Color Differences Among Closely Related Species of Red-Breasted Meadowlarks (Sturnella)

Abstract

Abstract. Interspecific differences in sexually selected traits may be important for maintaining reproductive isolation among closely related species living in sympatry. We present the first study of plumage color differences among males of partially sympatric species of South American red-breasted meadowlarks—the White-browed Blackbird (Sturnella superciliaris), the Pampas Meadowlark (S. defilippii), and the Long-tailed Meadowlark (S. loyca)—using reflectance spectrophotometry and the avian visual model of Vorobyev and Osorio (1998). Reflectance values of sexually dichromatic red plumage patches were measured on study skins. Total reflectance, reflectance in the short wavelength part of the spectrum, and several measures of spectral shape were extracted directly from the spectra. Our analyses revealed that S. loyca and S. defilippii were brighter and had higher reflectance in the short wavelength part of the spectrum than S. superciliaris. Minimum reflectance was located at higher wavelengths in breeding than in nonbreeding plumage. Interspecific distances in avian visual space obtained from the Vorobyev and Osorio (1998) model were considerably higher than the threshold value for color discrimination, indicating that the differences found are also detectable by birds. Taken together, these results show that the red plumage patches of these three species present significant color differences throughout the year, not only in the visible but also in the UV part of the spectrum.

When assumptions on visual system evolution matter: nestling colouration and parental visual performance in birds

“…This methods is currently the most widely used one and is usually justified by supposedly strong phylogenetic inertia of avian visual systems (e.g. Benites et al. , 2007; Eaton, 2007; Avilés et al.…”

Seasonal Changes in Colour: A Comparison of Structural, Melanin- and Carotenoid-Based Plumage Colours

“…Compared to the amount of literature on functional aspects of coloration, only relatively few species and colour patches have been examined in detail for seasonal changes so far [16], [17], [5], [18]–[23]. Most of these studies focused on (presumed) signalling colours and revealed, in general, considerable changes in colour characteristics that might affect signalling through plumage coloration.…”

“…Seasonal changes in plumage coloration are rarely considered of importance for signalling and especially the relevance of signal alteration outside the breeding season has rarely been studied [14] , [15] . Compared to the amount of literature on functional aspects of coloration, only relatively few species and colour patches have been examined in detail for seasonal changes so far [16] , [17] , [5] , [18] – [23] . Most of these studies focused on (presumed) signalling colours and revealed, in general, considerable changes in colour characteristics that might affect signalling through plumage coloration.…”

Plumage and Body Size Differentiation in Blue-Winged Teal and Cinnamon teal

“…Objective measurements of color using reflectance spectrophotometry are necessary, given that birds see plumage colors differently than humans (Cuthill et al, 2000;Vorobyev, 2003;Bennett and Thery, 2007;Hart and Hunt, 2007), including sensitivity to UV reflectance, which is a prevalent aspect of avian plumage (Eaton and Lanyon, 2003). Furthermore, human visual assessment and interpretations of feather coloration might be inadequate, given that models of avian color discrimination suggest human vision often does not see plumage color differences that potentially are visible to birds Eaton, 2005;Hastad et al, 2005;Benites et al, 2007). Hence, we tested for plumage color differences between Blue-winged Teal and Cinnamon Teal from the visual perspective of the birds, for six color patches on males and eight color patches on females.…”