Veli-Matti Väänänen

The scientific basis for a new and sustainable management of migratory European ducks

Abstract It is an axiom in ecology that knowing the sheer number of individuals in a population is of very little help if the objective is to understand future and past changes in population size. Yet, this is exactly how migratory European ducks are monitored, many of which are important quarry species in several countries. We argue that present monitoring is insufficient to address objectives of wise use andsustainabilitysuchasthoseemphasisedinrecentmanagementdirectivesand multilateral international agreements. The two main problems are the almost total lack of reliable data on recruitment and mortality. We advocate a pan-European monitoring system based on undisputed scientific principles; i.e. a long-term, coordinated and standardised scheme that produces data about vital rates of duck populations as well as about harvest size. Data from such a scheme can be used by game biologists to produce predictive tools, thus providing a functional basis for management decisions for adaptive harvesting and conservation alike.

Molecular Epidemiology of Outbreak-Associated and Wild-Waterfowl-Derived Newcastle Disease Virus Strains in Finland, Including a Novel Class I Genotype

ABSTRACT Newcastle disease (ND) is a highly contagious, severe disease of poultry caused by pathogenic strains of Newcastle disease virus (NDV; or avian paramyxovirus-1). NDV is endemic in wild birds worldwide and one of the economically most important poultry pathogens. Most of the published strains are outbreak-associated strains, while the apathogenic NDV strains that occur in wild birds, posing a constant threat to poultry with their capability to convert into more virulent forms, have remained less studied. We screened for NDV RNA in cloacal and oropharyngeal samples from wild waterfowl in Finland during the years 2006 to 2010: 39 of 715 birds were positive (prevalence, 5.5%). The partial or full-length F genes of 37 strains were sequenced for phylogenetic purposes. We also characterized viruses derived from three NDV outbreaks in Finland and discuss the relationships between these outbreak-associated and the wild-bird-associated strains. We found that all waterfowl NDV isolates were lentogenic strains of class I or class II genotype I. We also isolated a genetically distinct class I strain (teal/Finland/13111/2008) grouping phylogenetically together with only strain HIECK87191, isolated in Northern Ireland in 1987. Together they seem to form a novel class I genotype genetically differing from other known NDVs by at least 12%.

How many juvenile Teal Anas crecca reach the wintering grounds? Flyway-scale survival rate inferred from wing age-ratios

Autumn postnuptial migration is critical in the dabbling duck annual cycle, when first-year birds in particular suffer high losses to natural and hunting mortality. Mortality rates in this age-class are generally unknown in Europe where winter ringing predominates. We used data from large-scale wing collections from hunters in Finland, Denmark and France to test the prediction that juvenile proportions among killed Teal (Anas crecca) would decline with distance along the flyway. As expected, this proportion decreased from 89% in Northern Finland to 58% in Western France. Potential biases linked with age determination from the wings, differential migration of age-classes, relative susceptibility to different forms hunting and gradual improvement of juvenile survival as they learn to avoid hunters could not explain the observed decline of juveniles in the shot population. This pattern was therefore considered to be genuine, the result of the cumulative depletion of first-years along the flyway, likely through hunting. On this assumption, combined with known adult monthly survival rates during August–November (94.2%), monthly juvenile survival rate was estimated at 52.8%, i.e. 14.7% (range 13.9–15.4% based on extreme values of adult survival) amongst Scandinavian juveniles reaching wintering quarters in Western France. Despite lack of precision in such estimates based on relative proportions, there is little doubt about the magnitude of autumn juvenile mortality and its consequences for the population dynamics of Teal. Lack of correlations between annual proportions of juveniles in the hunting bag and an index of Teal breeding success in Finland may result from such high and variable inter-annual mortality.

Hunting Disturbance and the Timing of Autumn Migration in Anas Species

In Europe, waterfowl hunting is a popular recreational activity, especially in waterfowl staging and wintering areas, but also in breeding areas such as Finland. This paper gives an account of hunting disturbance, timing of autumn migration and refuge use in Anas species in eutrophic wetlands in central Finland (63°N, 27°E) during 1995-1999. Based on the timing of migration, duck species may be divided into early and late migrants. In two lakes (total area 2.2 km^2) which were monitored on a weekly basis during 1995-1998, numbers of late migrants, i. e. mallard Anas platyrhynchos, teal Anas crecca and wigeon Anas penelope, increased towards the opening of hunting season on 20 August, whereas shoveler Anas clypeata, pintail Anas acuta and garganey Anas querquedula migrated early, and peak numbers of these species occurred already in the beginning of August. Consequently, in Finlands inland lake area, hunting disturbance relates differently to early and late migrating species. Immediately after the opening of the season the numbers of dabbling ducks collapsed and the average numbers in the wetlands were only 9.3% of the numbers present at the end of the protection period in 1995-1998. A corresponding decrease in numbers occurred in 13 lakes (total area 8.5 km^2) in the Finnish inland lake district in 1999. After the beginning of the open season numbers of wigeon, teal and mallard decreased in unprotected areas, but increased in a refuge area. In Finland, refuge areas with high-quality foraging and moulting habitats for waterfowl are few, so a network of waterfowl reserves could mitigate the effects of hunting disturbance.

