Estimación de los componentes de la varianza en los parámetros demográficos del cárabo común, Strix aluco

Survival rates of Tawny Owls (Strix aluco) were estimated using recapture and recovery data from approximately 20,000 nestling and adult owls ringed between 1980 and 1999 in southern Finland. Survival rates averaged 33% in the first year of life, 64% in the second, and 73% in subsequent years, but varied dramatically among years. Approximately 50% of annual variation in survival could be explained by stage of the vole cycle and severity of winter weather. Capture probabilities, an index of breeding propensity, varied dramatically among years, and could almost entirely be explained by the vole cycle, superimposed on a long–term increase in capture effort. Matrix models based on mean values in each year of the vole cycle, predict that in 2 out of 3 years, the population would decline by 13%–15% per year, offset by a large increase in the 3rd year. Numbers of nesting pairs are predicted to be low in one of three years, with no long–term trend, consistent with observed estimates of active nests.Se calcularon las tasas de supervivencia del cárabo común (Strix aluco) utilizando datos de recaptura y recuperación correspondientes a unos 20.000 cárabos comunes —entre polluelos y adultos—, anillados entre 1980 y 1999 en el sur de Finlandia. Las tasas de supervivencia alcanzaron un promedio del 33% en el primer año de vida, del 64% en el segundo y del 73% en los años subsiguientes, variando de forma espectacular entre los distintos años. Alrededor del 50% de la variación anual en la supervivencia pudo ser explicada por el estadio en que se encontraba el ciclo poblacional de los micrótidos y el rigor del clima invernal. Las probabilidades de captura —que representan un índice de la propensión a la reproducción—variaron considerablemente entre los distintos años, pudiendo explicarse en su práctica totalidad por el ciclo de los micrótidos, superpuesto a un aumento a largo plazo del esfuerzo de captura. Según los modelos matriciales basados en los valores promedio correspondientes a cada año del ciclo de los micrótidos, predicen que en dos de cada tres años la población disminuirá entre un 13% y un 15% anual, aunque ello se verá compensado por un considerable aumento durante el tercer año; asimismo, se calcula que el número de parejas nidificantes será bajo uno de cada tres años, sin ninguna tendencia a largo plazo, lo que concuerda con las estimaciones observadas acerca de los nidos activos

Towards integrated population monitoring based on the fieldwork of volunteer ringers: productivity, survival and population change of Tawny Owls Strix aluco and Ural Owls Strix uralensis in Finland

ABSTRACT Capsule: Monitoring of demographic parameters by volunteer ringers provides insight into the factors driving population changes in owls. Aims: To assess the value of national ringing, recapture and recovery data from volunteers to understand population dynamics. Methods: We analysed 49 years of ringing, recapture and recovery data from throughout Finland for Tawny Owls Strix aluco and Ural Owls Strix uralensis and compared them with annual population and productivity indices from other volunteer-based surveys. Results: Volunteer-based ringing data show that all aspects of the demography of Ural and Tawny Owls fluctuate dramatically in relation to an approximately three-year cycle of voles. When voles are abundant, a high proportion of owls breed and many young are produced; however, few of those young survive because vole populations crash the following winter. Survival of adults fluctuates less than that of young, suggesting that adults are better able to survive on alternative prey. In 2005, when vole populations remained high two years in row, many young were produced and survived, leading to a peak in owl breeding populations four years later at the top of the next vole cycle. This was immediately followed by a crash in populations suggesting a densitydependent interaction with vole abundance. Changing climate could affect owls both directly, by influencing winter survival, as well as indirectly through impacting prey availability. Conclusion: Encouraging similar, volunteer-based national-scale ringing efforts for owls elsewhere in Europe, especially for Tawny Owls which occur in most countries, would be a cost-effective way to understand how factors such as changing prey availability, climate and habitat availability are influencing the population levels of this and other raptors.Peer reviewe

Estudio comparativo de la adecuación temporal y de las rutas migratorias mediante el empleo de hallazgos de anillas y métodos de randomización

