Differences in daily singing routines reflect male condition along a montane gradient

Vocal communication is used across taxa to convey a range of information. One of the most well-studied vocal behaviors is the song of temperate passerine birds. Among individuals, male song differs across numerous acoustic parameters, many of which are used by females to assess male quality. Males in better condition often produce higher song output and start singing earlier in the day compared to other males. However, the energetic cost of singing varies throughout the day and may be affected by the singer’s foraging abilities. Along an elevation gradient, harsher environmental conditions at higher elevations shape foraging abilities in mountain chickadees ( Poecile gambeli ), which are non-migratory food hoarders. High-elevation mountain chickadees exhibit superior spatial cognitive abilities and a higher propensity to cache food, which enables them to forage more efficiently, compared to lower elevation birds. High-elevation males may therefore be able to produce higher song output, especially earlier in the day, than low-elevation males. We compared the daily singing routines of male mountain chickadees inhabiting high and low elevations. We found no difference in total daily song output between elevations; however, high-elevation males sang significantly more than low-elevation males at dawn, when singing is both crucial for reproductive opportunities and most costly due to overnight fasting. Song output at dawn may therefore act as an indicator of condition in male mountain chickadees. Significance statement Animals communicate across modalities to exchange information about foraging, predators, and movements. Researchers have studied the vocalizations of songbirds to understand how individual variation affects the behavior of receives, particularly regarding male song and female mating preferences. The song of many songbirds is learned locally and contains information about the location of origin and respective selective pressures. We tested whether natural access to food via food cache recovery was associated with daily singing routines in food-caching birds. Singing at dawn is thought to be costly as it follows overnight fasting. We found that birds from harsher environments—where selection for enhanced spatial cognitive abilities required for cache retrieval is much stronger—sing more at dawn compared to males from milder environments, where selection on spatial cognition is relaxed. This work shows that environmental selection pressures affect signal production in male songbirds, which may provide information to females during mate choice.