Evolutionary trade‐off between naturally‐ and sexually‐selected melanin‐based colour traits in worldwide barn owls and allies

Natural selection typically constrains the evolution of sexually‐selected characters. The evolution of naturally‐ and sexually‐selected traits can be intertwined if they share part of their genetic machinery or if sex traits impair foraging success or increase the risk of depredation. The present study investigated phenotypic correlations between naturally‐ and sexually‐selected plumage traits in the Tytonidae (barn owls, grass owls, and masked owls). Phenotypic correlations indicate the extent to which selection on one trait will indirectly influence the evolution of another trait. In this group of birds, the ventral body side varies from white to dark reddish, a naturally‐selected pheomelanin‐based colour trait with important roles in predator–prey interactions. Owls also exhibit eumelanin‐based black spots, for which number and size signal different aspects of individual quality and are used in mate choice. These three plumage traits are strongly heritable and sexually dimorphic, with females being on average darker reddish and more spotted than males. Phenotypic correlations were measured between these three plumage traits in 3958 free‐living barn owls in Switzerland and 10 670 skin specimens from 34 Tyto taxa preserved in museums. Across Tyto taxa, the sexually‐selected plumage spottiness was positively correlated with the naturally‐selected reddish coloration, with redder birds being more heavily spotted. This suggests that they are genetically constrained or that natural and sexual selection are not antagonistically exerted on plumage traits. In a large sample of Swiss nestlings and within 34 Tyto taxa, the three plumage traits were positively correlated. The production of melanin pigments for one plumage trait is therefore not traded off against the production of melanin pigments for another plumage trait. Only in the most heavily‐spotted Tyto taxa do larger‐spotted individuals display fewer spots. This indicates that, at some threshold value, the evolution of many spots constrains the evolution of large spots. These analyses raise the possibility that different combinations of melanin‐based plumage traits may not be selectively equivalent.     

Selection on a eumelanic ornament is stronger in the tropics than in temperate zones in the worldwide‐distributed barn owl

Spatial variation in the pattern of natural selection can promote local adaptation and genetic differentiation between populations. Because heritable melanin‐based ornaments can signal resistance to environmentally mediated elevation in glucocorticoids, to oxidative stress and parasites, populations may vary in the mean degree of melanic coloration if selection on these phenotypic aspects varies geographically. Within a population of Swiss barn owls (Tyto alba), the size of eumelanic spots is positively associated with survival, immunity and resistance to stress, but it is yet unknown whether Tyto species that face stressful environments evolved towards a darker eumelanic plumage. Because selection regimes vary along environmental gradients, we examined whether melanin‐based traits vary clinally and are expressed to a larger extent in the tropics where parasites are more abundant than in temperate zones. To this end, we considered 39 barn owl species distributed worldwide. Barn owl species living in the tropics displayed larger eumelanic spots than those found in temperate zones. This was, however, verified in the northern hemisphere only. Parasites being particularly abundant in the tropics, they may promote the evolution of darker eumelanic ornaments.     

Insularity and the evolution of melanism,sexual dichromatism and body size in the worldwide‐distributed barn owl

Island biogeography has provided fundamental hypotheses in population genetics, ecology and evolutionary biology. Insular populations usually face different feeding conditions, predation pressure, intraspecific and interspecific competition than continental populations. This so‐called island syndrome can promote the evolution of specific phenotypes like a small (or large) body size and a light (or dark) colouration as well as influence the evolution of sexual dimorphism. To examine whether insularity leads to phenotypic differentiation in a consistent way in a worldwide‐distributed nonmigratory species, we compared body size, body shape and colouration between insular and continental barn owl (Tyto alba) populations by controlling indirectly for phylogeny. This species is suitable because it varies in pheomelanin‐based colouration from reddish‐brown to white, and it displays eumelanic black spots for which the number and size vary between individuals, populations and species. Females are on average darker pheomelanic and display more and larger eumelanic spots than males. Our results show that on islands barn owls exhibited smaller and fewer eumelanic spots and lighter pheomelanic colouration, and shorter wings than on continents. Sexual dimorphism in pheomelanin‐based colouration was less pronounced on islands than continents (i.e. on islands males tended to be as pheomelanic as females), and on small islands owls were redder pheomelanic and smaller in size than owls living on larger islands. Sexual dimorphism in the size of eumelanic spots was more pronounced (i.e. females displayed much larger spots than males) in barn owls living on islands located further away from a continent. Our study indicates that insular conditions drive the evolution towards a lower degree of eumelanism, smaller body size and affects the evolution of sexual dichromatism in melanin‐based colour traits. The effect of insularity was more pronounced on body size and shape than on melanic traits.     

