Sexual dimorphism and divergence in winter foraging behaviour of three-toed woodpeckers Picoides tridactylus

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Measurements of 48 males and 45 females of Three-toed Woodpeckers (Picoides tridactylus) shot in Norway revealed that the mean lengths of wing, tail, bill and tarsus of males were significantly greater than those of females. Sexual dimorphism was most marked for the bill and tarsus. Feeding observations of the species from spruce-dominated mixed forests during the October-March period indicated an intersexual partitioning of the foraging niche. The males exhibited a stereotyped foraging pattern of bark scaling low down on the main trunks of dead spruce, whilst females used a more differentiated feeding technique and utilized a greater variety of trunk and branch sizes of dead, decaying and living trees of several different species. Significant intersexual differences were found in tree height preference and in the diameter of trunks and branches. The males foraged almost exclusively on the trunks of trees over 10 m high and over 15 cm in diameter, whilst females often frequented dead spruce, under 5 m high, and foraged on thinner trunks and branches. Foraging height was significantly lower for males than for females. The relationship between the sexual dimorphism, the intersexual partitioning of the feeding niche and their biological significance, is briefly discussed.

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Reference Code: A76HOG01IDUS

Full Citation: Hogstad, O. 1976. Sexual dimorphism and divergence in winter foraging behaviour of three-toed woodpeckers Picoides tridactylus. Ibis 118(1): 41-50.

Location: ANIMAL EF: PICOIDES TRIDACTYLUS