The niche divergence hypothesis proposes that the evolution and maintenance of colour polymorphism is based on a mechanism of disruptive selection. In a trophic context, the hypothesis predicts that ...individuals differing in colour vary in their trophic niche, either because they differ in foraging efficiency or feed in different habitats. A major evolutionary conundrum is how these expectations are affected by variation in trophic quality. Using an owl species with colour plumage polymorphism, the Eurasian scops owl
Otus scops
, we examined diet and habitat segregation during reproduction in relation to plumage colouration and trophic quality. Intensive sampling revealed that trophic quality for scops owls (i.e. abundance of grasshoppers and locusts) varied more among territories than between years, but scops owls did not segregate among territories of different quality by their colouration. However, we found that sex, plumage colouration and territory differences in trophic quality explained differences in the degree of dietary specialization. Brownish males delivered a higher diversity of prey to the nest than greyish ones in high trophic quality territories. We also found that the more diverse the diet provided by males, the heavier the owlets at fledging. Our study provides evidence for a different sensitivity to trophic quality of the colour morphs with potential fitness consequences in scops owls. We highlight the importance of studying the mechanisms leading to the persistence of colour polymorphism in patchy environments, since segregation may pass otherwise unnoticed if only habitats or years with similar conditions are considered.
Detectability of morphs in different light environments is one of the mechanisms favoring the persistence of color polymorphism via disruptive selection. This mechanism predicts that different morphs ...should be more active and successful when light conditions make them more cryptic. In nocturnal birds, no study has analyzed yet whether morphs show a different degree of nocturnality, showing different circadian activity rhythms in relation to night and day light. We analyze activity patterns and hunting efficiency of color morphs in relation to day/night light in the nocturnal polymorphic scops owl (
Otus scops
). Forty-four percent of owl activity took place in the first hours after sunrise and before sunset. Also, we found that nocturnal activity decreased from grey to brown females and that grey males fed their chicks more than brown ones at night. Visual modeling revealed that grey individuals would be more conspicuous to their prey than brownish ones during the day. These findings suggest that part of the activity of nocturnal scops owls may occur during the day and that grey individuals would be better adapted to forage during night-light than brownish ones. However, brown morphs seemed not to be better adapted to forage at day, suggesting that other mechanisms than visual detection by predators or prey contribute to the persistence of color polymorphism in the species.
Significance statement
Circadian activity patterns can vary intraspecifically in response to changing environmental conditions. Color variants in polymorphic species could change their circadian activity rhythms differently in relation to diel luminal variation, switching from nocturnality to diurnality or vice versa, to achieve better background matching. We study for the first time whether different color variants of the nocturnal polymorphic scops owl (
Otus scops
) show different circadian activity rhythms with respect to night and day light conditions by relying on GPS-tracking data and nest video recordings. We also use perceptual visual modeling to study crypsis of morphs during the day. We found that nearly half of the activity of owls took place in the first hours after sunrise and before sunset. Also, we found that grey individuals would be better adapted to forage during night-light than more brownish ones probably due to their poor background matching during the day for the visual system of insects. These results support the idea that in scops owls, color morphs may show different degree of nocturnality to improve their crypsis.
We present the complete genome sequence of an aviadenovirus obtained by metagenomics from cloacal swabs taken from a free-living Eurasian scops owl (
Otus scops
, a small raptor distributed in Europe ...and several parts of Asia) in China. Thirty protein coding genes were predicted in this 40,239-bp-long genome, which encodes the largest fiber protein among all reported aviadenoviruses. The viral genome sequence is highly divergent, and the encoded proteins have an average of only 55% amino acid sequence identity to those of other adenoviruses. In phylogenetic analysis, the new owl virus grouped with members of the genus
Aviadenovirus
and formed a common clade with another owl adenovirus reported previously in Japan. This is the second complete genome sequence of an aviadenovirus discovered in owls, and its proteins have an average of 62% amino acid sequence identity to those of the previously reported owl adenovirus. Combining this result with comparative genomic analysis of all aviadenoviruses, we propose that this owl virus and the previously described Japanese owl adenovirus can be assigned to two new species in the genus
Aviadenovirus
. This study provides new data on the diversity of aviadenoviruses in wild birds.
