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Résumé :
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To study correlation between the presence of fleshy fruits and frugivorous birds, standardised mappings of fruits and birds were performed on three areas (hedges, flood plane, forest; 50 ha each) in northern Hesse. The mappings were performed between 01.06.1997 and 31.12.1999 two to three times during a month.Between March and July fleshy fruits were extremely rare. The number of fruiting species and the total fruit mass increased in August and reached maximum values in September and October. Fruits were most abundant and diverse on the area with hedges (up to ca. 9000 kg total fruit mass per 100 ha and 19 synchronously fruiting species). Less fruits could be found in the flood plane area and least on the forest area.The hedges area was also the richest in frugivorous bird species and bird individuals, followed by the flood plane and the forest. On all areas, bird diversity was highest in late spring and summer (up to 14 species on the hedges area), lowest in winter (up to 2 species in the forest area). Concerning the number of bird individuals, typical patterns of habitat use could be found: In summer, the bird numbers were similar on all three areas. During the late summer and the autumn the numbers drastically rose on the hedges area, but sank on the forest area. On the flood plane, the phenological pattern was similar to the one on the hedges area, but total bird numbers were much lower. Non-frugivorous birds did not show a preference for the hedges area in autumn.An analysis of the habitat use of some of the most abundant frugivorous birds on a smaller level showed that these birds preferred places (100 m x 100 m squares), where preferred fruits were present. The Garden Warbler (Sylvia borin) and the Blackcap (Sylvia atricapilla) significantly preferred places with ripe elder (Sambucus nigra) fruits. Blackbirds (Turdus merula) and Redwings (Turdus iliacus) preferred places with hawthorn (Crataegus monogyna) fruits in autumn. Blackbirds preferred places with fruits of Rosa species in winter. However, it could also be shown that these bird species often prefer the same places in spring, when no fruits are ripe. Based on these results, it is suggested that fruits are one parameter for the habitat use of frugivorous birds in autumn and winter but not the only important parameter. Fruits may be the most important parameter in habitat use during times when the ground is frozen and/or snow covered during the winter.
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