Geographic variation in sexual dimorphism in the barn owl Tyto alba: a role for direct selection or genetic correlation?

Geographic variation in sexually selected traits is commonly attributed to geographic variation in the net benefit accrued from bearing such traits. Although natural and sexual selection are potentially important in shaping geographic variation, genetic constraints may also play a role. Although a genetic correlation between two traits may itself be the outcome of natural or sexual selection, it may indirectly reinforce the establishment and maintenance of cline variation with respect to one particular trait when across the cline different values of other traits are selected. Using the barn owl Tyto alba, a species in which the plumage of females is more reddish‐brown and more marked with black spots than that of males, I report results that are consistent with the hypothesis that both direct selection and genetic constraints may help establish and maintain cline variation in sexual dichromatism. In this species, inter‐individual variation in plumage coloration and spottiness has a genetic basis, and these traits are not sensitive to the environment. Data, based on the measurement of skin specimens, is consistent with the hypothesis that the stronger European cline variation in male spottiness than in female spottiness depends on the combined effects of (1) the similar cline variation in male and female plumage coloration and (2) the more intense phenotypic correlation between plumage coloration and spottiness in males (darker birds are more heavily spotted in the two sexes, but especially males) which is a general feature among the globally distributed barn owls. In northern Europe, male and female T. a. guttata are reddish‐brown and heavily spotted, and in southern Europe male and female T. a. alba are white, but only females display many spots. Here, I discuss the relative importance of direct selection, genetic correlation and the post‐ice age invasion of Europe by T. alba, in generating sex‐specific cline variation in plumage spottiness and non‐sex‐specific cline variation in plumage coloration.     

Female barn owls (Tyto alba) advertise good genes

The good genes hypothesis of sexual selection postulates that ornamentation signals superior genetic quality to potential mates. Support for this hypothesis comes from studies on male ornamentation only, while it remains to be shown that female ornamentation may signal genetic quality as well. Female barn owls (Tyto alba) display more black spots on their plumage than males. The expression of this plumage trait has a genetic basis and it has been suggested that males prefer to mate with females displaying more black spots. Given the role of parasites in the evolution of sexually selected traits and of the immune system in parasite resistance, we hypothesize that the extent of female plumage 'spottiness' reflects immunological defence. We assessed the genetic variation in specific antibody production against a non-pathogenic antigen among cross-fostered nestlings and studied its covariation with the plumage spottiness of genetic parents. The magnitude of the antibody response was positively correlated with the plumage spottiness of the genetic mother but not of the genetic father. Our study thereby provides the first experimental support, to our knowledge, for the hypothesis that female ornamentation signals genetic quality.     

Age‐related change in melanin‐based coloration of Barn owls (Tyto alba): females that become more female‐like and males that become more male‐like perform better

Ornament expression fluctuates with age in many organisms. Whether these changes are adaptively plastic is poorly known. In order to understand the ultimate function of melanin‐based ornaments, we studied their within‐individual fluctuations and their covariation with fitness‐related traits. In barn owls (Tyto alba), individuals vary from reddish‐brown pheomelanic to white, and from immaculate to marked with black eumelanic spots, with males being less reddish and less spotted than females. During the first molt, both sexes became less pheomelanic, females displayed larger spots and males fewer spots, but the extent of these changes was not associated with reproduction. At subsequent molts, intra‐individual changes in melanin‐based traits covaried with simultaneous reproduction changes. Adult females bred earlier in the season and laid larger eggs when they became scattered with larger spots, whereas adults of both sexes produced larger broods when they became whiter. These results suggest that the production of melanin pigments and fitness‐related life‐history traits are concomitantly regulated in a sex‐specific way. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 689–704.     