Competitive effects of fish in structurally simple habitats: perch, invertebrates, and goldeneye in small boreal lakes

We determined the associations between Eurasian perch Perca fluviatilis, invertebrates, and common goldeneye Bucephala clangula in boreal lakes. Our aim was to test the hypothesis that perch play a controlling role in small, oligotrophic, acidic, and poorly vegetated boreal lakes, affecting both invertebrate numbers and community structure. In addition, we predicted that perch impact lake usage by goldeneye. In the observational part of our study, we first explored the association between perch, invertebrates and goldeneye (pairs and broods per shore km) in 18 boreal, poorly vegetated lakes. Perch densities were associated negatively with invertebrate abundance and lake usage by goldeneye broods. In the experimental part in three fish-free lakes, we found that upon successful perch introductions, the number and biomass of invertebrates, the proportion of large dytiscids, and lake usage by goldeneye broods significantly decreased. We conclude that perch apparently plays a key role as a predator of invertebrates in boreal lakes with few aquatic macrophytes. It is evident that perch can strongly affect their prey populations and communities, and this predation may have an indirect effect on species, e.g. goldeneye, that consume the same prey.

Fish–duck interactions in boreal lakes in Finland as reflected by abundance correlations

We studied the hypothesis that fish play an important role in lake use by ducks (pairs and broods) in boreal lakes. The study was based on densities of different duck and fish species in 28 boreal lakes in southern Finland. We focused on the three most common duck species (mallard Anas platyrhynchos, green-winged teal A. crecca and common goldeneye Bucephala clangula) and on the three most common fish species (perch Perca fluviatilis, roach Rutilus rutilus and pike Esox lucius) in the region. We considered both competitive and predatory interactions between ducks and fish, the perch and roach being potential competitors with ducks and the pike a potential predator of ducks. We found a negative association between green-winged teal brood density and total fish density, the other duck species having only a weak association with total fish density. When the three fish species were considered separately, a negative association, suggesting food competition, was found between perch, green-winged teal and goldeneye, whereas the role of roach as a food competitor seemed to be of minor importance. We did not find any clear signs of predatory effects of pike on ducks. Our results suggest that food competition is a more important factor than pike predation in affecting lake use by ducks in oligotrophic boreal environments in southern Finland.

Alien Grazing: Indirect Effects of Muskrats on Invertebrates

Effects of alien herbivores on plants are quite well known, especially on oceanic islands. Much less is known about the indirect effects of alien herbivores. Via indirect effects indigenous organisms can become more vulnerable to other ecological factors. We studied the effect of dense muskrat population on aquatic invertebrates in patches, which were in different succession phases after grazing. The succession was divided into three phases:(i) open-water area, (ii) mixed floating and submerged vegetation, and (iii) undisturbed Equisetum stands. Intensive muskrat grazing affected especially the size distribution of invertebrates. The proportion of small invertebrates was greatest in clear-cut areas, whereas that of large invertebrates was greatest in the Equisetum-stands. According to activity traps, the clear-cut areas harboured good populations of small perch, which are known as invertebrate predators. The study showed that the indirect effects of alien herbivore can be considerable. In this case, they seemed to be mediated to invertebrates through the change in vegetative habitat structure. This change rendered invertebrates more vulnerable to fish predation.

Factors Affecting Changes in Waterfowl Populations in Eutrophic Wetlands in the Finnish Lake District

From the 1970s to the 1990s, changes in breeding waterfowl populations were monitored at 26 well-vegetated lakes in southern Finland. Extreme total population levels were found to differ by 40%, but between successive years fluctuations did not exceed 20%, the most unstable populations being garganey Anas querquedula, tufted duck Aythya fuligula, coot Fulica atra and pochard Aythya ferina. Multiple regression analysis was used to determine the effects of weather factors during wintering, spring and brood seasons on the variation in breeding waterfowl populations. The following weather factors were statistically significant in explaining fluctuations observed in four species; in garganey: spring temperature; in pintail Anas acuta: brood season temperature, winter severity in France and spring temperature; in goldeneye Bucephala clangula: winter severity in the Baltic and spring temperature; and in mallard Anas platyrhynchos: brood season temperature of the previous year. Mallard, teal Anas crecca, wigeon Anas penelope and goldeneye were shot in larger numbers than would be expected considering their respective proportions of the breeding waterfowl community. Hunting pressure on mallard, tufted duck and goldeneye was clearly higher in our study area than in other parts of Finland. Our results indicate that the level of hunting pressure in our study area may affect population densities of mallard.

