Bias in little owl population estimates using playback techniques during surveys

Problemas en las estimas poblacionales de mochuelos cuando se realizan censos con reclamos Se desarrollaron dos estudios diferentes para probar la eficiencia de los censos por medio de reclamos de mochuelos (Athene noctua): (1) un seguimiento intensivo de las respuestas a los reclamos de mochuelos radio–marcados en una pequeña área, (2) un estudio extensivo utilizando reclamos para estimar la eficiencia del método como herramienta para detectar la presencia de mochuelos. En el primer caso, se detectaron 8,12 mochuelos de media en un periodo de censo de 30′, número cercano al tamaño de población real; además, se detectaron esplazamientos significativos de los mochuelos desde la posición inicial (antes de conectar el reclamo) a las posiciones siguientes durante la ejecución del reclamo. Sin embargo, tan sólo se detectó una media de 2,25 y 5,37 mochuelos en los primeros 5′ y 10′ respectivamente. En el segundo caso, se detectaron 137 territorios de mochuelos en 105 unidades de muestreo positivas. La tasa de ocupación fue de 0,35, la ocupación estimada de 0,393 y la probabilidad de detección de 0,439. La probabilidad acumulada estimada de detección sugiere que se precisarían de al menos cuatro muestreos en un estudio extensivo si se pretende detectar el 95% de las áreas ocupadas por mochuelos. Palabras clave: Mochuelo común, Métodos de censo, Programa Presence, Eficacia de detección, Actividad vocal.To test the efficiency of playback methods to survey little owl (Athene noctua) populations we carried out two studies: (1) we recorded the replies of radio–tagged little owls to calls in a small area; (2) we recorded call broadcasts to estimate the effectiveness of the method to detect the presence of little owl. In the first study, we detected an average of 8.12 owls in the 30' survey period, a number that is close to the real population; we also detected significant little owl movements from the initial location (before the playback) to the next locations during the survey eriod. However, we only detected an average of 2.25 and 5.37 little owls in the first 5' and 10', respectively, of the survey time. In the second study, we detected 137 little owl territories in 105 positive sample units. The occupation rate was 0.35, the estimated occupancy was 0.393, and the probability of detection was 0.439. The estimated cumulative probability of detection suggests that a minimum of four sampling times would be needed in an extensive survey to detect 95% of the areas occupied by little owls. Key words: Little owl, Survey methods, Presence Program, Detection efficiency, Vocal activity.Problemas en las estimas poblacionales de mochuelos cuando se realizan censos con reclamos Se desarrollaron dos estudios diferentes para probar la eficiencia de los censos por medio de reclamos de mochuelos (Athene noctua): (1) un seguimiento intensivo de las respuestas a los reclamos de mochuelos radio–marcados en una pequeña área, (2) un estudio extensivo utilizando reclamos para estimar la eficiencia del método como herramienta para detectar la presencia de mochuelos. En el primer caso, se detectaron 8,12 mochuelos de media en un periodo de censo de 30′, número cercano al tamaño de población real; además, se detectaron esplazamientos significativos de los mochuelos desde la posición inicial (antes de conectar el reclamo) a las posiciones siguientes durante la ejecución del reclamo. Sin embargo, tan sólo se detectó una media de 2,25 y 5,37 mochuelos en los primeros 5′ y 10′ respectivamente. En el segundo caso, se detectaron 137 territorios de mochuelos en 105 unidades de muestreo positivas. La tasa de ocupación fue de 0,35, la ocupación estimada de 0,393 y la probabilidad de detección de 0,439. La probabilidad acumulada estimada de detección sugiere que se precisarían de al menos cuatro muestreos en un estudio extensivo si se pretende detectar el 95% de las áreas ocupadas por mochuelos. Palabras clave: Mochuelo común, Métodos de censo, Programa Presence, Eficacia de detección, Actividad vocal

The Fifth International Little Owl Symposium, 4–6 February 2011, Vic, Catalonia (Spain)

