Ornis Fennica

In Northern Europe, the Mistle Thrush (Turdus viscivorus) is a relatively poorly studied species inhabiting forested landscapes where it has historically experienced population declines. Those declines have been attributed to the spread of intensive forest management; yet, the populations have stabilized or increased in recent decades. To distinguish the main forestry impacts on its breeding numbers and distribution, a multiple-visit territory-mapping study was carried out over 15 km2 of production forest landscape in Estonia. At the landscape scale, the breeding distribution was concentrated to conifer forests on bog peat where the densities were five times higher than in other conifer forests and (at least) ten times higher than in non-conifer forests. This reveals a broad distribution pattern where high-density (core) habitats only host a small fraction of the total population; their relative contribution to the recruitment remains unknown. At the breeding territory scale (within 150 m from a nest), Mistle Thrushes avoided recent clear-cuts and preferred larger areas of old stands more than expected from the distribution of suitable stands for nesting. This indicated that, in a short term, clear-cutting reduces nesting habitats of this species disproportionately more than expected from the cut area alone; this is in accordance with the documented 20th century declines of the species in Fennoscandia. The relationship with forestry drainage is more complicated, however, due to delayed effects and covariation with the main breeding habitat. The basic ecology of the species in conifer forest-wetland landscapes, which are subjected to management pressures, warrants future studies and might provide general insights into the dynamics and functioning of these ecosystems.

Although the Great Spotted Woodpecker (Dendrocopos major) is the most common of the European woodpecker species, there are no studies detailing its foraging behaviour in the breeding and non-breeding seasons. Our research, conducted in the primeval oak-lime-hornbeam forest of the Białowieża National Park in 1999–2011, compared foraging sites and foraging techniques used by this species in these two seasons. Great Spotted Woodpecker predominantly foraged on standing trees, while lying trees and the ground were occasionally used as foraging sites, but almost exclusively in the breeding season. European hornbeam (Carpinus betulus) and small-leaved lime (Tilia cordata) were the most frequently used for foraging in the breeding season, whereas Norway spruce (Picea abies) and pedunculate oak (Quercus robur) were used in the non-breeding season. Great Spotted Woodpecker foraged more frequently on dead and large trees in the non-breeding season. In the breeding season, Great Spotted Woodpecker collected food mainly from living substrates, predominantly sites on large diameter trunks and at low height, while in the non-breeding season it collected food from thin, dead and upper branches. Searching for food and gleaning it from the tree surface was the most common foraging technique used in the breeding season, whereas seed extraction from cones dominated in the non-breeding season. The percentage of foraging time spent on this type of food was positively correlated with the index of Norway spruce seed production. Our study showed that the foraging behaviour of the Great Spotted Woodpecker in the two seasons differs significantly due to changes in food resources.

The field studies were conducted in three ephemeral river islets of the middle Pripyat River, southern Belarus in 2006–2007. Nestlings of the Northern Lapwing (Vanellus vanellus) were ringed soon after hatching, and reencountered during subsequent visits. Post-hatching survival was estimated by capture-mark-recapture models. Daily survival rates of the Northern Lapwing chicks were very high, varying between 0.90 and 0.99, and the cumulative survival rates over 35 days between hatching and fledging were 0.54 and 0.70 in 2006 and 2007, respectively. Survival rate was lower in the first ten days of life, which is similar to that reported in other precocial species. The key factor supporting this high breeding success is low predation due to nesting of lapwings on periodic river islets that naturally restrict access by mammalian predators and apparent scarcity of terrestrial and avian predators. River islet habitats with co-occurrence of dry and wet fertile microhabitats provide optimum feeding conditions for the Lapwing chicks with a wide range of aquatic, ground and surface invertebrates. Moreover, semicolonial breeding of the Northern Lapwing (about 30 nests/ha) with other waders, terns and gulls increases the effectiveness of anti-predator behaviour. Consequently as a result of low predation pressure and good foraging conditions, in 2006 and 2007, productivity was 2.1 and 2.8 fledged young per single nest with four chicks respectively, a value hardly reported in Europe, except in managed sites.

We estimated the onset of natal dispersal for a large diurnal raptor with high propensity towards large-scaled exploratory movements during the post-fledging period, the White-tailed Sea Eagle (Haliaeetus albicilla). We analysed GPS tracking data of 21 juveniles with respect to the onset of natal dispersal comparing six methods available from the recent literature. While none of the methods significantly differed from the visual method, the Distance Threshold method underestimated the dispersal onset for some individuals. Likewise, coefficient of variation methods overestimated the dispersal onset in few cases, presumably because the temporal scale of available GPS fixes did not correspond to the scale of discrete dispersal movements. We conclude that all tested methods are generally suitable to estimate the dispersal onset, specifically if the research question does not depend on an exact but rather a rough estimate. A visual determination might increase flexibility to account for individual behavior and yields consistent results across individuals, but highly reduces the comparability across observers and studies. For research questions relying on exact estimates, we propose using a combination of an automated method and a visual determination as a back-up method for single individuals with clear under- or overestimation. An exploratory comparison showed that the temporal resolution of the GPS may further affect the accuracy of natal dispersal estimates. For individuals with clear movement patterns, high-resolution movement data could increase the accuracy of Coefficient of Variation methods. We underline the necessity for further investigation on the effects of temporal resolution on dispersal onset estimates.

The Eurasian Treecreeper is a forest bird distributed from South-Western Europe up to Northern Asia. Two phylogenetic groups have been recently identified within this species, one restricted to Corsica Island (Mediterranean) and the Caucasus region, the other distributed over most of Eurasia and in Northern Asia. Little is known on the natural history of the Corsican population. We present here new comprehensive data on its distribution and habitat. The Eurasian Treecreeper is found from sea level to the upper limit of the forest but absent from the treeless macchia, a dominant vegetation in Corsica. Breeding occurs in a variety of tree species with a strong preference for mature stands and large trees. Its preferred habitat consists of old stands of Corsican Pines and of Sweet Chestnuts, although they are not the commonest tree species in Corsica. The current decline of Sweet Chestnut orchards confers a particular importance to the future preservation of mature stands of Corsican Pine, a patrimonial habitat of great value hosting several endemic bird taxa.