Molecular epidemiology of H9N2 influenza viruses in Northern Europe.

Low pathogenic avian influenza viruses are maintained in wild bird populations throughout the world. Avian influenza viruses are characterized by their efficient ability to reassort and adapt, which enables them to cross the species barrier and enhances their zoonotic potential. Influenza viruses of the H9N2 subtype appear endemic among poultry in Eurasia. They usually exist as low-pathogenic strains and circulate between wild bird populations, poultry and birds sold at live bird markets. Direct transmission of H9N2 viruses, with receptor specificities similar to human influenza strains, to pigs and humans has been reported on several occasions. H9N2 virus was first encountered in Finland in 2009, during routine screening of hunted wild waterfowl. The next year, H9N2 influenza viruses were isolated from wild birds on four occasions, including once from a farmed mallard. We have investigated the relationship between the reared and wild bird isolates by sequencing the hemagglutinin and the neuraminidase genes of the Finnish H9N2 viruses. Nucleotide sequence comparison and phylogenetic analyses indicate that H9N2 was transmitted from wild birds to reared birds in 2010, and that highly identical strains have been circulating in Europe during the last few years.

Drivers of breeding numbers in a long-distance migrant, the Garganey (Anas querquedula): effects of climate and hunting pressure

AbstractA multitude of anthropogenic factors are threatening bird populations but their roles as drivers of population changes are generally poorly understood. Several duck species, for instance, have unfavorable conservation status at the Pan-European level but in most cases we do not know why the species have been declining, nor do we know actual drivers of their population dynamics. We studied population dynamics of the Garganey (Anas querquedula), a quarry species with unfavorable conservation status at the Pan-European level. As a trans-Saharan migrant, Garganey is potentially highly vulnerable to climate change impacts. We used long-term (1989–2012) data of breeding numbers from a study area in central Finland and assessed the relative importance of three climatic variables (representing conditions in wintering areas and during spring migration) and local hunting pressure in explaining the interannual variation in breeding numbers. Population size of Garganey showed a decreasing trend over the study period but also considerable interannual variation. Spring temperature in southern Finland was the most important factor in explaining interannual variation in breeding numbers. Rainfall in the wintering areas was also of importance, whereas the NAO (North Atlantic Oscillation) and local hunting pressure appeared not to be important. Our results suggest that weather conditions during spring migration largely drive interannual variation in Garganey breeding numbers at the NW edge of the species’ range. However, positive effects of warm springs may be counteracted by negative effects of drought in the wintering areas.ZusammenfassungEinflussfaktoren auf Brutpaarzahlen bei einem Langstreckenzieher, der Knäkente (Anas querquedula): klimatische Effekte und Jagddruck Eine Vielzahl anthropogener Einflussfaktoren bedrohen Vogelpopulationen. Ihre Rolle hinsichtlich Populationsveränderungen ist jedoch allgemein nur wenig verstanden. Verschiedene Entenarten beispielsweise besitzen einen unzureichenden Schutzstatus auf pan-europäischer Ebene. In den meisten Fällen sind weder die Gründe für die Rückgänge der Arten bekannt, noch sind die derzeitigen Auslöser für ihre Populationsdynamiken verstanden. Wir untersuchten die Populationsdynamik von Knäkenten (Anas querquedula), eine Zielart mit ungünstigem Erhaltungszustand auf pan-europäischer Ebene. Als Transsaharazieher sind Knäkenten potentiell stark gefährdet im Hinblick auf Auswirkungen des Klimawandels. Wir nutzten Langzeitdaten (1989–2012) zu Brutpaarzahlen aus einem Untersuchungsgebiet in Zentralfinnland und bewerteten die relative Bedeutung dreier klimatischer Faktoren (repräsentativ für die Bedingungen in den Überwinterungsgebieten und während des Frühjahrszuges) sowie den lokalen Jagddruck zur Erklärung von interannuellen Schwankungen im Brutbestand. Die Knäkenten-Population zeigt einen abnehmenden Trend während des Betrachtungszeitraumes, jedoch mit deutlichen Schwankungen zwischen den Jahren. Die Frühjahrstemperatur in Südfinnland war der wichtigste Faktor zur Erklärung der variierenden Brutpaarzahlen zwischen den Jahren. Außerdem war der Niederschlag in den Überwinterungsgebieten ebenfalls von Bedeutung, wohingegen die NAO (Nordatlantische Oszillation) und der lokale Jagddruck unerheblich zu sein schienen. Unsere Ergebnisse deuten daraufhin, dass die Wetterbedingungen während des Frühjahrszuges weitgehend die jährlichen Schwankungen der Brutpaarzahlen von Knäkenten an der nordwestlichen Grenze ihres Verbreitungsgebietes bewirken. Allerdings könnten die negativen Effekte von Dürren in den Wintergebieten den positiven Auswirkungen von warmen Frühjahren entgegenwirken.