A female melanin ornament signals offspring fluctuating asymmetry in the barn owl

Sexual selection theory predicts that males advertise quality by displaying extravagant ornaments. By contrast, whether phenotypic variation in females has a signalling function remains an open question. Here, to our knowledge, we provide the first evidence that a female plumage trait can signal fluctuating asymmetry in the offspring. We experimentally demonstrate in wild barn owls (Tyto alba) that the extent to which females display black spots on their plumage does not only signal offspring parasite resistance as shown in a previous study but also developmental homeostasis in the offspring. A greater number of spotted females produced offspring that had more symmetrical feathers during the period of growth. Males, that pair non-randomly with respect to female plumage spottiness therefore appear to gain substantial benefits by mating with heavily spotted females. Genetic variation in plumage spottiness is nevertheless maintained as the covariation between offspring body mass and mother plumage spottiness varies annually depending on environmental conditions.     

Why do melanin ornaments signal individual quality? Insights from metal element analysis of barn owl feathers

Melanin-based variation in colour patterns is under strong genetic control and not, or weakly, sensitive to the environment and body condition. Current signalling theory predicts that such traits may not signal honestly phenotypic quality because their production does not entail a significant fitness cost. However, recent studies revealed that in several bird species melanin-based traits covary with phenotypic attributes. In a first move to understand whether such covariations have a physiological basis, we quantified concentrations of five chemical elements in two pigmented plumage traits in the barn owl (Tyto alba). This bird shows continuous variation from immaculate to heavily marked with black spots (plumage spottiness) and from dark reddish-brown to white (plumage coloration), two traits that signal various aspects of individual quality. These two traits are sexually dimorphic with females being spottier and darker coloured than males. We found an enhancement in calcium and zinc concentration within black spots compared with the unspotted feather parts. The degree to which birds were spotted was positively correlated with calcium concentration within spots, whereas the unspotted feather parts of darker reddish-brown birds were more concentrated in zinc. This suggests that two different pigments are responsible for plumage spottiness and plumage coloration. We discuss the implications of our results in light of recent experimental field studies showing that female spottiness signals offspring humoral response towards an artificially administrated antigen, parasite resistance and fluctuating asymmetry of wing feathers.An erratum to this article can be found at     

Sex‐linked inheritance,genetic correlations and sexual dimorphism in three melanin‐based colour traits in the barn owl

Theory states that genes on the sex chromosomes have stronger effects on sexual dimorphism than genes on the autosomes. Although empirical data are not necessarily consistent with this theory, this situation may prevail because the relative role of sex‐linked and autosomally inherited genes on sexual dimorphism has rarely been evaluated. We estimated the quantitative genetics of three sexually dimorphic melanin‐based traits in the barn owl (Tyto alba), in which females are on average darker reddish pheomelanic and display more and larger black eumelanic feather spots than males. The plumage traits with higher sex‐linked inheritance showed lower heritability and genetic correlations, but contrary to prediction, these traits showed less pronounced sexual dimorphism. Strong offspring sexual dimorphism primarily resulted from daughters not expressing malelike melanin‐based traits and from sons expressing femalelike traits to similar degrees as their sisters. We conclude that in the barn owl, polymorphism at autosomal genes rather than at sex‐linked genes generate variation in sexual dimorphism in melanin‐based traits.     

Similar patterns of local barn owl adaptation in the Middle East and Europe with respect to melanic coloration

The maintenance of phenotypic variation is a central question in evolutionary biology. A commonly suggested mechanism is that of local adaptation, whereby different phenotypes are adapted to alternative environmental conditions. A recent study in the European barn owl (Tyto alba) has shown that natural selection maintains a strong clinal variation in reddish pheomelanin‐based coloration. Studies in the region where phenotypic variation in this owl is the highest in Europe have further demonstrated that dark‐reddish and pale‐reddish owls exploit open and wooded habitats, predate voles and wood mice, and are long‐tailed and short‐tailed, respectively. However, it remains unclear as to whether these traits evolved as a consequence of allopatric evolution of dark colour in northern Europe and white colour in southern Europe, during which owls could have also evolved different morphologies and foraging behaviour. This scenario implies that covariation between coloration and foraging behaviour could be a specificity of the European continent, which is not found in other worldwide‐distributed populations. To investigate this issue, we studied a barn owl population in the Middle East. The results obtained show that, as in Central Europe, dark‐reddish female owls breed more often in the open landscape than their pale‐reddish female conspecifics, their offspring are fed with more voles than Muridae, and they are longer‐winged and longer‐tailed. These findings indicate that, in the barn owl, the association in females between pheomelanin‐based coloration and foraging behaviour and morphology is not restricted to the European continent but may well evolve in sympatry in many barn owl populations worldwide. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106 , 447–454.     

