Scientist
> Toxicology Group at Roos 1, 284A
> Lab/Office phone: 206-685-1938
> Dept of Environmental Health, Mailstop 354695
> School of Public Health and Community Medicine
> University of Washington, Seattle, WA 98195
>
> E-Mail: me2 at u.washington.edu
> ****************************************
> "Why are we now traveling into space? Why, indeed, did we trouble to look
> past the next mountain? Our prime obligation to ourselves is to make the
> unknown known. We are on a journey to keep an appointment with whatever
> we are."_____Gene Roddenberry
>
> On Mon, 20 May 2002, M. Donahue wrote:
>
> > Maureen and Tweeters,
> >
> > I studied a large series of western tanager specimens, in order to
> > characterize and describe their molt cycle. (The results of this project
> > will be published in The Auk later this year, in a paper coauthored with Luke
> > Butler and Sievert Rohwer.) I wasn't specifically collecting data on the
> > extent of red on the head, but anecdotally, the one year old males did not
> > have less red on the head than older males. I was surprised at this finding,
> > as it was not what I would have predicted.
> >
> > The best way to age male western tanagers in the spring is by the color of
> > their flight feathers (the primaries and rectrices). One year old males
> > still have the flight feathers that they grew as juveniles, which by this
> > time of year are a faded olive green (which appears brownish). The older
> > males, those at least two years old, have black primaries and rectrices.
> > This difference is actually fairly easy to observe if you get a half way
> > decent look.
> >
> > >From the distribution of age classes in the spring--dates and
> > localities--it appears that the one year old males do indeed migrate later
> > in the spring than the older males.
> >
> > Mike Donahue
> > Seattle
> >
> >
> >
> >
> >
>
>