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

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

Petolintuvuosi 2021 - sinnitellen kohti seuraavaa

Non 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