Carotenoid-based ornaments are often considered to be honest indicators of individual quality assessed by potential mates. However, males can use a variety of strategies that minimize the amount of costly carotenoids used while retaining the effectiveness of color signaling. Birds could do this by altering pigment intake, metabolism, or its presentation to a potential signal receiver. Here, we propose a new mechanism of lowering the costs of carotenoid displays in birds: differential allocation of pigments within single feathers.
We studied the coloration of the yellow terminal tail bands of rectrices of male Bohemian waxwings. Using reflectance spectrometry, we show that the two central rectrices are most intensively colored compared to other rectrices. More detailed analyses reveal that these differences result from feather-specific patterns of rectrices coloration. The outer feather vanes of the outermost rectrices are more intensively colored compared to the inner vanes. However, the central rectrices have equally colored vanes that are, on average, more intensively pigmented than the outermost rectrices.
When the waxwing tail is folded, the outermost rectrices are covered by other feathers, except for the narrow, outer vane. Central rectrices, however, form the outermost layers which are not obscured by other tail feathers. Thus, the feather vanes that are the most visible to potential viewers are also the most pigmented. These results support the occurrence of a previously overlooked mechanism to reduce the costs of carotenoid-based ornaments: precise pigment distribution to maximize efficiency of signals within single feathers.
Males of many bird species use bright carotenoid-based plumage coloration to attract females. These traits are physiologically expensive such that only individuals in prime condition can develop the most vivid colors.
We showed that this goal could be achieved by differential deposition of pigments into the most conspicuous feather regions. Bohemian waxwing males have yellow tips on their rectrices of which the outer vanes are more brightly colored compared to the inner vanes. These inner feather vanes are usually covered by other feathers and are, thus, less visible to conspecifics. The only exception is the pair of central rectrices that are fully exposed, and both feather vanes are equally colored.
In this species, males minimize the use of costly carotenoid pigments while maintaining elaborate ornamentation of plumage regions that are most visible to potential mates. In many animal species, the evolution of showy secondary sexual characters in males is thought to be driven mainly by female choice Andersson ; but see examples of intraspecific signal evolution of ornaments, e.
These characters include integument coloration e. The central assumption of honest advertisement models of sexual selection is that ornaments are costly to produce Zahavi , However, tactics used by males to reduce ornament production costs may weaken the linkage between ornament quality and condition Hill ; Badyaev This process should induce sexual conflict because females should seek cues that accurately reflect male quality Hill Carotenoid plumage is an example of costly ornamentation, and males could benefit by expressing it at reduced costs.
Carotenoids are acquired solely through diet, and animals experience trade-offs between allocating pigments into the integument coloration versus toward other important physiological functions, like cellular respiration Hill , Hill and Badyaev reviewed several strategies used by males to reduce the cost of carotenoid-based ornaments.
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These strategies can be divided into two classes. The first class is associated with carotenoid acquisition and metabolism. For example, males may adjust their diet to maximize carotenoid intake during the time of ornamental plumage growth McPherson that could be accomplished by selectively choosing carotenoid-rich food or a food containing carotenoids that can be directly deposited into ornaments Badyaev Alternatively, birds can selectively metabolize only the carotenoids that are used for pigmentation, a strategy observed in flamingos Phoenicopterus spp.
In the second strategy class, males alter the expression of carotenoid ornaments by maximizing the display of pigments Hill For example, confining a pigmented plumage area to a small patch can lead to an increase in color intensity or feather structure can be modified such that the coloration is displayed in the most efficient manner Hill Although examples of such mechanisms were described decades ago Hill and papers cited therein , this process has yet to be quantitatively described.
We propose a new mechanism for lowering the costs of carotenoid-based plumage displays in birds: males produce more elaborate coloration on the feathers and feather parts that should be the most visible to the signal receivers. We suggest that reduced production costs could be obtained by uneven incorporation of carotenoids over ornaments.
Our model species is the Bohemian waxwing Bombycilla garrulus , a species with multiple carotenoid-based ornaments: a yellow terminal tail band; yellow, oval spots on the tips of the primary feathers; and red, waxy appendages on the secondary feathers Svensson Although these carotenoid ornaments occur in both sexes, males display larger appendages and yellow patches that are more intensively colored Svensson A clear dichromatism in carotenoid ornaments suggests that these traits could evolve as a result of female mate choice in Bohemian waxwings.
Female preferences for red appendages have been demonstrated in the closely related species, cedar waxwing Bombycilla cedrorum , Mountjoy and Robertson Here, we focused on the yellow tail band of males that is pigmented with canary xanthophylls A and B McGraw To minimize observer bias, blinded methods were used during material collection and subsequent measurements and analyses. Sex was determined by morphological features Svensson , and visual assessment of reproductive organs during dissection and male age was determined by feather morphology Svensson In this study, we used 35 yearling males.
