Variation in plumage reflectance but not song reflects spatial cognitive performance in black-capped chickadees (Poecile atricapillus)

In seasonally variable environments, enhanced cognitive abilities may allow animals to adjust their behavior to changing conditions. Nonmigratory food-caching birds, like chickadees, rely on specialized spatial cognition to successfully cache and retrieve food items and survive the winter. Previous studies have linked spatial cognitive performance in chickadees to enhanced fitness, including survival and reproduction; however, it remains unknown whether females assess male cognitive ability via direct observation or secondary sexual traits. In this study, we investigated whether variation in common secondary sexual traits of songbirds, song and plumage, serve as indicators of cognitive ability in black-capped chickadees (Poecile atricapillus) when accounting for dominance rank. To explore this, we brought wild male black-capped chickadees into captivity, tested their performance in three spatial cognitive abilities (spatial learning, cognitive flexibility, and long-term retention), determined the relative social dominance ranks among all individuals, measured plumage reflectance in six body regions, and recorded their fee-bee songs to assess the relationship between these variables. Our findings show that birds with brighter white plumage and greater contrast between black and white plumage patches showed better spatial learning and memory performance. In contrast, we found no significant associations between cognitive performance and song variation. Our results suggest that females may use some secondary sexual traits as signals for cognitive performance, although, we suggest direct observation may also be important for mate choice involving cognitive ability in chickadees. This work provides insights into female mating decisions, highlighting the complex nature of sexual selection and female preferences.