A method for comparing two migration routes is introduced. In the method are needed approximations of the average daily positions which are computed based on averages of dates and of positions in a window sliding through the encounters ordered in ascending order by date. The method contains two tests. The first, global, test statistic compares the entire migration routes and is the average of the distances between the daily positions of the two routes to be compared. The second test is used to identify sections during migration where the routes may deviate and is based on consecutive averages of the distances of short time periods between the daily positions of the two routes. A randomization test is used to assess the statistical significance of the test statistics in both components. The methods are applied to artificial and real data. Examples of the use of the method are computed with data sets of ring recoveries of Common terns (Sterna hirundo) and Ospreys (Pandion haliaetus) ringed in Finland in 1930–2002.El trabajo presenta un método para comparar rutas migratorias. El método utiliza aproximaciones para el cálculo de las localizaciones medias diarias basadas en las fechas y localizaciones promedio, en una ventana que se va desplazando a lo largo de las distintas observaciones ordenadas en orden ascendente según fecha. El método incluye dos pruebas estadísticas. La primera compara de forma global todas las rutas migratorias, y lo que se compara es la media de las distancias entre las distintas posiciones diarias de las dos rutas. La segunda prueba permite identificar tramos durante la migración en los que las rutas se pueden desviar, y se basa en promedios consecutivos de las distancias de breves períodos de tiempo entre las posiciones diarias de las dos rutas. Se utiliza una prueba de randomización para evaluar la relevancia estadística de las pruebas en ambos componentes. Los métodos se aplican a datos artificiales y reales. Los ejemplos del empleo del método se calculan con conjuntos de datos de recuperaciones de anillas de charranes comunes (Sterna hirundo) y de águilas pescadoras (Pandion haliaetus) anillados en Finlandia entre 1930 y 2002

A comparative study of Ural Owl Strix uralensis breeding season diet within its European breeding range, derived from nest box monitoring schemes

ABSTRACT Capsule: Voles are the main prey of the Ural Owl Strix uralensis in Europe, with larger prey and higher prey diversity being positively associated with owl breeding performance. Aims: To assess the breeding diet and its influence on the breeding performance of the Ural Owl across a north–south gradient of its European range using nest box monitoring data. Methods: Comparable monitoring of nest boxes in different biogeographical regions of Europe (Finland, Latvia, Slovenia) and diet analysis from nest samples to assess the taxonomic and trait influence of prey on owl breeding performance in different environments. Results: High plasticity in the Ural Owl hunting behaviour under different prey availability conditions resulted in significant differences between regions and years. Voles formed the highest proportion of the diet in all studied regions. Owl brood size was positively associated by higher proportions of voles and mice in the diet, and with increasing proportions of seasonally available larger prey and consequently prey diversity. Brood size was negatively associated with the proportion of non-mammalian and predominantly forest-living prey. Conclusions: The study highlighted the importance of comparative studies of raptor ecology across their geographical ranges in different environmental conditions to reveal undiscovered patterns, which may go undetected when conducting studies at the regional scale only.Peer reviewe

Estimating components of variance in demographic parameters of Tawny Owls, Strix aluco

Survival rates of Tawny Owls (Strix aluco) were estimated using recapture and recovery data from approximately 20,000 nestling and adult owls ringed between 1980 and 1999 in southern Finland. Survival rates averaged 33% in the first year of life, 64% in the second, and 73% in subsequent years, but varied dramatically among years. Approximately 50% of annual variation in survival could be explained by stage of the vole cycle and severity of winter weather. Capture probabilities, an index of breeding propensity, varied dramatically among years, and could almost entirely be explained by the vole cycle, superimposed on a long-term increase in capture effort. Matrix models based on mean values in each year of the vole cycle, predict that in 2 out of 3 years, the population would decline by 13%-15% per year, offset by a large increase in the 3rd year. Numbers of nesting pairs are predicted to be low in one of three years, with no long-term trend, consistent with observed estimates of active nests

Assessing space use by pre-breeding white-tailed eagles in the context of wind-energy development in Finland

