Non-Territorial Behaviour and Habitat Selection in the Jay Garrulus glandarius in a Mediterranean Coastal Area during the Reproductive Period

Abstract

Spring territorial behaviour and habitat selection of the Jay Garrulus glandarius were investigated in two study areas in the Maremma Natural Park (Central Italy). Seven birds in 1990 and seven in 1991 were trapped and subsequently radio-tracked. Incremental area plots and the analysis of auto-overlap showed that most of the Jays did not have fixed home ranges, and that these overlapped greatly. Furthermore, many untagged Jays were seen inside the home ranges of the tagged ones and one pair of Jays successfully reproduced in 1991 inside other Jays' home ranges. No aggressive interactions were observed. These data seem to suggest that the Jays in Maremma do not show territorial behaviour. Home range sizes at one study area (Faunistico) were larger than in the other area (Pratini) (on average 36 ha versus 5 ha). This could depend on the higher habitat diversity or lower habitat quality of the first area. Habitat use differed between the areas. At Pratini the maquis scrub was positively selected whereas the olive grove was avoided; at Faunistico the maquis, the olive grove and the cultivated fields were avoided whereas the meadows with scattered trees and the open scrub were positively selected. The non-territorial behaviour of the Jays in the Maremma Natural Park may be determined by several local factors, such as resource abundance, high density of birds, low reproductive rates and food partly being collected outside the maquis. In particular, both in the case of resource abundance and in that of high density of birds, the cost of sharing resources would be less than the cost of defending the territory against all intruders and a non-territorial system would indeed be expected.