Age-related feeding site selection in urban pigeons (Columba livia): experimental evidence of the competition hypothesis

Although age-specific habitat use has received much attention in recent yea rs, the mechanisms that underlie ecological separation are not well known. This study examined the age-specific feeding site selection and its ecologi cal mechanism in free-ranging Rock doves (Columba livia; referred to as pig eons). The distribution of age-classes at the feeding sites adjusted to a p artially truncated distribution as follows: adults were consistently found more often than expected in the most rewarding feeding site, while juvenile s were more often found in suboptimal sites. A removal experiment was condu cted to determine whether competition accounted for the niche segregation b etween juvenile and adult pigeons. The reduction in intraspecific competiti on following removal was accompanied by an increased use of the preferred f eeding site by juveniles. However, when the population recovered its initia l size through immigration, juveniles were once again more frequently found in the suboptimal site. The proportion of juveniles feeding in each site w as related to the total number of birds present; the higher the total numbe r of birds, the higher the percentage of juveniles feeding in the less pref erred site. These results support the idea that segregation between age-cla sses is due to competition by which adults displace juveniles from the rich er foraging sites.