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Effects of resource availability and distribution on autumn movements of the Nutcracker Nucifraga caryocatactes in the Alps
Author(s) -
ROLANDO ANTONIO,
CARISIO LOREDANA
Publication year - 1999
Publication title -
ibis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.933
H-Index - 80
eISSN - 1474-919X
pISSN - 0019-1019
DOI - 10.1111/j.1474-919x.1999.tb04271.x
Subject(s) - home range , range (aeronautics) , geography , transect , habitat , abundance (ecology) , ecology , larch , forestry , physical geography , biology , materials science , composite material
Radiotracking was used to study the ranging behaviour and movements of the Nutcracker Nucifraga caryocatactes in the Alevé forest (northwest Italian Alps), from September to December 1994‐96, when Nutcrackers collected seeds of Arolla Pines Pinus cembra. Home range size and overlap decreased from September to December. Autumn ranging behaviour was not consistent with territoriality. Nutcrackers stored seeds throughout the Alevé; many apparently stored seeds in scree at high altitudes (above 2200 m) where the forest comes to an end, and also in Larch forests opposite the Alevé (probably to avoid competition with rodents and conspecifics). Estimates of Nutcracker abundance, derived from transect counts, varied significantly among habitats, years and months, which possibly reflected differences in seed availability and abundance. The ranging behaviour observed at the Alevé was compared with that monitored at Mont Avic, another area in the northwest Italian Alps, where resources (in this case Hazel Corylus avellana nuts) were concentrated in a few zones. Home range size was significantly larger at Mont Avic, especially during late autumn. There, the home range size increased and overlap decreased from September to November, when birds abandoned Hazels and dispersed to the coniferous woods. Differences between Alevé and Mont Avic implied that the availability and distribution of resources are the major determinants of the ranging behaviour of the Nutcracker during autumn. However, differences between adults and juveniles were also found.