Tinamou birds: using egg coloration as mating signals

Birds’ coloured plumage and song often serve to signal, attract and recognize mates. Tinamous (order Tinamiformes), which are adapted for camouflage, are not particularly colourful birds. However, the 48 extant species of tinamous produce eggs in an exceptional array of colours.

Researchers in this study proposed that tinamou egg coloration serves as a mating signal for attraction and recognition. To support this hypothesis, they predicted that egg colours coevolved with songs, that the trait was diver-gently adapted to local habitats, and that species sharing habitats and similar song patterns thus should have different egg colours.

They used nest photos from citizen scientists and museum specimen records to quantify egg colouration in RGB color space and acquired song data from a previous study, enabling them to quantify frequency and bandwith in four variables. In order to determine the likelyhood of ancestral sympatry (i.e., species sharing ancestors from the same geographic area), they used GBIF-mediated occurrences sorted to ecoregions.

Through statistical testing the authors found significant associations supporting that egg colouration evolved with song as a sensory-driven trait. They also showed that species with likely ancestral sympatry and similar song patterns tended to have different egg colours. Overall, these findings provided strong support of tinamous using egg colours as mating signals.