The First International Little Owl Symposium took place in Champ–sur–Marne (France) in November 2000, organized by the International little owl Working Group (ILOWG). It was the first international meeting regarding a sole owl species in Europe. Since then, efforts have been made to improve our knowledge and develop management plans for little owl conservation, and every new advance has been shared among all of us, owl researchers and owl friends, at regular international meetings. The Fifth Symposium gave continuity to the series of previous meetings held in France, England and Belgium. The most recent meeting was held in Herzele, Flanders, and the highlight was the presentation of the latest little owl monograph of Van Nieuwenhuyse et al., 2008. This meeting demonstrated the need to promote future gatherings of researchers.The First International Little Owl Symposium took place in Champ–sur–Marne (France) in November 2000, organized by the International little owl Working Group (ILOWG). It was the first international meeting regarding a sole owl species in Europe. Since then, efforts have been made to improve our knowledge and develop management plans for little owl conservation, and every new advance has been shared among all of us, owl researchers and owl friends, at regular international meetings. The Fifth Symposium gave continuity to the series of previous meetings held in France, England and Belgium. The most recent meeting was held in Herzele, Flanders, and the highlight was the presentation of the latest little owl monograph of Van Nieuwenhuyse et al., 2008. This meeting demonstrated the need to promote future gatherings of researchers.The First International Little Owl Symposium took place in Champ–sur–Marne (France) in November 2000, organized by the International little owl Working Group (ILOWG). It was the first international meeting regarding a sole owl species in Europe. Since then, efforts have been made to improve our knowledge and develop management plans for little owl conservation, and every new advance has been shared among all of us, owl researchers and owl friends, at regular international meetings. The Fifth Symposium gave continuity to the series of previous meetings held in France, England and Belgium. The most recent meeting was held in Herzele, Flanders, and the highlight was the presentation of the latest little owl monograph of Van Nieuwenhuyse et al., 2008. This meeting demonstrated the need to promote future gatherings of researchers

Status of carnivores in Biscay (N lberian peninsula)

The first study on the carnivore community of Biscay was published in 1985. The present study, made twelve years later, was carried out to assess the present situation of these mammals. In this work, data collected from 1990 to 1996 by trapping, sighting, and surveying road and other kills, as well as faeces and tracks are reported. Records of 12 species were obtained, of which American mink Mustela vison (Schreber, 1777) is cited for the first time, and the wolf reappears as a non-occasional species. The main trends observed during the last twelve years seem to be related to changes in land use and management of natural resources. The situation has turned favourable for the most opportunistic species, which have become very abundant in some areas, while populations of the most specialist or relictic species show a more restricted distribution. At the same time, the expansion of wolf and European mink, with the appearance of American mink for the first time, reflect a dynamic but very unstable scene. Key words: Carnivores, Population status, Distribution, Conservation, lberian peninsula.The first study on the carnivore community of Biscay was published in 1985. The present study, made twelve years later, was carried out to assess the present situation of these mammals. In this work, data collected from 1990 to 1996 by trapping, sighting, and surveying road and other kills, as well as faeces and tracks are reported. Records of 12 species were obtained, of which American mink Mustela vison (Schreber, 1777) is cited for the first time, and the wolf reappears as a non-occasional species. The main trends observed during the last twelve years seem to be related to changes in land use and management of natural resources. The situation has turned favourable for the most opportunistic species, which have become very abundant in some areas, while populations of the most specialist or relictic species show a more restricted distribution. At the same time, the expansion of wolf and European mink, with the appearance of American mink for the first time, reflect a dynamic but very unstable scene. Key words: Carnivores, Population status, Distribution, Conservation, lberian peninsula.The first study on the carnivore community of Biscay was published in 1985. The present study, made twelve years later, was carried out to assess the present situation of these mammals. In this work, data collected from 1990 to 1996 by trapping, sighting, and surveying road and other kills, as well as faeces and tracks are reported. Records of 12 species were obtained, of which American mink Mustela vison (Schreber, 1777) is cited for the first time, and the wolf reappears as a non-occasional species. The main trends observed during the last twelve years seem to be related to changes in land use and management of natural resources. The situation has turned favourable for the most opportunistic species, which have become very abundant in some areas, while populations of the most specialist or relictic species show a more restricted distribution. At the same time, the expansion of wolf and European mink, with the appearance of American mink for the first time, reflect a dynamic but very unstable scene. Key words: Carnivores, Population status, Distribution, Conservation, lberian peninsula

The flight feather moult pattern of the bearded vulture (Gypaetus barbatus).

