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

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Abstract
Although age-specific habitat use has received much attention in recent years, the mechanisms that underlie ecological separation are not well known. This study examined the age-specific feeding site selection and its ecological mechanism in free-ranging Rock doves (Columba livia; referred to as pigeons). The distribution of age-classes at the feeding sites adjusted to a partially truncated distribution as follows: adults were consistently found more often than expected in the most rewarding feeding site, while juveniles were more often found in suboptimal sites. A removal experiment was conducted to determine whether competition accounted for the niche segregation between juvenile and adult pigeons. The reduction in intraspecific competition following removal was accompanied by an increased use of the preferred feeding site by juveniles. However, when the population recovered its initial size through immigration, juveniles were once again more frequently found in the suboptimal site. The proportion of juveniles feeding in each site was related to the total number of birds present; the higher the total number of birds, the higher the percentage of juveniles feeding in the less preferred site. These results support the idea that segregation between age-classes is due to competition by which adults displace juveniles from the richer foraging sites.