Urbanization is often associated with homogenization, including the homogenization of biodiversity and overpopulation by generalist species that can change community and disease dynamics. In Madrid, ...nestlings of Eurasian Scops Owl Otus scops frequently suffer necrotic oropharyngeal disease as a result of infection by Gongylonema sp., a parasitic nematode transmitted by adult owls to their offspring through the diet, more specifically through consumption of a pest species: the oriental cockroach Blatta orientalis. We studied how the presence of cockroaches and owl infection rates are affected by urban features such as green areas. We found that a higher number of birds were affected by the parasite in the initial period of the breeding season and in areas with greater surface area of green spaces. We suggest that urban management should promote the diversity of insects in green areas so that the owls diversify their dietary offer to their offspring, to reduce the prevalence of the disease and improve their breeding success in the city of Madrid, as this problem has not yet been described in other cities.
In several animal species, including birds, individuals are known to produce low‐frequency vocalizations during aggressive interactions with conspecifics. In this study, I investigated territorial ...interactions between male Eurasian Scops Owls Otus scops that occupied territories in a densely packed area. The single‐note hoot of the Scops Owl is generally thought to be highly repeatable; however, extensive recording of male–male interactions identified previously unrecognized variation in the structure of hoots. Male Scops Owls gave hoots at a frequency lower than usual when engaging in short‐distance contests with neighbouring males. Within‐subject analysis revealed that the caller’s average hoot frequency was positively correlated with the distance from its rival. During contests, males gradually reduced their hoot frequency as they approached one another, perhaps reflecting changes in the degree of escalation. Furthermore, there is evidence that male Scops Owls have voluntary control of their hoot frequency also on a very short time scale. Males gave deeper hoots immediately after the rival initiated countersinging, and returned to their usual frequency range at the end of the interaction. This study confirms in part the findings of other authors’ experimental work, where male owls adjusted their vocal frequency when challenged by an opponent. However, that study suggested that vocal frequency would encode information about the caller’s bodyweight. In contrast, the results of the present study cannot exclude the hypothesis that the hoot of the Scops Owl is a variable, conventional signal that reflects the willingness to escalate the conflict. The reliability of the signal could be maintained by the risk of retaliation by the opponent, usually located a few metres from the caller.
Individuals within populations often show consistent variation in behavioural and physiological traits which are frequently inter-correlated, potentially leading to phenotypic integration. ...Understanding the mechanisms behind such integration is a key task in evolutionary ecology, and melanin based colouration has been suggested to play a pivotal role. In birds, most of plumage colour variation is determined by two types of melanin, eumelanin and phaeomelanin, but the role of phaeomelanin in avian phenotype integration has been barely investigated. Here, we test for covariation between phaeomelanin-based colouration, behavioural traits (i.e. nest territoriality, aggressiveness, breath rate and parental behaviour) and corticosterone in feathers in the polymorphic scops owl Otus scops, a bird species in which more phaeomelanic individuals display reddish colourations. In males, we observed that reddish males took longer to return to their nests and showed higher levels of feather CORT than more greyish ones. Behaviour and feather CORT were not associated to plumage colour in females. The found associations between redness, behaviour and feather CORT in males, but not in females, might suggest the existence of a sex-specific integrated phaeomelanic phenotype in scops owls.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
In Europe, agricultural practices have progressively evolved towards high productivity leading either to the intensification of productive and accessible areas or to the abandonment of less ...profitable sites. Both processes have led to the degradation of semi‐natural habitats like extensive grasslands, threatening species such as the Eurasian Scops Owl Otus scops that rely on extensively managed agricultural landscapes. In this work, we aimed to assess the habitat preferences of the Scops Owl using habitat suitability models combined with a multi‐scale approach. We generated a set of multi‐scale predictors, considering both biotic and abiotic variables, built on two newly developed vegetation management and orthopteran abundance models. To select the variables to incorporate in a ‘best multi‐scale model’, we chose the best spatial scale for each variable using univariate models and by calculating their relative importance through multi‐model inference. Next, we built ensembles of small models (ESMs) at 10 different scales from 50 to 1000 m, and an additional model with each variable at its best scale (‘best multi‐scale model’). The latter performed better than most of the other ESMs and allowed the creation of a high‐resolution habitat suitability map for the species. Scops Owls showed a preference for dry sites with extensive and well‐structured habitats with 30–40% bush cover, and relied strongly on semi‐extensive grasslands covering at least 30% of the surface within 300 m of the territory centre and with high orthopteran availability near the centre (50‐m radius), revealing a need for good foraging grounds near the nest. At a larger spatial scale within a radius of 1000 m, the habitat suitability of Scops Owls was negatively related to forest cover. The resulting ESM predictions provide valuable tools for conservation planning, highlighting sites in need of particular conservation efforts together with offering estimates of the percentage of habitat types and necessary prey abundance that could be used as targets in future management plans to ensure the persistence of the population.
