Academic literature on the topic 'Cryptic plumage'

Why does the European Blackbird’s dark coloration match the ground color of the less widespread of its breeding habitats, the riparian forest, although its main European population occurs in the pale-litter woodland? It is argued that crypsis of all the age stages was more necessary in riparian stands, as this habitat is more risky for the species owing to a high ground vegetation surrounding a foraging bird. Poorer crypsis of Blackbird plumage in pale-litter habitats may be a neutral feature, being compensated by easier scanning of the surroundings over the lower and sparcer herb vegetation and by a tendency to remain in dark sites. The black plumage of the Blackbird male, perhaps reinforced by sexual selection in pristine forest conditions may also retain its cryptic function.
 Keywords: Dark/black plumage, crypsis, primeval habitat, European Blackbird Turdus merula.

Sexual signals often compromise camouflage because of their conspicuousness. Pigmentation patterns, on the contrary, aid in camouflage. It was hypothesized that a particular type of pattern—barred plumage in birds, whereby pigmented bars extend across feathers—could simultaneously signal individual quality, because disruptions of these patterns should be perceptually salient at close range and help assess plumage condition. Here we show that common waxbills ( Estrilda astrild ), which have extensive barred plumage, have more regular patterns as adults than as juveniles, and that adult males have more regular patterns than females. Both these differences are indicative of sexual signalling in species with conventional sex roles. More regular barred plumage was related to better body condition in adult males. Colour ornamentation traits were also related to aspects of quality, either the same as barred plumage (body condition) or a different one (good feather development), supporting both the ‘redundant message’ and the ‘multiple message’ hypotheses for the coexistence of multiple sexual signals. Although receiver responses to the regularity of barred plumage were not studied here, research on other species has shown that barred plumage can mediate social interactions. We conclude that using barred plumage as a signal of quality helps circumvent the functional compromise between camouflage and communication.

Abstract I used data from two breeding populations of Black-headed Grosbeaks (Pheucticus melanocephalus) in central New Mexico to test alternative hypotheses regarding the function of delayed plumage maturation in male passerines. Yearling male grosbeaks displayed a wide range of subadult plumage types, but most individuals were intermediate in appearance between adult males and females. Subadult male grosbeaks arrived on the study sites about 2 weeks after adult males, with no tendency for individuals with brighter or duller plumage to arrive first. Only a few of the most brightly plumaged subadult males defended territories and attracted females; most were nonterritorial floaters. All territories of subadult males were positioned outside clusters of adult male territories with few total neighbors. When I removed adult males from their territories, the territories remained empty. These results are not consistent with predictions of the female-mimicry hypothesis, but they are in accord with those of the cryptic hypothesis.

Abstract We studied the patterns of sexual dichromatism and seasonal variation in plumage color in the Diademed Tanager (Stephanophorus diadematus), a species previously considered devoid of variation in adult plumage. The general coloration of this species is dark blue-violet, with a white-blue and red crown. Plumage reflectance of seven body regions from 33 study skins belonging to adults of both sexes was measured. Reflectance values were used in a principal components analysis (PCA) and hue, short-wave chroma, and UV chroma were also measured directly on the spectra. Both PCA factor scores and these latter variables were subjected to two-way ANCOVAs with sex and season as main factors and the year of capture as a covariate. We found that crowns of males were significantly brighter than those of females. In addition, the nape, chest, and belly showed significant differences in spectral shape, with relatively greater short-wave reflectance and less long-wave reflectance in males than in females. Although sexes were alike in hue, they differed in chroma in almost all body regions. Brightness also differed between seasons, and contrary to our expectation nonbreeding birds were brighter than breeding ones. This result may be a consequence of the particular molt program of tanagers that includes only a complete post-reproductive molt. Despite finding seasonal differences in spectral shape in various body regions, no significant changes in hue, short-wave chroma, or UV chroma were evident. To our knowledge, this is the first report of variation in adult plumage color for the Diademed Tanager, and we suggest that dichromatism in tanagers may be even more pervasive than is currently recognized. Dicromatismo Críptico y Variación Estacional de Color en Stephanophorus diadematus Resumen. Estudiamos los patrones de dicromatismo sexual y variación estacional en la coloración del plumaje de Stephanophorus diadematus, una especie previamente considerada carente de variación en la coloración del plumaje adulto. La coloración general de esta especie es azul violáceo oscuro, con una corona blanca azulada y roja. Se midió la reflectancia de siete regiones corporales en 33 pieles de estudio pertenecientes a adultos de ambos sexos. Los valores de reflectancia se utilizaron en un análisis de componentes principales, y además se midieron el tono (hue), la intensidad del color de onda corta y la intensidad del color de UV directamente sobre los espectros. Tanto los factores del análisis de componentes principales como las variables mencionadas fueron sujetos a ANCOVAs de dos factores, considerando el sexo y la estación como factores principales, y el año de captura como covariable. Estos análisis mostraron que la corona de los machos es significativamente más brillante que la de las hembras. Además, la nuca, el pecho y el vientre mostraron diferencias significativas en la forma espectral, presentando los machos mayor reflectancia en la zona de onda corta y menor en la zona de onda larga que las hembras. Si bien el tono no difirió entre sexos, la intensidad del color difirió en la mayoría de las regiones corporales entre machos y hembras. El brillo también difirió entre temporadas y, contrariamente a nuestra expectativa, los individuos capturados en la temporada no reproductiva fueron más brillantes que aquellos capturados en la temporada reproductiva. Este resultado podría deberse al programa de muda particular presente en Thraupidae, que incluye una única muda post-reproductiva completa. Si bien encontramos diferencias entre estaciones en la forma espectral en varias regiones corporales, no se detectaron diferencias en el tono, la intensidad del color de onda corta ni la intensidad del color de UV. Este es, de acuerdo a nuestro conocimiento, el primer estudio que muestra variación en la coloración del plumaje adulto de S. diadematus. Sugerimos que el dicromatismo en Thraupidae podría ser más común de lo que actualmente se piensa.