The expansion of wind energy over large areas may be accompanied by major conflicts with birds, including birds of prey. Hence, it is desirable that the space use of species known to be vulnerable to wind energy be assessed in light of current and future developments. Here, we report on the large-scale dispersal movements of pre-breeding white-tailed eagles (Haliaeetus albicilla) in Finland, where a currently modest wind-energy capacity is expected to increase in the near future. We studied white-tailed eagle space use with a particular focus on the potential for annual power production (GWh) at specific locations, as estimated by the Finnish Wind Atlas. Also, we aimed to detect a potential human-wildlife conflict by assessing white-tailed eagle space use against the spatial distribution of existing and recently proposed wind farms. We found that, despite visiting a large proportion of the country, the eagles stayed primarily within coastal areas and islands, restricted to where human infrastructure was present only at very small amounts. Because of the distribution of wind resources, such areas were found to contain considerable potential for power production. The eagles visited most of the areas targeted for wind-energy development. However, these areas did not coincide with a higher-than-average eagle relocation frequency, suggesting that the existing and recently proposed wind farms do not represent an elevated threat to dispersing eagles. Caution should nevertheless be taken against interpreting that co-occurrence poses no threat at any given site, as site selection is paramount to avoid conflicts with avian conservation.Peer reviewe

A review of raptor and owl monitoring activity across Europe : its implications for capacity building towards pan-European monitoring

ABSTRACT Capsule: A questionnaire identified 1196 raptor monitoring species schemes within 236 monitoring programmes across 37 countries. Aims: To assess the level of monitoring of status/trends of raptors across Europe, to produce a webbased inventory of activities. Methods: A questionnaire promoted by voluntary national coordinators assessed monitoring coverage, focusing on breeding populations. Results: One thousand one hundred and ninety-six species schemes (236 monitoring programmes; 90% active in 2012) were reported from 37 countries. Sixty per cent of schemes were of over 10 years duration and nine countries ran schemes of over 40 years duration. Nineteen species had at least one scheme in 10 or more countries, and 15 species had schemes that ran for over 10 years. Thirteen species had breeding monitoring schemes in over 50% of countries where they breed, including widespread species (e.g. Peregrine Falcon Falco peregrinus) and localized species (e.g. Rough-legged Buzzard Buteo lagopus). Lanner Falcon Falco biarmicus, Levant Sparrowhawk Accipiter brevipes and Booted Eagle Hieraaetus pennatus had the least representative coverage, and four rare species had no coverage. Coverage was more representative in north and west Europe than further south and east. Coverage was more representative for widespread species and those with more favourable conservation status. Conclusions: Large potential exists to enhance reporting on status/trends, ecotoxicology analyses and volunteer-based monitoring at the pan-European scale. National coordinators provide an ideal network to develop and disseminate best practice guidance across Europe.Peer reviewe

Petolintuvuosi 2021 - sinnitellen kohti seuraavaa

Non peer reviewe

The migration of the great snipe Gallinago media: intriguing variations on a grand theme

The migration of the great snipe Gallinago media was previously poorly known. Three tracks in 2010 suggested a remarkable migratory behaviour including long and fast overland non-stop flights (Klaassen et al. 2011). Here we present the migration pattern of Swedish male great snipes, based on 19 individuals tracked by light-level geolocators in four different years. About half of the birds made stopover(s) in northern Europe in early autumn. They left the breeding area 15 days earlier than those which flew directly to sub-Sahara, suggesting two distinct autumn migration strategies. The autumn trans-Sahara flights were on average 5500 km long, lasted 64 h, and were flown at ground speeds of 25 m s-1 (90 km h-1). The arrival in the Sahel zone of West Africa coincided with the wet season there, and the birds stayed for on average three weeks. The birds arrived at their wintering grounds around the lower stretches of the Congo River in late September and stayed for seven months. In spring the great snipes made trans-Sahara flights of similar length and speed as in autumn, but the remaining migration through eastern Europe was notably slow. All birds returned to the breeding grounds within one week around mid-May. The annual cycle was characterized by relaxed temporal synchronization between individuals during the autumn-winter period, with maximum variation at the arrival in the wintering area. Synchronization increased in spring, with minimum time variation at arrival in the breeding area. This suggests that arrival date in the breeding area is under strong stabilizing selection, while there is room for more flexibility in autumn and arrival to the wintering area. The details of the fast non-stop flights remain to be elucidated, but the identification of the main stopover and wintering areas is important for future conservation work on this red-listed bird species