Seed size selection in Black-capped Chickadees (Poecile atricapillus)/Selection de tamano de semillas del carbonero cabecinegro (Poecile atricapillus)

Foraging behaviors of animals that promote efficiency can be explained by optimal foraging theory. Previous research suggests that factors associated with nutrition (e.g., oil content) or size (e.g., seed weight and depth) influence the foraging behaviors of Black-capped Chickadees (Poecile atricapillus). In February and March 2020 we examined seed selection in Black-capped Chickadees. Specifically, we collected black oil sunflower seeds discarded from a tube bird feeder by Black-capped Chickadees and compared them with seeds selected at random from the feeder. We measured the depth, length. width, and weight of 180 sunflower seeds. We found that the size and weight of the seeds were both important factors for chickadees in seed selection. In addition, chickadees preferred seeds that were significantly heavier when adjusted for seed size. These findings suggest that Blackcapped Chickadees select seeds based on their size and weight to maximize the nutritional content they intake. Chickadees therefore must also be able to distinguish small differences in seed weight, which may maximize their acquired energy while decreasing the risks of predation when individuals arc exposed during foraging. Received 29 October 2020. Accepted 24 May 2022. Key words: bird feeder, black oil. optimal foraging. sunflower seed. Los comportamientos de forrajeo dc animates que promueven la efkiencia pueden scr explicados por la teoria del forrajeo optimo. Invcstigaeioncs previas sugieren que faetores asociados a la nutricion (ej., contenido de aceites) o tamano (ej.. espesor y peso de las semillas) infiuyen en los comportamientos de forrajeo del carbonero cabecinegro (Poecile atricapillus). En febrero y marzo del 2020 examinamos la seleccion de semillas del carbonero cabecinegro. Especificamentc. colectamos semillas de girasol de aceite negro descartadas de un eomedero de tubo para aves por el carbonero cabecinegro y las comparamos con semillas selcccionadas al azar del eomedero. Medimos el espesor, largo, ancho y peso dc 180 semillas de girasol. Encontramos que el tamano y el peso de las semillas eran faetores importantes para los carboneros al seleceionar las semillas. Adcmas. los carboneros prefirieron semillas que eran significativamente mas pesadas al ajustar las medidas por tamano de semilla. Estos hallazgos sugieren que los carboneros cabecinegros seleecionan las semillas con base en el tamano y el peso para maximizar el contenido nutrieional que ingieren. Los earboneros deben entonees podcr distinguir pequenas difereneias de peso de las semillas, lo que podria maximizar su energia adquirida y a la vez disminuiria los riesgos de depredation a los que se sometcn los individuos durante el forrajeo. Palabras clave: aeeite negro, eomedero de aves. forrajeo Optimo, semilla de girasol.
Optimal foraging theory aims to understand the foraging behavior of animals by measuring proxies of foraging efficiency, which can be used to estimate the fitness of the animal (MacArthur and [...]