Alan Grenon <agrenon at kent.wednet.edu> wrote about:

Subject: Re: Contents of the Auk - October 1996
Date: Thu, 24 Oct 1996 11:50:29 -0700

> October 1996 (Vol 113 No 4) issue of The Auk..

>Consequences of an alien shrub on the plumage coloration and ecology of
>Cedar Waxwings. Mark C Witmer. pp 735-743. Orange, instead of the =
normal
>yellow, tail bands in waxwings is the result of feeding on fruits of
>introduced Eurasian honeysuckles (Lonicera morrowii and L. tatarica), a
>food with high rhodoxanthin content, when birds are in molt. Eurasian
>honeysuckles are widely established outside of cultivation in the NE
>United States. Ecological interactions between waxwings and these
>honeysuckles underscores the unanticipated consequences that exotics =
can
>have on native organisms. The extent to which introduced honeysuckles =
may
>influence the ecology and behavior of waxwings remains to be =
determined.

You wrote: "A presentation of this material at the A. O. U. meeting this =
summer did
_not_ establish a cause-and-effect relationship between this plant and
feather color. It showed a possible correlation, leaving many variables
undescribed and the hypothesised cause untested. I'd like to know if =
the
article provides more details. I've seen some older waxwing specimens =
with
orange tail tips. . . A dietary source of feather pigment should be =
easy
to test."

Alan,

You are indeed correct: Dr Witmer writes in his abstract: "Biochemical =
studies have *implicated* a dietary cause (Hudon and Brush 1989), =
specifically the fruits of Lonicera morrowii (Brush 1990), for this =
novel color variant. I show that rectrices replaced while Cedar =
Waxwings are feeding on L. morrowii fruits develop orange tips. =
Rectrices replaced subsequent to switching the diet of molting waxwings =
from L. morrowii fruits to dog chow were yellow, showing close temporal =
correspondance between dietary input of rhodoxanthin and the coloration =
of growing feathers."

The author uses a number of 'weasel words' which are obviously intended =
to avoid a statement of cause-and-effect. If such a cause-and-effect =
was implied in my short blurb, it was an error totally of my own doing - =
in my humble attempts to share the wealth of information the learned =
ornithologists send to my mailbox quarterly, I often find it difficult =
to summarize their complex discussions into 2 or 3 short sentances. =20

Apparently, Witmer's paper is similar to what you heard at the A.O.U. =
presentation. If you would like to read the paper, you might get a copy =
from the library. Or, write to the author for a reprint of the article =
at:

Mark C. Witmer
Department of Zoology and Physiology
University of Wyoming
Laramie, Wyoming 82071
email: waxwing at uwyo.edu

However, he states that "Carotenoid pigments (i.e. xanthophylls) cause =
the yellow tail bands of Cedar Waxwings (Hudon and Brush 1989), as well =
as the red tips of their secondaries (Brush and Allen 1963). The =
coloration of the novel orange-tipped rectrices of Cedar Waxwings is =
caused by the inclusion of a red carotenoid pigment (rhodoxanthin) in =
the tail bands (Hudon and Brush 1989). Carotenoid pigments in feathers =
appear to be derived exclusively from dietary sources, either directly =
or with modification (Goodwin 1984, Hudon and Brush 1989). Dietary =
rhodoxanthin has been reported to be deposited unaltered in the =
carotenoid-containing feathers of several birds (Volker 1955, 1957, =
1958). Apparently, this pigment is not distinguished biochemically from =
the yellow xanthophylls that normally color these feathers. These =
finding suggest that the recent color variant of the Cedar Waxwing is a =
result of dietary shift to a rhodoxanthin-rich food source during the =
period of tail molt (Hudon and Brush 1989)."

It seems pretty clear to me that the link between diet and pigment =
exists for waxwings, as well as a number of other species (i.e., some =
male House Finches may have gold or yellow feathers in place of red ones =
due to a deficiency of B-carotene in the diet). The mechanism that =
causes the rhodoxanthin to replace the normal yellow xanthophylls in =
waxwings is *not* clear to me, however (But then again, it has to be a =
pretty simple expanation for me to understand a lot of physiological =
processes). I don't have an extensive-enough library to research this =
much further, but here are a few references from Witmer's "Literature =
Cited" that might pertain:

Brush, A.H. 1990. A possible source for the rhodoxanthin in some Cedar =
Waxwing tails. Journal of Field Ornithology 61:355.

Brush, A.H. and K. Allen. 1963. Astaxanthin in the Cedar Waxwing. =
Science 142:47-48.

Goodwin, T.W. 1984. The biochemistry of the carotenoids: Animals, vol 2. =
Chapman and Hall, New York.

Hill, G.E. 1990. Proximate basis of variation in carotenoid pigmentation =
in male House Finches. Auk 109:1-12.

Hudon, J., and A.H. Brush. 1989. Probable dietary basis of a color =
variant of the Cedar Waxwing. Journal of Field Ornithology 60:361-368.

Mulvihill,, R.S., K.C. Parkes, R.C. Leberman and D.S. Wood. 1992. =
Evidence supporting a dietary basis for orange-tipped rectrices in the =
Cedar Waxwing. J. Field Ornithol. 63:212-216.

Partali, V., S. Liaanen-Jensen, T. Slagsvold and J.T. Lifjeld. 1987. =
Carotenoids in food chain studies. II. The food chain of Parus spp. =
monitored by carotenoid analysis. Comparative Biochemistry and =
Physiology B Comparative Biochemistry 87:885-888.

Slagsvold, T., and J.T. Lifjeld. 1985. Variation in plumage color of the =
Great Tit Parus major in relation to habitat, season and food. Journal =
of Zoology (London) 206:321-328.

Test, F.H. 1969. Relation of wing and tail color of the woodpeckers =
Colaptes auratus and C. cafer to their food. Condor 71:206-211.

Hope this helps.

Jon. Anderson
Olympia, Washington
festuca at olywa.net