Temporal variation in glucocorticoid levels during the resting phase is associated in opposite way with maternal and paternal melanic coloration

Sex‐dependent selection can help maintain sexual dimorphism. When the magnitude of selection exerted on a heritable sex trait differs between the sexes, it may prevent each sex to reach its phenotypic optimum. As a consequence, the benefit of expressing a sex trait to a given value may differ between males and females favouring sex‐specific adaptations associated with different values of a sex trait. The level of metabolites regulated by genes that are under sex‐dependent selection may therefore covary with the degree of ornamentation differently in the two sexes. We investigated this prediction in the barn owl, a species in which females display on average larger black spots on the plumage than males, a heritable ornament. This melanin‐based colour trait is strongly selected in females and weakly counter‐selected in males indicating sex‐dependent selection. In nestling barn owls, we found that daily variation in baseline corticosterone levels, a key hormone that mediates life history trade‐offs, covaries with spot diameter displayed by their biological parents. When their mother displayed larger spots, nestlings had lower corticosterone levels in the morning and higher levels in the evening, whereas the opposite pattern was found with the size of paternal spots. Our study suggests a link between daily regulation of glucocorticoids and sex‐dependent selection exerted on sexually dimorphic melanin‐based ornaments.     

Is the denser contour feather structure in pale grey than in pheomelanic brown tawny owls Strix aluco an adaptation to cold environments?

In colour polymorphic species morphs are considered to be adaptations to different environments, where they have evolved and are maintained because of their differential sensitivity to the environment. In cold environments the plumage insulation capacity is essential for survival and it has been proposed that plumage colour is associated with feather structure and thereby the insulation capacity of the plumage. We studied the structure of contour feathers in the colour polymorphic tawny owl Strix aluco. A previous study of tawny owls in the same population has found strong selection against the brown morph in cold and snowy winters whereas this selection pressure is absent in mild winters. We predicted that grey morphs have a denser and more insulative plumage, enabling them to survive better in cold climate compared to brown ones. The insulative plumulaceous part of the dorsal contour feathers was larger and the fine structure of the plumulaceous part of the feather was denser in grey tawny owls than in brown ones. In the ventral contour feathers the plumulaceous part of the feather was denser in females than in males and in older birds without any differences between morphs. Our study suggests that insulative microscopical feather structures differ between colour morphs and we propose that feather structure may be a trait associated with morph‐specific survival in cold environments.     

Female‐ and male‐specific signals of quality in the barn owl

Most bird studies of female signalling have been confined to species in which females display a male‐ornament in a vestigial form. However, a great deal of benefit may be gained from considering phenotypic traits that are specific to females. This is because (1) sex‐specific traits may signal sex‐specific qualities and (2) females may develop a male‐ornament not because they are selected to do so, but because fathers transmit to daughters the underlying genes for its expression (genetic correlation between the sexes). We investigated these two propositions in the barn owl Tyto alba, a species in which male plumage is lighter in colour and less marked with black spots than that of females. Firstly, we present published evidence that female plumage spottiness reflects parasite resistance ability. We also show that male plumage coloration is correlated with reproductive success, male feeding rate and heart mass. Secondly, cross‐fostering experiments demonstrate that plumage coloration and spottiness are genetically correlated between the sexes. This implies that if a given trait value is selected in one sex, the other sex will indirectly evolve towards a similar value. This prediction is supported by the observation that female plumage coloration and spottiness resembled that of males, in comparisons at the level of Tyto alba alba populations, Tyto alba subspecies and Tyto species. Our results therefore support the hypothesis that sex‐specific traits signal sex‐specific qualities and that a gene for a sex‐specific trait can be expressed in the other sex as the consequence of a genetic correlation between the sexes.     

