[CT Birds] An interesting study
dennisvz at optonline.net
Fri Jun 12 12:56:15 EDT 2009
I ran across this article which I think others may find interesting
It is about how visual characteristics of males can provide
information about the health of the bird to help females choose the
Carotenoids have been identified as the main pigments involved in the
expression of Yellow to Red Sexual Signals in fish and birds.
Carotenoids can be displayed in plumage or soft parts, such as bill,
feet, eyes etc. They can not be synthesized but must be ingested.
Also, they are used in the immune response. If a bird displays a lot
of color, it was skilled in acquiring carotenoids and is healthy. If
a bird displays little color, then it is less skilled in acquiring
carotenoids and/or is fighting a disease
This study used Zebra Finch Bill color as a measure of attractiveness
(Orange vs. Red). First they gave two groups of birds carotenoid
laced water to produce maximum carotenoid concentration in the blood
and very colorful bills. Then, one group was given an infection of E.
coli in order to activate the immune system.
Immune activation diverted carotenoids from blood plasma and this in
turn affect the expression of the bill color making birds less
attractive. This study support the idea that carotenoids have
important physiological properties that ensure the honesty of
carotenoid-based sexual traits.
What is meant by “ensure the honesty of carotenoid-based sexual
traits.” is that females can use bill color as a measure of male
fitness that can not be “faked”.
Witht respect to Connecticut birds , the most obvious birds where
this is relevant are Tanagers and Orioles. Also, I would guess Red-
winged Blackbirds and American Redstarts. With regard to soft parts,
I would guess American Oystercatchers would be a prime candidate,
withe their orange bills and legs.
Right now there are plenty of Oystercatchers at Mlford Pt. and Sandy
Pt. West Haven. chasing each other around. It might be interesting to
watch them and see if there are differences in color and if the
dominant birds have brighter bills
An Experimental Test of the Dose-Dependent Effect of Carotenoids and
Immune Activation on Sexual Signals and Antioxidant Activity
American Naturalist 164 (651-659) 2004
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