Climatic Patterns Predict the Elaboration of Song Displays in Mockingbirds

Climatic variability and unpredictability [1] affect the distribution and abundance of resources and the timing and duration of breeding opportunities. In vertebrates, climatic variability selects for enhanced cognition when organisms compensate for environmental changes through learning and innovation [2-5]. This hypothesis is supported by larger brain sizes [6], higher foraging innovation rates [7-9], higher reproductive flexibility [10-12], and higher sociality [13] in species living in more variable climates. Male songbirds sing to attract females and repel rivals [14]. Given the reliance of these displays on learning and innovation, we hypothesized that they could also be affected by climatic patterns. Here we show that in the mockingbird family (Aves: Mimidae), species subject to more variable and unpredictable climates have more elaborate song displays. We discuss two potential mechanisms for this result, both of which acknowledge that the complexity of song displays is largely driven by sexual selection [15, 16]. First, stronger selection in more variable and unpredictable climates could lead to the elaboration of signals of quality [14, 17-20]. Alternatively, selection for enhanced learning and innovation in more variable and unpredictable climates might lead to the evolution of signals of intelligence in the context of mate attraction [14, 21-23].