Condition dependence of iridescent wing flash-marks in two species of dabbling ducks
Introduction
Animal coloration is thought to evolve as a compromise between two antagonistic selection pressures (Endler, 1978): sexual selection that leads signals towards maximal conspicuousness of mates and rivals (Andersson, 1994), and natural selection, through communication with prey (Rohwer and Paulson, 1987) or predators (Baker and Parker, 1979) and selecting for maximal crypsis. Under sexual selection, because females are expected to be the choosy sex, conspicuous plumage coloration is more likely to evolve in males than in females (Andersson, 1994, Hill, 2006a). Courtship and coloration have traditionally been viewed as means for the male to convey information about himself to the female (Hamilton and Zuk, 1982, Andersson, 1994). This may include information on species identity and individual quality. Among birds, ducks (family Anatidae) display some of the most complex behaviours and brightest plumage (Lorenz, 1978), involving both pigments and feather microstructure.
Cues in mate choice such as courtship activity (Bossema and Kruijt, 1982, Holmberg et al., 1989), hormonal status (Sorenson et al., 1997), body condition (Holmberg et al., 1989) and bill or plumage coloration (Holmberg et al., 1989, Omland, 1996a, Omland, 1996b, Peters et al., 2004), have been investigated in ducks. However, as pointed out by Davis (2002), little attention has been paid to female phenotype. While it is well established that females prefer to pair and mate with brighter and/or more colorful males (review by Hill, 2006a), there is also growing evidence that males too make pairing and mating choices, leading to conspicuous female signals at least in some species (review in Amundsen and Pärn, 2006). Even in such highly sexually dichromatic species, both males and females possess wing flash-marks.
The information content of these wing flash-marks is unclear (Omland, 1996a, Omland, 1996b, Sorenson and Derrickson, 1994). The wing flash-marks in dabbling ducks come from iridescent feathers that diffract ambient light and compose a structural color trait (Hill, 2006b). Nutritional condition of an individual during molt might be reflected in the expression of structural coloration (review in Hill, 2006b). Previous studies on mallard and other closely related dabbling duck species have suggested that breeding ability was related with body condition (e.g. Heitmeyer, 1995, Blums et al., 2005). Moreover, nutrient reserves on the wintering grounds affect survival as well as pairing success, hence future reproductive success (e.g. Pawlina et al., 1993, Guillemain et al., 2008). Generally, ducks pair in fall and winter (Hepp and Hair, 1983), which is also when they exhibit courtship behaviours. In ducks, reflectance spectrometry has been used to study bill color in the mallard (Peters et al., 2004) and wing flash-marks in the common eider, Somateria mollissima (Hansen et al., 2006, Hansen et al., 2008), while other male ornaments have only been investigated using human vision (Holmberg et al., 1989, Omland, 1996a, Omland, 1996b). By using recent spectrometry techniques, our aims are twofold:
- (1)
With mallards fed ad libitum held in semi-captivity, we investigated reflectance intensity delivered by the flash-marks at the beginning of the pairing period and soon enough after molting to avoid feather degradation after growth. We investigated the possibility of condition dependence of the wing flash-mark coloration and tested the relationships between body size (or condition, two individual phenotypic measures known to modulate breeding performance in Anatidae) and feather reflectance. We expect a positive relationship between body condition and flash-mark reflectance for both sexes.
- (2)
Compare the signal obtained when individuals came from natural habitats (killed by hunters in autumn and winter, i.e. during the pairing period of these species; Hepp and Hair, 1983). Same predictions on sex and condition (or size) listed in point 1 are expected for wild individuals. We also expect wild individuals to display lower quality plumage than semi-captive individuals due to a more constraining environment in nature (i.e. less food availability, Hill, 2006b).
Finally, we hypothesize that, overall structural plumage gradually fades due to the abrasion mediated by keratinolytic bacteria (Burtt and Ichida, 1999, Shawkey et al., 2007) or to natural abrasion, and therefore expect a decrease of plumage coloration over time.
All our predictions are tested according to two different measures of the feather reflectance spectra: color and brightness contrasts (see Section 2).
Section snippets
Feather collection and body measurements
We collected one feather from the wing color flash-mark (also termed “speculum”, i.e. the distal side of secondary remiges) of each individual killed by hunters or reared in our laboratory.
In the laboratory, feather collection took place in September for semi-captive mallards (N = 19 female and 23 male mallards) fed ad libitum with a mix of wheat and corn grains. Adult ducks descended from individuals caught in the wild.
We measured body mass, flattened wing length, tail length (length of the
Results
For both species, reflectance spectra of dabbling ducks wing flash-marks showed both a peak in the UV and a peak in the visible wavelengths (Fig. 1). In mallards, the UV peak occurred on average at 346.9 nm ± 25.5 SD for wild (N = 339) and 342.3 nm ± 18.4 SD for captive mallards (N = 42). The blue color peak occurred on average at 463.6 nm ± 9.06 SD for wild individuals and at 470.0 nm ± 8.4 SD for captive ones. In teal (N = 1167), the UV peak occurred on average at 340.8 nm ± 41.8 SD and the green at 547.6 nm ± 48.2
Discussion
Our results revealed that body size (and condition to a lesser extent) and structural signals were related in ducks. This was especially true for semi-captive birds, measured soon after molting. The positive relationships were significant in females but not in males, a result consistent with what was found for wild teal on wing length. Wild birds were less bright and colored than semi-captive birds fed ad libitum. In natura, we first found an age effect indicating that adults were more colored
Conclusion
This study suggests that brightness and color contrasts are involved in different signaling functions. Sexual differences in speculum coloration are related to color contrast while the brightness contrast is more influenced by time. Individuals able to produce more colorful structural feathers, well discriminated at short distance, would be less conspicuous to predators using brightness contrast from a longer range. Mediated by both natural and sexual selection, colorful individuals should be
Acknowledgements
We sincerely thank Franck Latraube and Francois Bourguemestre for their help in collecting feathers in the field. We are grateful to the staff members of the Fédération Départementale des Chasseurs de l’Indre (FDC36), the Association des Chasseurs de Gibiers d’Eau de l’Indre and the Réserve Naturelle de Chérine (especially Jacques Trotignon) for their continuous support. We strongly acknowledge the hunters who provided teal wings to ONCFS, and the valuable help of Vincent Schricke and David
References (60)
Why are females birds ornamented?