Thus, the plumage ornaments that we studied were grown while the male was a juvenile nestling or fledgling. However, yearling Bohemian waxwings may breed and perform courtship displays similar to adults Cramp ; it is therefore reasonable to assume that their colorful feathers may play a role in sexual selection. Before dissection, all 12 rectrices were plucked and stored in plastic bags in the dark until further measurements. We measured reflectance of all 12 rectrices. We took six readings from the dorsal side of yellow tip in each rectrix, including three readings per inner and outer vane.
We processed all the spectral data using RCLR v0.
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We transformed chroma values into positive values that are intuitively more appropriate; the higher values express a higher carotenoid chroma. In the analyses of between-feather color variation, we used a carotenoid chroma averaged for the entire dorsal side of the vane.
In remaining analyses, we used a carotenoid chroma averaged separately for the inner and outer vane. We used ANOVA for repeated measurements to test for differences in the average carotenoid chroma between yellow tips of all rectrices. In this case, 12 repeated measurements were compared. We applied the same method to test for differences in the coloration between the outer and inner feather vanes in right outermost R1 and right central R6 rectrices. In total, four repeated measurements were compared.
In both analyses, we used the Tukey honest significant difference HSD test for post hoc comparisons. Symbols on the x-axis refer to rectrices on the left L and right R sides of the tail. Rectrices 1 and 6 are the outermost and innermost tail feathers, respectively. Results of Tukey HSD tests comparing values of carotenoid chroma of the yellow tips of the rectrices of yearling male Bohemian waxwings.
For explanations of symbols, see Fig. Values in each cell are p values for a given pair of comparisons. Carotenoid chroma of the outer and inner vanes of the yellow R1 and R6 rectrices of yearling male Bohemian waxwings. Filled square outer vane; empty square inner vane.
Mean reflectance spectra of the yellow tips of the rectrices of male Bohemian waxwing. The gray and black lines refer to R1 and R6 rectrix, respectively. Solid and dashed lines refer to outer and inner feather vanes, respectively. Our results demonstrate that, within the same pigment ornament, coloration is significantly differentiated between feather types and feather vanes.
Several lines of evidences suggest that this differentiation could evolve as a consequence of an evolutionary strategy to lower the costs of male ornament production while simultaneously maintaining its efficiency as a visual signal.
Our study provides the first evidence of this mechanism. A photograph showing the positions of the rectrices on the dorsal side of the tails of Bohemian waxwings the two central feathers L6 and R6 are labeled. Because our study is correlative, we cannot rule out other, non-adaptive, explanations for the color pattern of waxwing rectrices.
Research on several other species, including cedar waxwings, indicates that yellow, carotenoid-based coloration is a product of both pigment deposition and feather microstructure Shawkey and Hill It is therefore possible that differences in Bohemian waxwing tail coloration could be, at least partially, a by-product of keratin organization in barbs. However, recent studies have revealed that carotenoid-based coloration is more influenced by a variation in carotenoid content than feather microstructure Shawkey et al.
Thus, a variation in feather structure probably does not explain differences in the coloration between rectrices and their vanes in Bohemian waxwing males. Another possible explanation of between-feather variation in carotenoid chroma could be a differential rectrix growth rate or and an order of rectrix growth. However, in nestling passerines, rectrices grow simultaneously Shirihai et al. Moreover, the yellow spots cover only ca. If growth rate varies between feathers, it seems unlikely that the region of the feather that erupts from feathers first would be affected.
Numerous studies have demonstrated that carotenoid-based traits bear important condition-dependent costs for their owners reviewed in Hill Environmental agents like access to dietary pigments, parasite infections, and nutritional state are the most important factors influencing plumage coloration change in the subsequent molt reviewed in Hill Moreover, carotenoid-based nuptial plumage coloration can be influenced by carotenoid or energy trade-offs associated with the use of carotenoids to either produce ornaments or aid in physiological processes e.
Comment 1. Today, I am discussing one of the well-known and frequently used patterns called the decorator design pattern. This takes place at compile time, and all of the instances of that class get the extended behavior. Decorator design patterns allow us to add functionality to an object not the class at runtime, and we can apply this customized functionality to an individual object based on our requirement and choice.
So, there is no change to the original class.
Decorator Design Pattern in Java
The decorator design pattern is structurally similar to the chain of responsibility pattern. Now, let's take a look at the decoration portion. I kept this abstract to avoid any direct instantiation since this is just a wrapper and does not add any functionality into the shape. Create LineStyleDecorator to add functionality of custom line styles in the shape. There you have it. I hope we are clear on the decorator design pattern now. Using the Adapter Design Pattern in Java. Using the Bridge Design Pattern in Java. Strategy vs. Factory Design Patterns in Java.
Decorator Design Pattern in Java. Over a million developers have joined DZone. Let's be friends:. DZone 's Guide to. Want to learn more about using the decorator design pattern in Java? Check out this example using the Shape class to learn how.