Jabi Zabala

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.

Winter habitat preferences of feral American mink Mustela vison in Biscay, Northern Iberian Peninsula

We studied correlates of habitat use of riparian feral American minkMustela vison Schreber, 1777 during winter in Biscay (Northern Iberian Peninsula). We live-trapped and radio-tagged 10 American mink (5 males and 5 females) and successfully radiotracked 7 of them (3 males and 4 females). During resting periods both sexes selected areas with dense scrub and near to deep waters. Both sexes used underground dens as well as resting sites located above the ground, but during cold days females rested in buildings much more often than males. Active females used areas of dense scrub, and males used large scrub patches. The results are interpreted in the light of mink hunting techniques and perceived predation risk: on larger scales, mink select areas primarily by food abundance, while on very small scales they use scrub and similar structures providing safe areas to hunt, forage and rest. The strong preference for banks with dense scrub provides options for management of the species.

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.

Seasonal Blowfly Distribution and Abundance in Fragmented Landscapes. Is It Useful in Forensic Inference about Where a Corpse Has Been Decaying

Blowflies are insects of forensic interest as they may indicate characteristics of the environment where a body has been laying prior to the discovery. In order to estimate changes in community related to landscape and to assess if blowfly species can be used as indicators of the landscape where a corpse has been decaying, we studied the blowfly community and how it is affected by landscape in a 7,000 km2 region during a whole year. Using baited traps deployed monthly we collected 28,507 individuals of 10 calliphorid species, 7 of them well represented and distributed in the study area. Multiple Analysis of Variance found changes in abundance between seasons in the 7 analyzed species, and changes related to land use in 4 of them (Calliphora vomitoria, Lucilia ampullacea, L. caesar and L. illustris). Generalised Linear Model analyses of abundance of these species compared with landscape descriptors at different scales found only a clear significant relationship between summer abundance of C. vomitoria and distance to urban areas and degree of urbanisation. This relationship explained more deviance when considering the landscape composition at larger geographical scales (up to 2,500 m around sampling site). For the other species, no clear relationship between land uses and abundance was found, and therefore observed changes in their abundance patterns could be the result of other variables, probably small changes in temperature. Our results suggest that blowfly community composition cannot be used to infer in what kind of landscape a corpse has decayed, at least in highly fragmented habitats, the only exception being the summer abundance of C. vomitoria.

The Dho-gaza and Mist Net with Eurasian Eagle-Owl (Bubo bubo) Lure: Effectiveness in Capturing Thirteen Species of European Raptors

EL USO DE DHO-GAZA Y REDES CON BUBO BUBO COMO SEÑUELO: EFICACIA EN LA CAPTURA DE 13 ESPECIES DE RAPACES EUROPEAS La captura de aves rapaces resulta fundamental para el desarrollo de proyectos de investigación, aunque no siempre resulta una tarea fácil. Durante seis años (entre abril de 2000 y agosto de 2006) realizamos diferentes pruebas para capturar aves rapaces en dos zonas de España, Bizkaia y Murcia. Como señuelo se utilizaron búhos improntados de la especie Bubo bubo, procedentes de centros de recuperación, que eran colocados cerca de las redes en las proximidades de nidos activos de aves rapaces. Durante los seis años realizamos 190 intentos durante el periodo reproductivo y 36 intentos durante el periodo no reproductivo. El éxito de captura fue del 58.8%, capturándose 60 machos y 73 hembras de 10 especies. Las rapaces forestales fueron las más fáciles de capturar, principalmente las de la especie Buteo buteo. No obstante, Falco tinnunculus fue la especie más propensa a ser capturada con este método. Las especies Falco peregrinus y Falco subbuteo fueron capturadas en escasas ocasiones debido al ocasional comportamiento de impasibilidad hacia el búho.

Sexing, ageing and moult of Buzzards Buteo buteo in a southern European area

In order to obtain a reliable method for sexing and ageing Buzzards Buteo buteo breeding in southern Europe, 115 birds from a wildlife rehabilitation centre and 43 trapped birds were measured, sexed and aged over four years (2000–2003). Dead birds were sexed by examining their gonads, and live birds by the presence of a brood patch. Wing length, minimum tarsus width and body weight were the only variables which differed significantly between the sexes, although there was much overlap for the wing length and weight. Buzzards with less than 7 mm minimum tarsus width were male and those greater than 7.9 mm were female. Birds did not complete moult in one year, moulting less than 60% of the flight feathers in one season. The first and the second moult followed a pattern, but afterwards moult was unpredictable and totally asymmetric. Also, half the females and 33% of males had started to moult within 30 days of their chicks hatching. These results differ from those published for Buzzards from northern Europe. The size and moult pattern depend on factors such as prey availability and migratory status, which in turn vary between areas. We therefore suggest caution when considering the moult strategies, ageing criteria and sexing criteria published for other countries.