Moult is an extremely time-consuming and energy-demanding task for large birds. In addition, there is a trade-off between the time devoted to moulting and that invested in other activities such as breeding and/or territory exploration. Moreover, it takes a long time to grow a long feather in large birds, and large birds that need to fly while moulting cannot tolerate large gaps in the wing, but only one or two simultaneously growing feathers. As a consequence, large birds take several years to complete a full moult cycle, and they resume the moult process during suboptimal conditions. A clear example of this pattern is the Bearded Vulture (Gypaetus barbatus), which needs 2-3 years for changing all flight feathers. Here we describe the sequence, extent, and timing of moult of 124 Bearded Vultures in detail for the first time. We found that extent and timing of flight feather moult was different between age classes. Subadults (from 3rd to 5th calendar year) started moult, on average, in early March, whereas adults only started moult, on average, in late April, possibly due to breeding requirements. Second calendar year individuals delayed onset of moult until the middle of May. In general, the moult lasted until November, and although adults started to moult later than subadults, they moulted more feathers. Subadults needed 3 years for moulting all flight feathers, whereas adults normally completed it in 2 years

Bird collisions in a railway crossing a wetland of international importance (Sado estuary, Portugal)

L. Borda-de-Água et al. (eds.), Railway Ecology, chapter 7, p. 103-115Many studies have evaluated bird mortality in relation to roads and other human structures, but little is known about the potential impacts of railways. In particular, it is uncertain whether railways are an important mortality source when crossing wetlands heavily used by aquatic birds. Here we analyze bird collisions in a railway that crosses the Nature Reserve of the Sado Estuary (Portugal) over an annual cycle, documenting bird mortality and the flight behaviour of aquatic birds in relation to a bowstring bridge. During monthly surveys conducted on 16.3 km of railway, we found 5.8 dead birds/km/10 survey days in the section crossing wetland habitats (6.3 km), while <0.5 dead birds/km/10 survey days were found in two sections crossing only forested habitats. Most birds recorded were small songbirds (Passeriformes), while there was only a small number of aquatic birds (common moorhen, mallard, flamingo, great cormorant, gulls) and other non-passerines associated with wetlands (white stork). During nearly 400 h of observations, we recorded 27,000 movements of aquatic birds across the Sado bridge, particularly in autumn and winter. However, only <1% of movements were within the area of collision risk with trains, while about 91% were above the collision risk area, and 8% were below the bridge. Overall, our case study suggests that bird collisions may be far more numerous in railways crossing wetland habitats than elsewhere, although the risk to aquatic birds may be relatively low. Information from additional study systems would be required to evaluate whether our conclusions apply to other wetlands and railway linesinfo:eu-repo/semantics/publishedVersio

The compensatory potential of increased immigration following intensive American mink population control is diluted by male-biased dispersal

Attempts to mitigate the impact of invasive species on native ecosystems increasingly target large land masses where control, rather than eradication, is the management objective. Depressing numbers of invasive species to a level where their impact on native biodiversity is tolerable requires overcoming the impact of compensatory immigration from non-controlled portions of the landscape. Because of the expected scale-dependency of dispersal, the overall size of invasive species management areas relative to the dispersal ability of the controlled species will determine the size of any effectively conserved core area unaffected by immigration from surrounding areas. However, when dispersal is male-biased, as in many mammalian invasive carnivores, males may be overrepresented amongst immigrants, reducing the potential growth rate of invasive species populations in re-invaded areas. Using data collected from a project that gradually imposed spatially comprehensive control on invasive American mink (Neovison vison) over a 10,000 km2 area of NE Scotland, we show that mink captures were reduced to almost zero in 3 years, whilst there was a threefold increase in the proportion of male immigrants. Dispersal was often long distance and linking adjacent river catchments, asymptoting at 38 and 31 km for males and females respectively. Breeding and dispersal were spatially heterogeneous, with 40 % of river sections accounting for most captures of juvenile (85 %), adult female (65 %) and immigrant (57 %) mink. Concentrating control effort on such areas, so as to turn them into “attractive dispersal sinks” could make a disproportionate contribution to the management of recurrent re-invasion of mainland invasive species management areas

Interspecific Hybridization Increased in Congeneric Flatfishes after the Prestige Oil Spill

