Control and Function of Carotenoid Coloration in Birds: Selected Case Studies - Carotenoids: Physical, Chemical, and Biological Functions and Properties - page 487

23 Control and Function of

Carotenoid Coloration in
Birds: Selected Case Studies

Kevin J. McGraw and Jonathan D. Blount

CONTENTS
23.1 Introduction ........................................................................................................................ 487
23.2 “You Are What You Eat”: Dietary Control of Carotenoid Coloration
in the House Finch .............................................................................................................. 488
23.3 Physiological and Genetic Control of Carotenoid Coloration in a Domestic
Songbird Model, the Zebra Finch ....................................................................................... 490
23.4 The Antioxidant Role of Carotenoids in a Colorful Raptor ............................................... 492
23.5 Developmental Predictors of Coloration in Altricial Birds: Studies of
Blue Tits and Great Tits...................................................................................................... 494
23.6 Developmental Predictors of Adult Coloration in Precocial Captive Bird Models............ 497
23.7 Carotenoid Signaling of Social Status in Widowbirds ....................................................... 499
23.8 Female Coloration and Mutual Sexual Signaling in Northern Cardinals .......................... 501
23.9 Carotenoid Coloration and Environmental Contamination: Great Tits as
Bioindicators ....................................................................................................................... 503
Acknowledgments .......................................................................................................................... 505
References ...................................................................................................................................... 505

23.1 INTRODUCTION
Many animals deposit carotenoids into external body tissues, such as skin, feathers, or other kera-
tinized structures like the beak, where they impart rich red, orange, or yellow colors (e.g., in
l amingos and guppies) or even purple and green hues when in combination with other color-
generating mechanisms (e.g., melanin pigments, structural coloration) (McGraw 2006). The caro-
tenoid basis for such colors has been known for 75 years (Volker 1938), and with that has come
widespread interest in the biological causes and consequences of carotenoid-based color displays.
Special interest has been shown in species where the sexes differ in coloration (e.g., Badyaev and
Hill 2000, Gray 1996); in most cases, males display larger areas of or more intense carotenoid
coloration and use such colors as a means of signaling their worth as a mate to females of their spe-
cies or of signaling their competitive advantages to rival males. Sexual selection is recognized as
a powerful and important evolutionary force, which has shaped variation in behavior, physiology,
and morphology, not least variation in carotenoid coloration within and among species (Andersson
1994). However, sometimes adult females or even young animals can display this form of color-
ation, and investigations into the nature and role of carotenoids in these instances have proven to
be excellent tests of the limits and generalities of theories on animal signal use (e.g., Jawor et al.
(2004) and Tschirren et al. (2005)).

487