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 Black-capped 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 are exposed during foraging.

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