Iñigo Zuberogoitia

Habitat preferences for Long-eared Owls Asio otus and Little Owls Athene noctua in semi-arid environments at three spatial scales

Capsule There is a relationship between owl numbers and the availability of the agri-forest patchwork. Aims To model habitat preferences at three different scales of two predators largely neglected within the framework of Environmental Impact Assessment (EIA) studies. Methods We studied habitat preferences of Long-eared Owls and Little Owls by comparing habitat composition around 28 and 78 occupied territories respectively with 55 non-occupied territories in Alicante (eastern Spain). Generalized linear models were used to examine patterns of habitat preference at three different spatial scales: nest-site, home range and landscape. Results At the nest-site scale, Long-eared Owls preferred wooded areas with few paved roads while Little Owls preferred arid plantations. Furthermore, the probability of finding an occupied territory increased with the proximity of another occupied territory in the surroundings. The home range scale models mirror the feeding requirements of the owls. Thus, Long-eared Owls occupied areas with high percentages of forest, arid plantations, edges between these two land uses, short distances between nests, with presence of conspecifics and little human disturbance. Little Owls occupied arid plantations with high availability of linear structures and the proximity of villages. At the landscape scale, Long-eared Owls eluded extensive forests, and Little Owls preferred arid plantations. Conclusions We suggest a hierarchical process of habitat selection for both owls regarding fitting trophic resources at the broadest scales and adequate sites for breeding and roosting at the smallest scale. EIA studies must consider that protecting small areas around single nests may not be an efficient conservation option compared with preserving clusters of territories for both species.

Roles of raptors in a changing world: from flagships to providers of key ecosystem services

Summary. Birds of prey have been, in comparison to other avian groups, an uncommon study model, mainly due to the limitations imposed by their conservative life strategy (low population density and turnover). Nonetheless, they have attracted a strong interest from the point of view of conservation biology because many populations have been close to extinction and because of their recognised role in ecosystems as top predators and scavengers and as flagship species. Today, after more than a century of persecution, and with the exception of some vultures still very much affected by illegal poisoning, many populations of birds of prey have experienced significant recoveries in many regions of Spain and the European Mediterranean. These changes pose new challenges when addressing the conservation of raptors in the coming decades. On this basis, and from a preferentially Mediterranean perspective, we have focused our attention on the need of describing and quantifying the role of these birds as providers of both regulating (rodent pest control and removal of livestock carcasses) and cultural ecosystem services. Moreover, we revisited persisting conflicts with human interests (predation of game species) and call attention to the emergence of new conflicts with a strong social and media component such as the predation on live cattle by vultures. Also, the rampant humanization of the environment determines the need for new solutions to the growing, yet scarcely explored, problem of accidents in new infrastructures such as mortality in wind farms. Finally, we explored in depth the ecological response of birds of prey to large-scale habitat changes such as urbanisation and abandonment of marginal lands that are also expected to increase in the near future. We urgently need more scientific knowledge to provide adequate responses to the challenge of keeping healthy populations of avian predators and scavengers in a rapidly changing world.

Landscape features in the habitat selection of European mink ( Mustela lutreola ) in south-western Europe

Habitat change is one of the main factors influencing the decline of the western population of European mink Mustela lutreola, but data on habitat selection are scarce. Landscape features influencing selection of habitat and resting sites of male European mink were studied using radio-tracking. None of the habitat descriptors accounted for the habitat selection of European mink during their activity periods. On the other hand, resting site selection was correlated with the presence of bramble patches. Intensive use of bramble patches is explained as a consequence of the need of mink for protection against predators. Moreover, the high availability of bramble patches provides the mink with easy resting sites.

How to manage human-induced mortality in the Eagle Owl Bubo bubo

Summary The Eagle Owl Bubo bubo, which feeds mainly on rabbits and partridges, has been persecuted widely for causing damage to game interests. Although it is a protected species throughout Europe, there is a noteworthy gap in the scientific literature on the causes of mortality in this top predator. Here, we assess the relative importance and the geographical and temporal variation of human-related causes of death by reviewing 1,576 files of individuals admitted to wildlife rescue centres in Spain, a stronghold for Eagle Owls. The main known cause of death was interaction with powerlines followed by persecution and collisions with game fences and cars. There were within-year variations in the distribution of persecution, electrocution and collisions with game fences. Some man-induced causes of mortality were seen to depend on both the geographical region and the period of the year; moreover, mortality within each region was also yeardependent. Since there are strong socio-economic and ethical components involved, management guidelines are discussed bearing in mind such points of view.

