Standing out from the crowd: are patagial wing tags a potential predator attraction for harriers (Circus spp.)?

et al.Wing tags have been used on many bird species to facilitate individual recognition, although tags are not only conspicuous for humans but may also attract the attention of potential predators. During a Peregrine Falcon Falco peregrinus monitoring program (1997-2011) we collected prey remains from the nests of 37 Peregrine territories in the Basque Country, Northern Spain. We identified 3,127 prey items representing 132 bird species. In the 2009 breeding season, we found, for the first time, four Hen Harrier Circus cyaneus remains and the two wings with orange wing tags of a Montagu's Harrier Circus pygargus in one nest, 1 year later we found in the same nest eight Montagu's Harrier remains, one of them with wing tags, and in 2011 we found eight more Montagu's Harriers, one of them marked. Simultaneously, in the breeding season of 2010, the remains of another Montagu's Harrier were found in other Peregrine nest and two wings with orange and blue wing tags in the perch of a third pair. Our data thus shows an increase of predation rate of harriers by Peregrines; we discuss whether this could be related to the increasing use of wing tags in this species, and thus whether wing tags may have potential negative effects on the birds. We argue that further studies about the impact of identification techniques, and wing-tags in particular, on the survival of target species should be carried out.Peer Reviewe

Azor común – Accipiter gentilis (Linnaeus, 1758)

Aves - Orden Falconiformes - Familia Accipitridae en la Enciclopedia Virtual de Vertebrados Españoles, http://www.vertebradosibericos.org/.A comprehensive review of the natural history of the Northern Goshawk Accipiter gentilis in Spain.Peer reviewe

Halcón peregrino – Falco peregrinus Tunstall, 1771

Aves - Orden Falconiformes - Familia Falconidae en la Enciclopedia Virtual de Vertebrados Españoles, http://www.vertebradosibericos.org/. Versiones anteriores: 21-06-2005; 8-03-2007; 10-03-2008; 30-07-2012A comprehensive review of the natural history of the Peregrine falcon Falco peregrinus in Spain.Peer reviewe

Effect of nest composition, experience and nest quality on nest-building behaviour in the Bonelli's Eagle.

In bi-parentally built nests, there is evidence to suggest that nests are extended phenotypic signals that accurately indicate the quality of the building parent/s. Raptors often use a variety of materials to build their nests (natural, such as branches, but also non-natural objects), presumably due to their insulating properties, their suitability to advertise occupancy of the nest, and to decrease pathogen and parasite loads. However, in raptors where both sexes collaborate in nest construction, it is unclear whether nest building (taking the amount of material carried to the nest as the potential predictor) is an indicator of parental quality, and whether the effort expended by both sexes could constitute an honest signal of parental quality to their partners. Between 2011 and 2016, we monitored 16 nests of Bonelli's Eagles (Aquila fasciata), and we examined data on sex, type of material brought to the nest, breeding experience, nest quality, timing, and nest-building investment prior to egg-laying from 32 identifiable Bonelli's Eagles during the pre-laying period to investigate the relative contribution of the sexes to the amount of nest material gathered. Our results indicate that sex is not a determining factor in nest-building effort, and that females did not increase their parental effort in response to the male's contribution, and supply of materials did not increase during the pre-laying period. In contrast, our models showed that: (1) the type of material supplied to the nest by both sexes varied significantly throughout the pre-laying period and (2) nest-building effort was determined by individual experience and nest quality. Therefore, our study suggests that male nest-building behaviour and investment by Bonelli's Eagles cannot be considered as an extended phenotypic signal. The differential use of hard and green material by both sexes in the early and late stages of nest-building period, and the fact that the more experienced individuals contributed a larger amount of material on low quality nests, are discussed in the contexts of signaling nest occupancy to conspecifics and competitors and the decrease of ectoparasite loads during the pre-laying period

Predictive models of habitat preferences for the Eurasian eagle owl Bubo bubo: A multiscale approach

Habitat preference of eagle owls Bubo bubo were examined through comparing habitat composition around 51 occupied cliffs and 36 non-occupied cliffs in Alicante (E Spain). We employed Generalized Linear Models to examine patterns of habitat preference at three different spatial scales: nest site (7 kim2), home range (25 km2), and landscape (100 km2). At the nest site scale, occupied cliffs were more rugged, had a greater proportion of forest surface in the surroundings, and were further from the nearest paved road than unoccupied cliffs. Additionally, probability of having an occupied cliff increased when there was another occupied territory in the surroundings. At both the home range scale and the landscape scale, high probabilities of presence of eagle owls were related to high percentages of Mediterranean scrubland around the cliffs, which are the preferred habitat of European rabbits Oryctolagus cuniculus, the main prey of the owls. We suggest a hierarchical process of habitat selection in the eagle owl concerning suitable trophic resources at the broadest scales and adequate sites for breeding and roosting at the smallest scale. However, it should be noted that some structural features such as the proximity of roads were not necessarily avoided by the owls, but their presence were possibly constrained by systematic killing of individuals. Our paper provides new evidence for the requirement of multi-scale approaches to gain insight into both the different limiting factors for the persistence of populations and the role of individual perception of the environment in the evolution of habitat selection.Peer Reviewe

