Do museum specimens accurately represent wild birds? A case study of carotenoid, melanin, and structural colours in long-tailed manakins Chiroxiphia linearis

Museum specimens continue to be an invaluable resource for taxonomic, systematic, and comparative studies, and are increasingly relied upon for novel research purposes. Evaluating variation in the colour of avian study skins forms the basis for a broad range of research questions, yet few studies have investigated whether the plumage colouration of museum specimens accurately reflects colouration in wild birds. In this study, we use reflectance spectrometry to compare the plumage reflectance of avian museum skins and wild birds. We use long-tailed manakins Chiroxiphia linearis, to investigate these potential differences in colour. Long-tailed manakins are ideal for this type of study as their colourful plumage patches result from three primary plumage colouration mechanisms found in birds: melanin pigmentation, carotenoid pigmentation, and structural colouration. These features of their plumage allowed us to independently assess variation in each plumage colouration mechanism. Reflectance spectra obtained from museum specimens were very similar to those obtained from wild birds, and the colouration of specimens was usually well within the range of variation observed in wild birds. As such, museum specimens can accurately represent the colouration of wild birds. Nevertheless, we found significant differences in colouration between museum skins and wild birds. We documented differences in brightness, hue, saturation, and chroma, although the direction and magnitude of these differences varied by mechanism of colouration. Multivariate analyses revealed that the age of museum specimens and the time of year at which they were collected contributed to some of these differences. We discuss potential proximate causes of these changes in colour, many of which apply to both museum specimens and wild birds, and identify the types of studies that are likely to be most sensitive to these changes.