Lekking without color differences: a case of monochromatism in a tropical flycatcher

Lekking birds are often associated with conspicuous plumage and pronounced sexual dichromatism, yet some species exhibit little or no visible differentiation between sexes. We investigated whether the olive-striped flycatcher ( Mionectes galbinus ), a Neotropical lekking tyrannid, exhibits sexual differences in plumage coloration. A total of 48 adult museum specimens of the subspecies Mionectes galbinus heredaceus (18 females and 30 males) from the Vertebrate Collection_Birds (CVA-UV) of the Department of Biology, Universidad del Valle (Cali, Colombia), were analyzed. Reflectance spectra were measured for four body regions, and plumage coloration was evaluated using colorimetric variables and avian visual models. Reflectance spectra showed similar patterns between sexes, with no significant differences in coloration. MANOVA detected no significant sex differences, and modeled chromatic distances remained below 2 JND. These results support functional monochromatism in the studied population of Mionectes galbinus heredaceus and add to growing evidence that lekking species may exhibit limited or absent plumage dichromatism.