The response of the Eagle Owl (Bubo bubo) to an outbreak of the rabbit haemorrhagic disease@@@Die Reaktion des Uhus (Bubo bubo) auf einen Ausbruch der hämorraghischen Krankheit bei Kaninchen (Oryctolagus cuniculus)

The Eagle Owl (Bubo bubo) is a generalist predator that in Mediterranean areas feeds mainly on Rabbits (Oryctolagus cuniculus) At the end of 1997, a local outbreak of the rabbit haemorrhagic disease (RHD) decimated Rabbit populations in the area of Alicante (eastern Spain) so that Rabbit numbers in 1998 crashed to almost nil. Prior to the outbreak we had found 19 occupied Eagle Owl territories, and the owls had been feeding mainly on Rabbits. After the RHD epidemic, we found only six occupied territories and the owls were still feeding mainly on Rabbits. Diet composition was very similar between the periods, indicating that the owls did not diversify their diet in response to main prey scarcity. No significant differences in the proportion of Rabbit in the diet were found between the periods, suggesting that the impact of predation on Rabbits may be independent of the density of Rabbit populations (type I functional response). This response is not typically associated with generalist predators. In the territories that were still occupied after the outbreaks, the owls took substantial numbers of Hedgehogs (Erinaceus europaeus) and Red-legged Partridges (Alectoris rufa). Rats (Rattus spp), a common alternative prey, were not taken in the study area. Six breeding attempts were recorded before the RHD, and none after the RHD. This leads a to believe that only the combination of Hedgehog and Red-legged Partridge availability with the readier availability of sick Rabbits allowed a small population of owls to survive in the area, but did not allowed breeding. The predator-prey system formed by Eagle Owls and Rabbits in Mediterranean regions is more fragile than previously thought. Der Uhu (Bubo bubo) ist ein wenig spezialisierter Greifvogel, der sich im Mittelmeerraum hauptsächlich von Kaninchen ernährt. Ende 1997 wurde die Kaninchenpopulation im Gebiet von Alicante (Ostspanien) durch einen Ausbruch der hämorrhagischen Krankheit (RHD) so stark dezimiert, dass der Kaninchenbestand 1998 nahezu zusammengebrochen war. Vor dem Ausbruch der Krankheit waren 19 Uhu-Reviere besetzt, und die Uhus lebten hauptsächlich von Kaninchen. Nach dem RHD-Ausbruch zählten wir nur noch sechs besetzte Reviere; die Uhus ernährten sich aber immer noch hauptsächlich von Kaninchen. Die Zusammensetzung der Nahrung war in beiden Perioden sehr ähnlich, was darauf hinweist, dass Uhus ihr Beutespektrum nicht erweitern, wenn ihr hauptsächliches Beutetier knapp wird. Dies legt nahe, dass die Anzahl geschlagener Kaninchen unabhängig von deren Populationsdichte ist (Typ I funktionelle Reaktion). Diese Reaktion ist untypisch für nicht spezialisierte Greifvögel. In den Revieren, die nach dem Ausbruch der Seuche noch bewohnt waren, fraßen die Uhus eine beträchtliche Anzahl Igel (Erinaceus europaeus) und Rebhühner (Alectoris rufa). Auf gewöhnliche alternative Beutetiere wie Ratten (Rattus spp) wurde im untersuchten Gebiet nicht zurückgegriffen. Sechs Brutversuche waren vor dem RHD-Ausbruch verzeichnet worden, danach kein einziger. Demzufolge lässt sich vermuten, dass nur der vereinte Effekt eines Igel- und Rebhuhnvorrats und darüber hinaus ein größeres Vorhandenseins kranker Kaninchen einer kleinen Anzahl der Uhus das Überleben in dem Gebiet ermöglichte, das Brüten jedoch nicht zuließ. Das im Mittelmeergebiet aus Uhu und Kaninchen bestehende Raubtier-Opfer-System ist anfälliger als bisher angenommen wurde.

