Movement ecology of the Sacred ibis (Threskiornis aethiopicus) outside of its natural range

Understanding the movements of alien species in newly colonized territories is crucial for addressing the challenges posed by global transformations and threats to biodiversity conservation. In this study, we used mark-resight data to investigate the dispersal movements of the sacred ibis in Italy, which were virtually unknown until now. We analyzed data from 357 colour-ringed ibises, the majority of which were marked as nestlings, including six hybrids with the African spoonbill. Resightings revealed a tendency towards philopatry, with most observations occurring within 10 km of the original colony. However, some individuals traveled much farther, with maximum recorded distances exceeding 300 km from the ringing site. The average long-distance travel speed was 15.4 km per day. Movement directions showed clustering along both the North-South and East-West axes, influenced by colony location. Landfills emerged as significant feeding sites, particularly in winter. Age class had a significant negative effect on dispersal distance, whereas timing of hatching showed a positive effect. Despite the apparent pronounced tendency towards philopatry, the high dispersal potential of the sacred ibis suggests the possibility of rapid territory expansion and colonization of areas far from natal colonies. These findings provide the first evidence of the dispersal capability of the sacred ibis outside its natural range and should be used to inform management actions aimed at mitigating the potential effects of this invasive species.