Habitat preferences and causes of population decline for Barn Owls Tyto alba: A multi-scale approach

Aims: Habitat preferences of Barn Owls was studied in two areas of Spain undergoing large-scale habitat alteration. Location: Alicante (dry cultivations) and Valencia (irrigated cultivations) in eastern Spain. Methods: Habitat composition around occupied and unoccupied territories in dry cultures and irrigated cultures was compared (n = 71, 1989-2000). This study also described differences in habitat composition between occupied and deserted territories after major habitat alterations started in 1996. Generalized Linear Models were used to examine patterns of habitat preference at three different spatial scales: nest site, home range and landscape. Results: The study population declined by 69% in both study areas. At the nest site scale, Barn Owls preferred undisturbed areas with high availability of cavities, mainly in man-made structures. At the home range and landscape scales, Barn Owls occupied undisturbed areas with a high availability of cavities and high percentages of edges and ditches. Territory desertion was prompted by the modernisation or disappearance of man-made structures, depletion of edges and ditches, expansion of the road network and persecution. Accordingly, the spatial distribution of territories in irrigated cultures changed from uniform to random after habitat alteration. The availability of cavities alone does not account for all of the explained deviance, i.e., Barn Owls occupy structurally complex landscapes. Conclusions: Compensation measures for habitat loss such as nest-box programs, usually proposed within the framework of environmental impact assessment, are discouraged unless habitat restoration and effective control of persecution are promoted first.Peer reviewe

Population reinforcement of Eagle Owl Bubo bubo in Biscay (Spain)

Aims: The main objective of our study was to valorise the population reinforcement methods as a way to recover endangered species, the case of Eagle Owl Bubo bubo. Location: Biscay (Bizkaia), North of Spain. Methods: During five years we released Eagle Owls that came from wildlife rehabilitation centres located in other sites of Spain (Madrid, Cádiz, Huelva). All of them were individuals that had been treated in wildlife rehabilitation centres. These Owls were maintained in the Centro de Recuperación de la Fauna Silvestre de Biscay during nearly 45 days, where they improved the hunting techniques and the fly muscles. At the beginning, nine owls were radio-tracked and monitored and we compared two release methods: from a cage located in the release place or directly, resulting better the second method. Results: We released 64 Owls. Nineteen released Owls were found dead after 101 days, on average. They dispersed an average of 9.55 km. There was not correlation between the travelled distance and the time. We also located 10 Owls that had settled in territories. The average distance between the release point and them was 8.07 km. There were not differences between the distance travelled by the recovered Owls and the territorial Owls. Finally, we recorded three cases of reproduction. Conclusions: Thus and even, considering that more time is needed to find new evidences, we can consider this reinforcement program has been a success.Peer reviewe

Use of recorder calls for detecting long-eared owls Asio otus

Peer reviewe

Paíño europeo – Hydrobates pelagicus Linnaeus, 1758

Aves - Orden Procellariiformes - Familia Hydrobatidae en la Enciclopedia Virtual de Vertrebrados Españoles, http://www.vertebradosibericos.org/.A comprehensive review of the natural history of the Storm Petrel (Hydrobates pelagicus) in Spain.Peer reviewe

Reduced food availability induces behavioural changes in Griffon Vulture Gyps fulvus

In natural conditions, Griffon Vultures typically show shy behaviour and escape by flying if approached by humans. According to the state-dependent foraging theory, Griffon Vultures should modify their foraging behaviour depending on food availability and predation risk, humans being the main potential predator. We tested the Reaction Time (RT) and Flight Initiation Distance (FID) in five different artificial feeding schemes over three years in which food availability in the field varied significantly. The first scenario was set in a so-called “vulture restaurant”, in which government employees feed vultures that may exhibit tame behaviour and stay within a few meters from a feeding person. Scenario 2 involved similar conditions, but here the researchers not employees placed the food in the vulture restaurant. The vultures did not land at the restaurant until one day had passed, and they flew away when people approached them within 250 m. The third scenario was established in a local zoo several months after the closure of the vulture restaurant. Here, employees fed captive vultures that were often accompanied by wild birds that landed to take food. The RT was 14.2 min and the FID was 50 m. The fourth scenario was established during the subsequent breeding season in a mountain where vultures were fed by the authors of the present study. The RT was 2.8 min and the FID was 15.2 m. The fifth scenario was established in another mountain after the breeding season. Now, the RT was 19.2 min and the FID was 52.2 m. These results demonstrate the ability of vultures to evaluate the predation risk depending on food availability and their state of hunger, and their ability to modify their behaviour from “natural” caution (”shyness”) towards a more tolerant (”fearless”) behaviour.Peer reviewe