Abstract Natural and sexual selection drive colour evolution in animals. However, these different selective forces are often studied independently or without considering environmental variation. We evaluated the roles of natural and sexual selection together on colour evolution in 15 sympatric wood-warbler species, while considering the influence of variation in the light environment and visual background. We tested the influence of each selective pressure on male and female coloration and contrast against the background using avian visual models in phylogenetically controlled analyses. We found natural and sexual selection simultaneously driving cryptic and conspicuous plumage in males by acting on different body regions. For example, we found that ground-nesting species had males with conspicuous under-body plumage and cryptic upper-body plumage, showing how natural and sexual selection can drive colour evolution concordantly. We also found interesting relationships with female plumage, such as nest predation positively covarying with female contrast against the background, suggesting a cost to female conspicuousness. Our findings here showcase the complexity of selection on coloration and illustrate the importance of: (1) accounting for environmental variation when assessing how natural and sexual selection drive colour evolution; and (2) testing how multiple selection pressures are shaping colour diversity among species.

Most drab plumage colours are probably cryptic. Crypsis (camouflage) occurs when the colour of a significant part of the plumage is similar to the colour of a significant part of the background against which the prey bird may be detected by a potential predator. In this study we compare back colours of tits and associated species with colour backgrounds in their habitat during a four-month period in winter. We test the hypothesis that in some of the species back colour is similar to one of the background colours. In addition to colour backgrounds, microhabitats and tree species were also recorded. Great Tit Parus major, Nuthatch Sitta europea and Treecreeper Certhia familiaris showed distinct preferences for different colour backgrounds, reflecting their choice of microhabitats and tree species. The data suggest that in the Great Tit the olive-moss green back colour has evolved as crypsis for foraging close to the base of tree trunks, where most of the moss is found. The bluish-grey back colour of the Nuthatch is suggested to have evolved as crypsis against greyish beech trunks and branches. Similarly the brown back colour of the Treecreeper is suggested to have evolved as crypsis against pale brown- greyish brown bark surfaces. The possibility that the grey back colour of the Marsh Tit Parus palustris has evolved as crypsis against greyish branches is discussed. For the Blue Tit Parus caeruleus it is suggested that the green back colour has evolved as crypsis against leaves during summer; thus no background matching of the back occurs in winter. For the black back colour of the Longtailed Tit Aegithalos caudatos no background matching can be suggested. The study demonstrates that it is possible to quantify background colours for fouraging birds in the wild as seen by a human observer on the ground. It is proposed that these observations are also representative for a hunting Sparrowhawk Accipiter nisus, even though differences in observing height and possible differences in spectral visual range may present difficulties.
 Key words:. Plumage colour, background colour, crypsis, Great Tit Parus major, Blue Tit Parus caeruleus, Marsh Tit Parus palustris, Nuthatch Sitta europaea, Treecreeper Certhia familiaris.

