Factors affecting movements and home ranges in the jay (Garrulus glandarius)

Abstract

The winter home ranges, movements and density of the jay Garrulus glandarius in the Maremma Natural Park (Tuscany, Italy) are presented, and compared with those already known for the other seasons. The movements of jays were studied for short periods over 6 years by radiotelemetric techniques (26 home ranges), direct observations of movements from vantage points, and transect counts. Summer and autumn ranges were much larger than spring and winter ones. Incremental area plots and auto-overlap analyses showed that, on average, spring ranges increased in area with time without shifting, whereas winter ranges were rather stable. In both periods, however, some birds moved as¯oaters since the degree of range autooverlap decreased signi®cantly with time. In winter and spring, range sizes of jays inhabiting different habitats were signi®cantly different, being larger in sites with higher habitat heterogeneity. The structure of home ranges was variable in all seasons; birds showed jointed and disjointed ranges, with one or more activity centres, in all the possible combinations. In every season the average degree of range overlap between jays caught at the same site was rather high and overall actual overlap, when non-tagged birds were also considered, was even higher. No territorial behaviour was ever observed. During summer jays moved into the pinewood for the greater part of the day to collect cicadas, Cicada orni, and returned to the maquis in the evening. During autumn birds regularly moved within the maquis or from the maquis to the pinewood to cache oak (Quercus ilex) acorns. No regular long movements between habitats were observed during spring and winter. Direct observations and analyses of pellets suggested that food was abundant and highly diversi®ed throughout the year. Thus, seasonal movements and home ranges were¯exible and mainly controlled by food availability and its distribution in space and time.

Acorn dispersal estimated by radio-tracking

“…A slight reduction in acorn dispersal distances occurs between acorns cached in December-January (towards the end of the winter period) and those cached in February-April (beginning of the reproductive period; Table 1). This may be mediated by a reduction in jay territory size towards the reproductive season (Rolando 1998), which suggests a movement of acorns towards the reproductive core area. Consequently, the dispersal distances obtained in this study (especially those corresponding to spring) can be considered to be slight overestimations in comparison with those expected during the natural dispersal period (September-December).…”

“…However, improvements in the methodology may allow tracking acorns even in autumn, i.e., by inter-mixing the marked acorns with the naturally available acorns. This seems advisable as the size of the jay territory decreases towards the reproductive season (Rolando 1998) and some changes in caching behaviour could occur (Clayton 1996).…”

Ranging behavior of the Asian elephant in Sri Lanka

“…However, female #60 who had dependant offspring also had a small range. Therefore additional factors not assessed in this study, such as fine scale variation in habitat productivity and individual variation in habitat and resource exploitation (Rolando 1998), could also be important determinants of home range size. Additionally reproductive status itself, as when mobility of dependant offspring is limited (Belcher and Darrant 2004), and group dynamics, could influence spatial organization and home range size.…”

Post‐fire salvage logging alters a key plant‐animal interaction for forest regeneration

“…Jay selection of live unburnt conifer forest for caching acorns seems to be related to the lower predation risk posed by their own predators, to the suitability of this forest type for breeding (when cached food is more crucial), or to the avoidance of competitors (intra or interspecific) for cached acorns (Andrén 1990, Rolando 1998. Furthermore, jays use visual cues (such as trunks or rocks) to select caching sites that can be memorized for future food recovery (Bennett 1993, Clayton and Krebs 1994, Lanner 1996.…”