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Density and diversity of hole-nesting passerines: dependence on the characteristics of cavities

100%

Remm J., Lohmus A., Rosenvald R.

Acta Ornithologica

2008

tom 43

nr 1

83-91

In addition to the well-known limiting effect of cavity abundance on the density of hole-nesting passerines, other aspects of cavity availability may shape their communities as well. Notably, where there is a considerable aggregation of cavities, territory-holders may prevent the occupation of the nearest cavities by other birds, whereas a supply of diverse cavities may reduce interspecific competition. We used multivariate general linear models to explore whether, and how, variables describing the supply of small cavities are related to the density and diversity of hole-nest- ing passerine communities in 33 hemiboreal old forest stands. The total density of 12 species (1.3 ± 0.8 pairs/ha) increased with cavity density and diversity, but was not affected by cavity aggregation. As expected, cavity diversity also promoted bird diversity; indeed, the densities of different species were positively related to the densities of different cavity types. The results indicate that segregation in nest-cavity selection affects the co-occurrence of passerine species and, at the mean densities of small tree-cavities in the region (2.3/ha), cavity aggregation does not markedly reduce their availability. In conservation management, therefore, it is important to maintain a diverse supply of cavities in addition to their abundance, in order to sustain hole-nester communities.

Absence of edge effects on nest predation in the Collared Flycatcher Ficedula albicollis in the primeval forest of Bialowieza National Park, NE Poland

80%

Stanski T., Walankiewicz W., Czeszczewik D.

Acta Ornithologica

2008

tom 43

nr 1

92-96

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.

Ograniczanie wyników

2 Acta Ornithologica

1 Czeszczewik D.

1 Lohmus A.

1 Remm J.

1 Rosenvald R.

1 Stanski T.

1 Walankiewicz W.

2 2008

Wyniki wyszukiwania

Density and diversity of hole-nesting passerines: dependence on the characteristics of cavities

Absence of edge effects on nest predation in the Collared Flycatcher Ficedula albicollis in the primeval forest of Bialowieza National Park, NE Poland