Populations in the Rufous Antpitta (Grallaria rufula) complex occupy humid montane forests of the Andes from northern Colombia and adjacent Venezuela to central Bolivia. Their tawny to cinnamon-colored plumages are generally uniform, featuring subtle variation in hue and saturation across this range. In contrast to their conservative plumage, substantial vocal differences occur among geographically isolated or parapatric populations. Working within the framework of a comprehensive molecular phylogeny, we reexamined species limits in the G. rufula complex, basing taxonomic recommendations on diagnostic differences in vocalizations and considering identifiable differences in plumage where pertinent. We identified 16 populations for species designation, including seven populations previously described as subspecies and, remarkably, six new species described herein. Within one of these species, we identified less robust vocal differences between populations that we designate as subspecies. Geographic variation exists within another species, but its critical evaluation requires additional material. Taxonomic revisions of groups consisting of cryptic species, like the Grallaria rufula complex, are imperative for their conservation. Rather than widespread species as currently defined, these complexes can comprise many range-restricted taxa at higher risk of extinction given the continuing human pressures on their habitats.

Abstract Camouflage is widespread throughout the animal kingdom allowing individuals to avoid detection and hence save time and energy rather than escape from an approaching predator. Thus, camouflage is likely to have co-evolved with antipredator behavior. Here, we propose that camouflage results in dichotomous escape behavior within and among species with classes of individuals and species with cryptic coloration having shorter flight initiation distances (FIDs; the distance at which an individual takes flight when approached by a human). We report the results of 2 tests of this hypothesis. First, bird species with cryptically colored plumage have consistently shorter FID than closely related species without such color. Within species with sexually dimorphic plumage, brightly colored adult male common pheasants Phasianus colchicus and golden pheasants Chrysolophus pictus have long and variable FID, whereas cryptically colored juveniles and adult females have short and invariable FID. Second, FID in females was predicted by presence or absence of cryptic color, FID in males and their interaction. These findings are consistent with the hypothesis that risk-taking behavior has been attuned to camouflage, and that species with different levels of camouflage differ consistently in their FID.

The Chestnut-backed Button-quail Turnix castanotus is a small, cryptic, ground-dwelling species endemic to savanna ecosystems of northern Australia. Due to aspects of its ecology, cryptic plumage and behaviour, and the remoteness of most of its distribution, there are few published observations from the field documenting its breeding biology. The eggs were first described in 1856 and have subsequently been described by other authors. Two nests were detected in the Northern Territory in March 2021. We compare nesting events there with previous descriptions and museum collections. Our findings are mostly consistent with other literature on this species, but are inconsistent with two contemporary accounts, which we suggest are based on misidentification of Painted Button-quail T. varius.

Abstract One of the most important findings of this study is that male and female behaviour makes good adaptive sense in terms of maximising individual reproductive success (Chapter 9). The first reaction of a colleague was: ‘Well, those dunnocks must be very clever to work out all the reproductive payoffs in Table 9.4!’ The standard reply is that the animals themselves need not be aware of the consequences of their actions. The dunnock’s cryptic plumage has presumably evolved without individuals being aware of exactly how the crypsis works. In the same way, behavioural strategies can evolve without individuals working out all the costs and benefits. It is natural selection which judges the success of alternative strategies, favouring those which best promote an individual’s reproductive success, the means by which genes programming those strategies proliferate in the population. Individuals may play their strategies unconsciously, as programmed by their genetic and physiological make-up; this will influence, for example, plumage colour, the tendency to be aggressive to rivals, work rate in chick feeding, and so on.

Abstract The traditional explanation for interspecific variation in the extent of sexual dimorphism among birds is that it is a consequence of variation among species in social mating system and the pattern of parental care (from Darwin 1871 and Wallace 1889 onwards; reviewed in Lack 1968; Butcher and Rohwer 1988; Andersson 1994). For example, social polygamy leads to the competitive sex being larger and more ornate than the choosy sex, whereas large sex differences in parental care leads to the caring sex developing more cryptic plumage. Recently, however, two empirical observations have challenged this traditional view. First, many extremely polygamous species in which one sex cares for the offspring alone are, in fact, largely monomorphic with respect to both size and plumage colour (Hoglund 1989; Trail 1990; but see Oakes 1992). But even more strikingly, many apparently monogamous species that display classic biparental care are, in fact, highly dimorphic (Moller 1986; Harvey and Bradbury 1991).