Trends Ecol. Evol.
(2000)Female choice and benefits of mate guarding by male mallards
Anim. Behav.
(2002)- et al.
Males prefer ornamented females: a field experiment of male choice in the rock sparrow
Anim. Behav.
(2005) - et al.
Female mate preferences and male attributes in mallard ducks Anas platyrhynchos
Anim. Behav.
(1989) - et al.
Hormonal dynamics during mate choice in the northern pintail: a test of the “challenge” hypothesis
Anim. Behav.
(1997) - et al.
An experimental test of the dose-dependent effect of carotenoids and immune activation on sexual signals and antioxidant activity
Am. Nat.
(2004) - et al.
On the function of female ornaments: male bluethroats prefer colourful females
Proc. Roy. Soc. Lond. B
(1997) - et al.
Female coloration: review of functional and non-functional hypotheses
Sexual Selection
(1994)- et al.
The evolution of bird coloration
Philos. Trans. Roy. Soc. Lond.
(1979)
Identification Guide to European Non-passerines
Correlates of lifetime reproductive success in three species of European ducks
Oecologia
Individual quality, survival variation and patterns of phenotypic selection on body condition and timing of nesting in birds
Oecologia
Male activity and female mate acceptance in the mallard (Anas platyrhynchos)
Behaviour
Occurrence of feather-degrading bacilli in the plumage of birds
AUK
Handbook of the birds of Europe the middle east and North Africa. The birds of the Western Palearctic
Repeatability of some animal-related variables in dairy cows and buffaloes
Anim. Welf.
Female coloration indicates female reproductive capacity in blue tits
J. Evol. Biol.
A predator's view of animal colour patterns
Evol. Biol.
European flyway permeability and abmigration in teal Anas crecca, an analysis based on ringing recoveries
IBIS
The income-capital breeding dichotomy revisited: late winter body condition is related to breeding success in an income breeder
IBIS
Optical Signals, Animal Communication and Light
Heritable true fitness and bright birds: a role for parasites?
Science
A label of health: a previous immune challenge is reflected in the expression of a female plumage trait
Biol. Lett.
White plumage reflects individual quality in female eiders
Anim. Behav.
Differences in color vision make passerines less conspicuous in the eyes of their predators
Proc. Natl. Acad. Sci. U.S.A.
Influences of age, body condition, and structural size on mate selection by dabbling ducks
Can. J. Zool.
Reproductive behavior and pairing chronology in winter dabbling ducks
Wilson Bull.
Mate choice, mate quality and carotenoid-based plumage colouration
Cited by (19)
Information out of the blue: phenotypic correlates of abdominal color patches in Sceloporus lizards
2021, ZoologyCitation Excerpt :Many congeneric species share similar coloration patterns (Gumm and Mendelson, 2011; Matysioková et al., 2017; Pizzigalli et al., 2020), but the vast majority of studies that have examined phenotypic correlates of color ornaments have focused only on single species (Kelly et al., 2012; Ibáñez et al., 2014; Merkling et al., 2018). Therefore, the degree of conservatism in the signals transmitted through coloration is still largely unknown, because only a handful of studies have compared the information transmitted through particular color ornaments between species from the same genus (e.g. Moretz and Morris, 2006; Legagneux et al., 2010) or family (e.g. Arenas et al., 2015; Mészáros et al., 2019). If the physiological mechanisms that underlie production and deposition of pigments are shared across closely related species, then the signals transmitted through color ornaments are likely similar among such related species.
Body mass and immune function, but not bill coloration, predict dominance in female mallards
2016, Behavioural ProcessesCitation Excerpt :This situation is exactly the opposite of that described by Murphy et al. (2014), where bill color appears to serve as a signal only for females—male bill coloration is used neither to mediate competition nor in mate choice by females (Murphy et al., 2014). Second, recent work has linked chromatic attributes of female (but not male) duck plumage to indexes of condition (Legagneux et al., 2010), suggesting that the most informative signals of quality among female ducks may be plumage-, rather than bill-based (but see Lehikoinen et al., 2010). Third, the multiple competitor environment that we experimentally created may have limited the efficacy and utility of all signals, thereby increasing reliance on physical aggression and body size.
Iridescent plumage in a juvenile dromaeosaurid theropod dinosaur
2023, Acta Palaeontologica PolonicaSole coloration as an unusual aposematic signal in a Neotropical toad
2019, Scientific ReportsReduced sexual dichromatism, mutual ornamentation, and individual quality in the monogamous Zenaida dove Zenaida aurita
2017, Journal of Avian Biology