The North American beaver Castor canadensis is an invasive species in the Tierra del Fuego Archipelago. Due to this biological invasion, Argentina and Chile signed an agreement to restore affected ecosystems by eradicating beavers. In southern Patagonia, the beavers’ ecological impacts are well studied, but there is a relative lack of information on how their invasion (and potential removal) could affect bird communities. In the southern portion of Tierra del Fuego's ‘big island’ (Isla Grande), we conducted passive acoustic monitoring and avian point counts in intact riparian forests, beaver ponds and beaver meadows (i.e. drained ponds) to assess spatial and seasonal differences in acoustic activity and avian abundance, species diversity and functional diversity. During spring and summer, acoustic activity was significantly higher in meadows than in forests, with ponds exhibiting intermediate values. Abundance and species diversity exhibited similar patterns, driven largely by resident passerines, while functional diversity tended to be highest in ponds, largely due to ducks and raptors. Effects were weaker in fall and winter. Acoustic metrics exhibited moderate to strong correlations with all point‐count‐derived metrics. Synthesis and applications. At the patch level, the avian community was more abundant and diverse in beaver‐modified habitats than in intact riparian forests, though communities in modified patches may not differ substantially from those in analogous natural open and wetland habitats. Dam breaching and pond drainage did not yield a return to an intact forest bird community, indicating that active reforestation may be necessary to restore avian communities to pre‐beaver conditions in the short to medium term, as sought by the binational agreement. Given the immense challenges of eradication and restoration, its social‐ecological costs and benefits—including those related to avifauna—should be thoroughly considered in establishing goals or indicators of success.

Dieta de la lechuza de campanario (Tyto alba) en Ocoyoacac, Estado de México Diet of the Barn Owl (Tyto alba) in Ocoyoacac, Estado de MexicoAlvaro González-Calderón* ResumenEstudié los hábitos alimenticios de la lechuza de campanario (Tyto alba Strigiformes) en el municipio de Ocoyoacac (Estado de Méxi-co) en 2012. Describí la dieta de esta rapaz a partir del análisis de los restos no digeridos de 732 egagrópilas colectadas. Empleé los índices de riqueza, dominancia y diversidad de Margalef, Simpson, Shannon-Wiener y Pielou, obtuve la diversidad de presas consumidas. Mediante el índice de nicho trófico de Levins estandarizado evalué la amplitud trófica de esta rapaz y estimé la corre lación entre las dimensiones de las egagrópilas con el número de presas consumidas. Los mamíferos pequeños representaron la categoría con mayor frecuencia de depredación, seguida de artrópodos y aves. La dominancia de mamíferos pequeños resultó relativamente baja (λ = 0.20). La especie con mayor frecuencia de consumo fue Rattus rattus, seguida de cuatro especies de roedores con una frecuencia de consumo abundante (Microtus mexicanus, Reithrodontomys microdon, R. megalotis y Peromyscus maniculatus). El valor del índice Shannon-Wiener (H' = 1.85), y del índice de nicho trófico de Levins estandarizado (Bst = 0.42) mostraron una uniformidad relativamente baja y tendencia selectiva en el consumo de mamíferos pequeños. En la dieta de esta rapaz fue relevante el consumo de artrópodos en los que se incluyeron arácnidos. Así mismo observé selectividad en el consumo de aves. Las correlaciones significativas entre las dimensiones de las egagrópilas con el número de presas consumidas fueron discutidas. Los resultados sugieren que la lechuza de campanario tiene un papel importante en el control biológico de roedores exóticos y nativos de la región.Palabras clave: Depredador-presa, control biológico, nicho trófico, Tyto alba, área urbana. AbstractI studied the feeding habits of the Barn Owl (Tyto alba Strigiformes) in Ocoyoacac, State of Mexico (Mexico) in 2012. On such occasion, its diet was analyzed based on the description of the mass of undigested parts of preys in 732 pellets collected. For such description I resorted to Margalef, Simpson, Shannon-Wiener and Pielou diversity index showing the diversity of preys on which the Barn Owls fed. Based on Levin's standardized trophic niche index the food niche breadth was estimated as well as the correlation between pellet dimensions and the number of eaten preys. Small mammals were the most frequent source of food, followed by arthropods and birds. The dominance of small mammals was relatively low (λ = 0.20). Rattus rattus was the species most frequently consumed, followed by four other rodent species associated with an abundant frequency of consumption (Microtus mexicanus, Reithrodontomys microdon, R. megalotis and Peromyscus maniculatus). Shannon-Wiener index value (H' = 1.85) and Levin's standardized trophic breadth index (Bst = 0.42) showed a relatively low uniformity and a selective tendency i...

No abstract