Proximate basis of the covariation between a melanin-based female ornament and offspring quality

In contradiction to sexual selection theory, several studies showed that although the expression of melanin-based ornaments is usually under strong genetic control and weakly sensitive to the environment and body condition, they can signal individual quality. Covariation between a melanin-based ornament and phenotypic quality may result from pleiotropic effects of genes involved in the production of melanin pigments. Two categories of genes responsible for variation in melanin production may be relevant, namely those that trigger melanin production (yes or no response) and those that determine the amount of pigments produced. To investigate which of these two hypotheses is the most likely, I reanalysed data collected from barn owls (Tyto alba). The underparts of this bird vary from immaculate to heavily marked with black spots of varying size. Published cross-fostering experiments have shown that the proportion of the plumage surface covered with black spots, a eumelanin composite trait so-called plumage spottiness, in females positively covaries with offspring humoral immunocompetence, and negatively with offspring parasite resistance (i.e. the ability to reduce fecundity of ectoparasites) and fluctuating asymmetry of wing feathers. However, it is unclear which component of plumage spottiness causes these relationships, namely genes responsible for variation in number of spots or in spot diameter. Number of spots reflects variation in the expression of genes triggering the switch from no eumelanin production to production, whereas spot diameter reflects variation in the expression of genes determining the amount of eumelanin produced per spot. In the present study, multiple regression analyses, performed on the same data sets, showed that humoral immunocompetence, parasite resistance and wing fluctuating asymmetry of cross-fostered offspring covary with spot diameter measured in their genetic mother, but not with number of spots. This suggests that genes responsible for variation in the quantity of eumelanin produced per spot are responsible for covariation between a melanin ornament and individual attributes. In contrast, genes responsible for variation in number of black spots may not play a significant role. Covariation between a eumelanin female trait and offspring quality may therefore be due to an indirect effect of melanin production.     

The genetic basis of color‐related local adaptation in a ring‐like colonization around the Mediterranean

Uncovering the genetic basis of phenotypic variation and the population history under which it established is key to understand the trajectories along which local adaptation evolves. Here, we investigated the genetic basis and evolutionary history of a clinal plumage color polymorphism in European barn owls (Tyto alba). Our results suggest that barn owls colonized the Western Palearctic in a ring‐like manner around the Mediterranean and meet in secondary contact in Greece. Rufous coloration appears to be linked to a recently evolved nonsynonymous‐derived variant of the melanocortin 1 receptor (MC1R) gene, which according to quantitative genetic analyses evolved under local adaptation during or following the colonization of Central Europe. Admixture patterns and linkage disequilibrium between the neutral genetic background and color found exclusively within the secondary contact zone suggest limited introgression at secondary contact. These results from a system reminiscent of ring species provide a striking example of how local adaptation can evolve from derived genetic variation.     

Nonrandom pairing by male barn owls (Tyto alba) with respect to a female plumage trait

In socially monogamous species it is rare for females to bemore intensely colored than males. The barn owl (Tyto alba)is one of the exceptions, as females usually exhibit more andlarger black spots on the plumage. The evolution of sexual dimorphismin plumage traits is commonly assumed to be the result of sexualselection. I therefore examined the prediction that male barnowls do not pair randomly with respect to female plumage spottinessduring a 5-year study in Switzerland. The prediction was supported,as males that changed mates acquired a new female that was similarlyspotted to the previous one, and pairing with respect to plumage spottinesswas positively assortative. Significant repeatability in male pairingwas presumably neither the consequence of sharing the same habitats withfemales displaying a given plumage spottiness nor of morphological characteristicsof the males that could influence mate sampling. A resemblance inplumage spottiness between the mates of sons and of their fathersuggests that repeatability could have resulted from sexualimprinting and/or heritable variance in male preference forspotted females. To test whether males assess female plumagespottiness, I either cut off black spots or small pieces of feathersbut not the spots of already mated females. Males mated to females withreduced plumage spottiness fed their brood at a lower cadencyand achieved a lower reproductive success than other males.This experiment further suggests that female plumage spottinessis a stimulus for males.     

The evolution of plumage polymorphism in birds of prey and owls: the apostatic selection hypothesis revisited

Co-evolution between phenotypic variation and other traits is of paramount importance for our understanding of the origin and maintenance of polymorphism in natural populations. We tested whether the evolution of plumage polymorphism in birds of prey and owls was supported by the apostatic selection hypothesis using ecological and life-history variables in birds of prey and owls and performing both cross taxa and independent contrast analyses. For both bird groups, we did not find any support for the apostatic selection hypothesis being the maintaining factor for the polymorphism: plumage polymorphism was not more common in taxa hunting avian or mammalian prey, nor in migratory species. In contrast, we found that polymorphism was related to variables such as sexual plumage dimorphism, population size and range size, as well as breeding altitude and breeding latitude. These results imply that the most likely evolutionary correlate of polymorphism in both bird groups is population size, different plumage morphs might simply arise in larger populations most likely because of a higher probability of mutations and then be maintained by sexual selection.     