Marine species with relatively low migratory capacity are threatened by habitat alterations derived from human activities. In November 2002 the tanker Prestige sank off the Spanish northwest coast releasing 70,000 tons of fuel and damaging biota in the area. Despite efforts to clean the damaged areas, fuel remnants have affected marine species over the last nine years. This study is focused on two flatfish, Lepidorhombus boscii (four-spotted megrim) and L. whiffiagonis (megrim), whose spawning areas are located at the edge of the continental platform. We have analyzed megrim samples from North Spanish and French waters obtained before and after the oil spill. Genotypes at the nuclear marker 5S rDNA indicate a significant increase in interspecific hybridization after the Prestige accident, likely due to forced spawning overlap. The mitochondrial D-Loop region was employed for determining the direction of hybrid crosses, which were most frequently L. boscii female x L. whiffiagonis male. Reduced ability of L. boscii females to select conspecific mates would explain such asymmetric hybridization. To our knowledge this is the first time that increased hybridization between fish species can be associated to an oil spill. These results illustrate the potential long-term effect of petrol wastes on wild fish species

Developmental Exposure to a Toxic Spill Compromises Long-Term Reproductive Performance in a Wild, Long-Lived Bird: The White Stork (Ciconia ciconia)

Background/Objective: Exposure to environmental contaminants may result in reduced reproductive success and long- lasting population declines in vertebrates. Emerging data from laboratory studies on model species suggest that certain life- stages, such as development, should be of special concern. However, detailed investigations of long-term consequences of developmental exposure to environmental chemicals on breeding performance are currently lacking in wild populations of long-lived vertebrates. Here, we studied how the developmental exposure to a mine spill (Aznalco´ llar, SW Spain, April 1998) may affect fitness under natural conditions in a long-lived bird, the White Stork (Ciconia ciconia). Methodology: The reproductive performance of individually-banded storks that were or not developmentally exposed to the spill (i.e. hatched before or after the spill) was compared when these individuals were simultaneously breeding during the seven years after the spill occurred (1999–2005). Principal Findings: Female storks developmentally exposed to the spill experienced a premature breeding senescence compared with their non-developmentally exposed counterparts, doing so after departing from an unusually higher productivity in their early reproductive life (non-developmentally exposed females: 0.560.33SE fledglings/year at 3-yr old vs. 1.3860.31SE at 6–7 yr old; developmentally exposed females: 1.560.30SE fledglings/year at 3-yr old vs. 0.8660.25SE at 6– 7 yr old). Conclusions/Significance: Following life-history theory, we propose that costly sub-lethal effects reported in stork nestlings after low-level exposure to the spill-derived contaminants might play an important role in shaping this pattern of reproduction, with a clear potential impact on population dynamics. Overall, our study provides evidence that environmental disasters can have long-term, multigenerational consequences on wildlife, particularly when affecting developing individuals, and warns about the risk of widespread low-level contamination in realistic scenarios.Peer reviewe

Modelling the impact of toxic and disturbance stress on white-tailed eagle (Haliaeetus albicilla) populations

Several studies have related breeding success and survival of sea eagles to toxic or non-toxic stress separately. In the present investigation, we analysed single and combined impacts of both toxic and disturbance stress on populations of white-tailed eagle (Haliaeetus albicilla), using an analytical single-species model. Chemical and eco(toxico)logical data reported from laboratory and field studies were used to parameterise and validate the model. The model was applied to assess the impact of ∑PCB, DDE and disturbance stress on the white-tailed eagle population in The Netherlands. Disturbance stress was incorporated through a 1.6% reduction in survival and a 10–50% reduction in reproduction. ∑PCB contamination from 1950 up to 1987 was found to be too high to allow the return of white-tailed eagle as a breeding species in that period. ∑PCB and population trends simulated for 2006–2050 suggest that future population growth is still reduced. Disturbance stress resulted in a reduced population development. The combination of both toxic and disturbance stress varied from a slower population development to a catastrophical reduction in population size, where the main cause was attributed to the reduction in reproduction of 50%. Application of the model was restricted by the current lack of quantitative dose–response relationships between non-toxic stress and survival and reproduction. Nevertheless, the model provides a first step towards integrating and quantifying the impacts of multiple stressors on white-tailed eagle populations