Foraging Niches in a Passerine Bird Community in a Grey Alder Forest in Central Norway

Publication Type:Journal Article
Year of Publication:1982
Authors:Sæther, B-E
Journal:Ornis Scandinavica
Date Published:1982
ISBN Number:00305693
Keywords:Acrocephalidae, Fringilla, Fringilla coelebs, Fringillidae, Hippolais, Hippolais icterina, Norway, Parus
Abstract:The foraging niches in a passerine bird community in a grey alder forest in Central Norway (63°N) were studied during the breeding seasons along four niche dimensions, viz. 'structural layer', 'tree species', 'foraging height' and 'horizontal position'. The Fringilla and Parus species were more frequently seen on the ground in late April and early May, compared to later in the season. Within the tree layer, pronounced seasonal and annual variation was particularly found within the 'tree species' dimension. Within the tree layer the species seemed most separated in the 'foraging height' dimension. Only weak and insignificant correlation coefficients were found between overlap values or niche breadth values in different dimension. Morphological similarity was not correlated with the degree of overlap in any foraging dimension. Similarly, positions in the morphological space did not predict the species' foraging niches. In the 'tree species' dimension a low degree of overlap with the rest of the bird species was associated with high niche breadth values, while an inverse relationship was found in the 'foraging height' dimension. As no linear trends were discernable in the three-dimensional space between niche breadth and mean niche overlap values, it is suggested that separation may be increased by either widening the range of explotation (e.g. Fringilla coelebs), or by concentrating effort on a more restricted part (e.g. Hippolais icterina).
Short Title:Ornis Scandinavica
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