Understanding the evolutionary forces maintaining avian color polymorphisms is a major challenge in evolutionary ecology. Aiming to give new insights into the functional basis of color polymorphism, ...we studied plumage color variation and its associations with fitness proxies in an individually marked population of scops owls Otus scops during 8 yr. We found a repeatable method to assign individuals to three discrete morphs, using both photography and spectrophotometry. Individuals were either grey (33%), intermediate (37%) or brown (30%). Scops owl proved to be polymorphic as the three morphs were found in the two sexes and across ages. Frequency distribution of color within the population did not vary for the two sexes during the study period, and, within individuals, color was repeatable and not explained by plumage maturation. Females of the two extreme morphs seemed to mate at random while intermediate females seemed to mate assortatively. The color of females was not related to laying date, mean fledging mass or number of fledglings per nest. Finally, intermediate females survived slightly better than females of the other morphs. Hence, pairing seems to favor intermediate males, because all females include intermediate males among their mates, and survival seems to favor intermediate females. Despite this, the proportion of intermediate individuals did not increase during the study. This fact may allude to the importance, not analysed here, of larger scale temporal and/or spatial fluctuations in selection acting on different fitness‐affecting factors, which may help to explain the maintenance of color polymorphism in the species.
•The Scops Owl population is declining.•Main causes are linked to human activity.•Landscape dynamics reveal its potential fate.•Spatial results serve as decision support for proper environmental ...planning.
Biodiversity is declining across Europe. Modern agricultural practices, habitat fragmentation, land abandonment and climate change are key factors causing current trends in environmental change. Mobile organisms such as raptors, positioned high in the food chain, are good indicators of negative or positive landscape dynamics, since their response is fast. This assumption was tested by investigating the Scops Owl (Otus scops) population in a traditional Central European cultural landscape (Goričko Nature Park GNP) in Slovenia. The negative trend in male calling Scops Owls was correlated with static and dynamic environmental change variables derived from remotely sensed or field-based, multi-temporal data sources. Key geospatial predictors were identified and used for bird calling and breeding (C&B) suitability modelling. All geospatial models developed predicted a decline in C&B suitability (even by 33%) in almost all areas where the bird is currently active. However, the NE part of the GNP could achieve better C&B conditions for theScops Owl in the coming years (a potential 36% increase in suitability). Predictions indicate that more effort and action, to conserve the Scops Owl in the study area should be implemented in the N, NE and E part of the hilly GNP. Our results are thus highly applicable not just for decision makers in this protected area but rather in all areas across the Scops Owl’s continental population, since the methodology is easily replicable and transferable.
Farmland birds in the European Union have declined by 57% in the past 35 years, raising the need for efficient, large-scale conservation measures to halt and reverse their negative trends. The ...Eurasian Scops Owl Otus scops is an indicator of extensively managed agricultural landscapes, typical of areas of high biodiversity. Its breeding biology is poorly known, but central to understanding the drivers of its marked decline in different European countries, including Slovenia. We used GPS-loggers to study home range size and habitat use of breeding individuals in NE Slovenia. Kernel home ranges (95%) of three females were estimated and their habitat use was analysed by spatial logistic regression models with Moran's Eigenvectors. Individual home range sizes ranged from 2.2 to 48.2 ha. In general, the females preferred to forage close to their nests. One female had a much larger home range than the other two, because of her exploitation of presumably highly profitable foraging grounds far away from her nest. In a mosaic of different agricultural habitats, the females showed a clear preference for extensively managed areas, such as hedges, meadows, abandoned vineyards and traditional orchards. Based on our findings several conservation measures are proposed, aimed at enhancing insect diversity and abundance as well as prey accessibility.
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