GENETIC,ENVIRONMENTAL, AND CONDITION-DEPENDENT EFFECTS ON FEMALE AND MALE ORNAMENTATION IN THE BARN OWL TYTO ALBA

Secondary sexual characters are thought to indicate individual quality. Expression of sex-limited traits in an extravagant state may require both the underlying genes and the available nutrient resources. The assessment of the relative contribution of genes, environment, and body condition is relevant for understanding to that extent the extravagant trait may signal genotypic or phenotypic quality of the individual. In birds, usually only the males are ornamented. In the barn owl, Tyto alba, both females and males display sex-limited plumage traits. Males are commonly lighter colored and females spottier. In an experiment with combined cross-fostering and brood size manipulation we determined the relative contribution of genes, environment, and body condition to the variation in plumage coloration and plumage spottiness. The partial cross-fostering experiment tested the relative importance of shared genes and a shared environment for the resemblance of related birds. Siblings raised in different nests converged toward similar trait values, offspring resembled the true but not the foster parents, and plumage traits of unrelated nestlings sharing the same nest were not correlated. Results were not inflated by maternal effects detectable in the mother's phenotype, because middaughter to mother resemblance was not higher than midson to father resemblance. This suggests that plumage coloration and spottiness are largely genetically inherited traits, and that the rearing environment does not have a strong impact on the expression of these traits. To further investigate whether the two sex-limited traits are condition dependent, brood sizes were manipulated. Enlargement or reduction of broods by two nestlings resulted in lower and higher body mass of nestlings, respectively. However, nestlings raised in enlarged or reduced broods did not show either a significantly darker or lighter or a more or less spotted plumage. We did not detect any genotype-by-environment interaction. In conclusion, simultaneous cross-fostering and brood size manipulation demonstrate that additive genetic variance for plumage coloration and spottiness is maintained and that both the rearing environment and body condition do not account for a large proportion of the phenotypic variance in female and male ornamentations.     

Genetic and environmental components of variation in eumelanin and phaeomelanin sex-traits in the barn owl

Knowledge of the mechanism underlying the expression of melanin-based sex-traits may help us to understand their signalling function. Potential sources of inter-individual variation are the total amount of melanins produced but also how biochemical precursors are allocated into the eumelanin and phaeomelanin pigments responsible for black and reddish-brown colours, respectively. In the barn owl (Tyto alba), a eumelanin trait (referred to as 'plumage spottiness') signals immunocompetence towards an artificially administrated antigen and parasite resistance in females, whereas a phaeomelanin trait ('plumage coloration') signals investment in reproduction in males. This raises the question whether plumage coloration and spottiness are expressed independent of each other. To investigate this question, we have studied the genetics of these two plumage traits. Crossfostering experiments showed that, for each trait, phenotypic variation has a strong genetic component, whereas no environmental component could be detected. Plumage coloration is autosomally inherited, as suggested by the similar paternal-to-maternal contribution to offspring coloration. In contrast, plumage spottiness may be sex-linked inherited (in birds, females are heterogametic). That proposition arises from the observation that sons resembled their mother more than their father and that daughters resembled only their father. Despite plumage coloration and spottiness signalling different qualities, these two traits are not inherited independent of each other, darker birds being spottier. This suggests that the extent to which coloration and spottiness are expressed depends on the total amount of melanin produced (with more melanin leading to a both darker and spottier plumage) rather than on differential allocation of melanin into plumage coloration and spottiness (in such a case, darker birds should have been less spotted). A gene controlling the production of melanin pigments may be located on sex-chromosomes, since the phenotypic correlation between coloration and spottiness was stronger in males than in females.     

Une nouvelle forme insulaire d'Effraie geanteTyto balearica N. sp., (Aves,Strigiformes), du Plio-Pleistocene des Baleares

Tyto balearica is a barn owl whose size is about one and half larger than the size of modern barn owls, Tyto alba. It was found in Mallorca and Menorca, in sites dating back from the end of Pliocene and the beginning of Pleistocene. Numerous insular forms of giant barn owls are known in Mediterranean islands and in West Indies.