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

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

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

Finnish Ospreys 1971–2017: Conservation and Research

The Osprey (Pandion haliaetus) breeds all over Finland: from the southern archipelago (60o N) to the northernmost Lapland (70o N). The Finnish Osprey population decreased in the late 19th and early 20th century due to persecution. During the World War II Osprey population recovered slowly, but decreased again from the 1950s to early 1970s, because of (1) persecution during migration and wintering, (2) the impact of contaminants, particularly of the DDT, and (3) the lack of old flat-topped trees for nesting. In 1971, I launched together with the Finnish Ringing Centre The Project Pandion with the following aims: (1) to monitor annual changes and long-term trends in the population size, productivity, survival and dispersal and (2) to verify the effects and to estimate the importance of potential negative human factors (persecution, environmental contaminants, forestry, commercial fishing, recreation etc.) on the welfare of the Finnish Ospreys. This presentation is mainly based on the results of Project Pandion

Estimating age-specific survival rates of tawny owls--recaptures versus recoveries

We compared estimates of annual survival rates of tawny owls ( Strix aluco ) ringed in southern Finland from several different sampling methods: recoveries of birds ringed as young; recaptures of birds ringed as young; recoveries of birds ringed as adults as well as young; combined recoveries and recaptures of birds ringed as young, and combined recoveries and recaptures of birds ringed as adults and young. From 1979 to 1998, 18 040 young owls were ringed, of which 983 were recaptured as breeders in subsequent years during this period, and 1764 were recovered dead at various locations. In addition, 1751 owls were ringed as adults, of which 612 were later recaptured and 199 were recovered dead. First-year survival rates estimated using only recoveries of birds ringed as young averaged 48%, while apparent survival rates estimated using only recaptures from birds ringed as young averaged 10-13%. Use of combined recapture-recovery models, or supplementary information from recoveries of birds ringed as adults, produced survival estimates of 30-37%. Survival estimates from young-recoveries-only models were biased high, because of violation of the assumption of constant recovery rates with age: birds dying in their first-year were one-third less likely to be found and reported than older birds. In contrast, recaptures-only models confounded emigration with mortality. Despite these differences in mean values, annual fluctuations in estimated first-year survival rates were similar with all models. Estimates of adult survival rates were similar with all models, while those for second-year birds were similar for all models except recaptures-only. These results highlight the potential biases associated with analysing either recaptures or recoveries alone of birds ringed as young, and the benefits of using combined data.