Individual Quality Explains Variation in Reproductive Success Better than Territory Quality in a Long-Lived Territorial Raptor

Evolution by natural selection depends on the relationship between individual traits and fitness. Variation in individual fitness can result from habitat (territory) quality and individual variation. Individual quality and specialization can have a deep impact on fitness, yet in most studies on territorial species the quality of territory and individuals are confused. We aimed to determine if variation in breeding success is better explained by territories, individual quality or a combination of both. We analysed the number of fledglings and the breeding quality index (the difference between the number of fledglings of an individual/breeding pair and the average number of fledglings of the monitored territories in the same year) as part of a long term (16 years) peregrine falcon (Falco peregrinus) monitoring program with identification of individuals. Using individual and territory identities as correlates of quality, we built Generalised Linear Models with Mixed effects, in which random factors depicted different hypotheses for sources of variation (territory/individual quality) in the reproductive success of unique breeding pairs, males and females, and assessed their performance. Most evidence supported the hypothesis that variation in breeding success is explained by individual identity, particularly male identity, rather than territory. There is also some evidence for inter year variations in the breeding success of females and a territory effect in the case of males. We argue that, in territorial species, individual quality is a major source of variation in breeding success, often masked by territory. Future ecological and conservation studies on habitat use should consider and include the effect of individuals, in order to avoid misleading results.

Home ranges of European minkMustela lutreola in southwestern Europe

We radiotracked 7 European minkMustela lutreola Linnaeus, 1761 (5 males and 2 females), to determine their distribution, size and temporal changes of their home range in an area of southwestern Europe, where American minkM. vison was not established. Size of home ranges varied from 11 to 17 km along watercourses in males and were 0.6 and 3.6 km in females. Home ranges of males were larger than those found in previous studies. Most females captured (either radiotracked or not) were found within the home range of males. Males occupied adjoining river sections with minimal range overlap, suggesting an intrasexually exclusive spacing pattern for males. Each month males used new river stretches, mainly along tributaries; meanwhile they showed a steady use of their stem river section. Resting sites were mainly beneath dense brambles ofRubus patches located in the river bank.

Estimating costs and outcomes of invasive American mink (Neovison vison) management in continental areas: a framework for evidence based control and eradication

Introduced predators are a major threat to biodiversity. While in island ecosystems the favoured management option is species eradication, in continental areas most managers tend to control-orientated options, assuming that eradication is an impossible goal. However, many management actions are conducted without precise or quantifiable goals, and their output is difficult to assess due to the lack of experimental approaches and scientific evidence. Here, we analyse the results of a typical small-scale short-term management action consisting of live-trapping and culling invasive American mink. We estimate the American mink population size at the beginning of the study assuming three different scenarios, assess the output of the management action in each scenario and model the results of further trapping efforts. Based on the results we estimate the effort and economic costs required for culling different population percentages per unit area, as well as the costs and feasibility of eradication. Our results provide a basis for planning invasive predator management, setting realistic management goals and estimating funding required, as well as a framework for managers to evaluate on-going management actions. In addition, our results suggest that American mink eradication from some continental areas would be feasible with current techniques at a moderate-low cost. We suggest that invasive predator management in continental areas should move towards eradication when feasible, regarding control as a second option.

Site and landscape features ruling the habitat use and occupancy of the polecat (Mustela putorius) in a low density area: a multiscale approach

We studied the habitat of the polecat at different scales in a low density area. For this purpose we gathered data on the presence of the species and characterised them by location, home range and landscape scales. Polecats selected areas of high diversity close to, but not in, streams whilst avoiding intensively managed conifer plantations and dense urban areas. Variables determining the presence/absence of the species were found at home range scales, which implies that management and conservation practices for the species should be aimed mainly at this scale. Finally, our results agree with previously published works, which validate GIS-based approaches as a tool for carnivore management in areas with scarce data or in cases of rare species.

Social Interactions between Two Owl Species Sometimes Associated with Intraguild Predation

Species may act simultaneously as competitor and predator for other species at the same trophic level. This is known as Intraguild Predation (IGP). Most research on this topic describes the final steps of this phenomenon, when one species suffers lost progeny or decreased numbers due to predation and competition by another species. However, little is known about the mechanism that regulates this interaction in previous steps. In this work two species of the same guild (Little Owl Athene noctua and Barn Owl Tyto alba) were selected to test the hypothesis that the hunting and social behaviour of the Little Owl would be conditioned by the presence of Barn Owls. Nine Little Owls were radio-tracked and monitored for nine months. 1223 fixes were obtained and 250 hours of listening were recorded. Moreover, during this time Barn Owls were detected 66 times screeching, hunting or flying in the same areas as the monitored Little Owls. The subsequent activity (movements and voices) of tagged and untagged Little Owls was observed during 30-minute periods. The results show that Little Owl behaviour was affected by Barn Owl presence. When Little Owls noted the presence of Barn Owls, they stayed quiet and silent, or alternatively, sought refuge in the branches of trees or in secure holes in buildings, resuming their activities minutes later, when the risk of predation was presumably lower. This behaviour may have enabled survival and successful breeding of Little Owl in close proximity to Barn Owls.