Limited winter constraints in a recent translocated endangered island bird

Abstract

Translocation programs are vital conservation tools for endangered species with restricted and isolated populations. Assessing the establishment phase is crucial to understand how translocated individuals adapt to new environments and overcome ecological constraints, especially during winter, the most challenging period of the annual cycle. This study focused on the endangered Gran Canaria blue chaffinch (Fringilla polatzeki), an endemic woodland bird species with a highly restricted natural range. Nine years after initiating a translocation program to a new pine forest (La Cumbre), we examined the blue chaffinch’s winter biology during its establishment phase, assessing how limiting the winter season could be in this new habitat, by investigating dependence on supplementary feeding and the intensity of competitive interactions. Our findings reveal minimal reliance on supplementary feeding, unaffected by temperature, with chaffinches allocating only 5.2% of their daily time to feeders, primarily in the afternoon. The species demonstrated competitive dominance over other seed-eating birds unique to La Cumbre, suggesting that interspecific competition does not constrain resource access. Additionally, intraspecific competition was minimal, with few aggressive interactions and no differences in feeder access related to sex or age within the dominance hierarchy. These results indicate that La Cumbre’s winter conditions do not significantly limit the blue chaffinch foraging activities during the critical establishment phase. Combined with prior evidence of comparable physical condition, reproductive success, and genetic variability between translocated and natural populations, our study supports La Cumbre as a suitable translocation area. This research highlights the importance of ecological assessments beyond the breeding season to ensure the long-term success and persistence of translocated populations.