Detailed knowledge of the foraging behaviour of endangered species, especially in relation to available resources, may be useful in conservation management. I studied the year-round foraging behaviour of the White- backed Woodpecker in broadleaved, primeval Białowieża Forest (NE Poland), and investigated how foraging time was divided among various substrates and foraging techniques. Of the 13 tree species used for foraging, woodpeckers were most frequently recorded utilising the three most common tree species: hornbeam Carpinus betulus, lime Tilia cordata and spruce Picea abies (totalling 61-68% of observed time), and the proportional use of tree species did not change seasonally. Observations of birds foraging on snags increased and foraging on fallen trees decreased from spring to winter. Foraging was most frequently recorded on dead substrates (72-85%), usually those covered with bark. Mean time of foraging on an individual tree increased significantly from spring to winter. The foraging techniques most often used by woodpeckers were bark-pecking (29-11%) and superficial wood-pecking (12-27%). During winter, foraging techniques did not change significantly in relation to weather. These results suggest that forest stand composition is less important to this species than tree condition. Most broadleaved tree species and, under some conditions, spruce can be utilised for foraging by this woodpecker if they provide dead or dying substrates.
Broods of Pied Flycatcher nesting in natural tree holes and nest-boxes in Białowieża Forest (E Poland) were compared. Natural holes in primeval stands of the Białowieża National Park were located by following singing males, then monitored several times during the season. Nest-boxes situated in the managed part of the forest were inspected weekly. Flycatchers breeding in natural holes started laying eggs on average two days later (15 May) and laid smaller clutches (6.4 eggs) than birds breeding in nest-boxes (13 May and 6.7 eggs). The predation rate was significantly lower in natural holes (av. 47%) than in nest-boxes (av. 65%). This result indicates that generalisations regarding the evolution of adaptations to predation by nest-box populations should be treated with caution.
W latach 1992-1995 badaliśmy wpływ daty przylotu i wieku samca muchołówki białoszyjej Ficedula albicollis (wtórny dziuplak, zimujący w Afryce) na jakość miejsca lęgowego. Dane zbierano w grądach Białowieskiego Parku Narodowego od połowy kwietnia do ok. 20 maja. Za datę przylotu uznano dzień, w którym po raz pierwszy zaobserwowano śpiewającego i wchodzącego do dziupli samca. Wśród samców, na podstawie upierzenia, wyróżniono dwie grupy: młode (jednoroczne) i stare (dwuletnie i starsze). Za jakość dziupli przyjęto jej parametry (wysokość nad ziemią, wielkość otworu wlotowego, głębokość i powierzchnię dna). Określono terminy przylotów 216 samców oraz zmierzono ponad 300 dziupli. Młode samce przylatywały średnio 4 dni później (tab. 1, ryc. 1), mimo to jakość wybranych przez nie miejsc gniazdowych nie różniła się. Również korelacja między datą przylotu a poszczególnymi parametrami dziupli była statystycznie nieistotna (tab. 2 i 3). Świadczy to o nadmiarze dobrych miejsc gniazdowych i braku ostrej konkurencji o dziuple w grądach naturalnych Białowieskiego Parku Narodowego.
We studied the fluctuation in 1975-1997 numbers of two species: the Pied Flycatcher Ficedula hypoleuca and the Collared Flycatcher F. albicollis breeding in natural cavities in the primeval deciduous stands of the Białowieża National Park (NE Poland). Both studied birds are commonly regarded as competitors if sympatric. Densities of two flycatchers are positively correlated within 7 plots (pooled data) investigated by a territory mapping method over 22 years (r = 0.71, p < 0.05) and 36 ha plot studied very intensively through 9 years (r = 0.35, p < 0.05). We found no evidence that the Pied Flycatcher density is negatively affected by the dominant Collared Flycatcher when that stronger species has a higher density. Clearly, both species fluctuated in a parallel way which contradicts an earlier generalization. The Pied Flycatcher breeds in Białowieża deciduous stands in much lower densities than the Collared Flycatcher does.
Distribution of Three-toed Woodpeckers and that of dead wood were mapped in two fragments of the Białowieża National Park (BNP) differing in their management history — primeval (old-growth stands of natural origin, no human intervention) and logged (as the former but subject to 80 years of commercial forestry). Data were collected during the breeding seasons 1999-2001. In the end of April 2000, the whole BNP was systematically searched; playbacks of drumming were used to enhance detection of birds. Presence/absence of Three-toed Woodpeckers and of dead wood (standing and downed Norway spruces and snags of other trees) were recorded within each forest sub-compartments (ca. 28 ha). Data from censuses done in smaller plots in 1975-1999 showed that in the primeval forest the woodpeckers bred twice more frequently in swampy and coniferous forests than in the oak-hornbeam habitat. These preferred habitat types covered larger areas in the logged fragment than in the primeval part (66% vs. 41%). Yet despite this, Three-toed Woodpeckers were recorded there over twice less frequently (14% of 176 sub-compartments) than in the primeval (36% of 164 sub-compartments) part. These differences followed sharp contrasts in the dead wood availability; all but one sub-compartments in the primeval fragment contained some form of dead wood, whereas dead spruces were missing in almost 30% of sub-compartments in the logged part. This was the effect of continuous "sanitary" logging, purposeful removal of dying and dead spruces from the Forest. To restore Three-toed Woodpecker habitats it is necessary to ban removal of dead spruces in the managed part of BNP. However, the BNP area is too small, to assure the long-term survival of the Białowieża Forest population. To achieve this, it is necessary to resign from removal of dying and dead spruces in the whole Polish part of the Białowieża Forest (600 km²). This would create breeding habitat for a maximum 260-320 pairs.
The territory mapping technique censuses of the Collared Flycatcher F. albicollis were conducted on 25.5 ha plot in the Białowieża National Park. Conducted at the same time within the same plot, an intensive study on the ecology of the Collared Flycatcher allowed us to precisely assess the true number of breeding pairs (all nests were found). The combined version of mapping technique yields numbers which are an average 67% (min. 54, max. 92%) of the true numbers of the F. albicollis breeding pairs. This underestimation is negatively related both to the breeding losses in the Collared Flycatcher (r = -0.87, p = 0.010) and to its breeding density (r = -0.64, p = 0.125). Despite this underestimation the year-to-year changes in numbers obtained by both methods are positively correlated and highly significant (r = 0.84, p = 0.017). After an arithmetical formula was applied (i.e. 1.82 * mapping result - 7.33) only an average 14% of bias occurred.
Nest predation is a major factor limiting breeding bird populations in primeval tree stands. Factors such as food limitation, availability of nesting sites or competition are not so important. Nest predation is usually more common along the edges of forests than in their interiors. The aim of this study was to determine how breeding losses in the secondary cavity-nester Collared Flycatcher Ficedula albicollis that bred in natural holes varied with distance from the forest edge in primeval stands of the Białowieża National Park (NE Poland). A comparison of the breeding losses along the edges and in the interiors revealed no statistical differences. The main nest predators were the forest species Apodemus flavicollis, Martes martes, and Dendrocopos major. It is better to keep forest tracts unfragmented, with a belt of bushes and thickets or woodland in an early successional stage along the edge. This would protect forest birds from predators living in open habitats.
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