Frequency distribution and environmental correlates of plumage polymorphism in the grey fantailRhipidura fuliginosa

Abstract

The grey fantail (Rhipidura fuliginosa)in New Zealand displays a striking plumage polymorphism. Some individuals are coloured almost entirely black (the "black morph"), while other individuals sport a contrasting brown and white plumage (the "pied morph"). The adaptive significance of plumage polymorphism in this species is unknown. We mapped the relative distribution and frequency of each morph across the entire South Island range of the fantail, and correlated the frequency of the morphs with a variety of ecological variables. The black morph comprised <5% of individuals across the South Island and, contrary to previous observations, was least frequent at the southern extremes of its range. From historical records, the frequency of the black morph also appears to have declined, although we cannot rule out a bias in reporting rates of the black morph in the literature. The relative frequency of the two morphs was not related to vegetation type, annual rainfall, altitude, or mean annual temperature. Although we could not identify an environmental variable that might explain the distribution of the two morphs over the South Island, changes in the relative abundance of each morph suggest a dynamic process that warrants further long-term study.

Clinal variation in the morph ratio of Black Sparrowhawks Accipiter melanoleucus in South Africa and its correlation with environmental variables

“…These patterns have been viewed as implying that there is an important selective advantage for the colour morphs or the genes associated with different morphs in the different areas (O'Donald ). For bird species, the adaptive significance of different morphs is poorly understood, although a few studies have demonstrated links between these clines and potential drivers such as environmental variables (Wunderle ), whereas others have failed to find any such relationships (Galeotti & Cesaris , Atkinson & Briskie ). Identifying the environmental patterns associated with these ratio‐clines may therefore be useful for indicating the selective forces operating on the balancing mechanisms of the different morphs (Galeotti et al .…”

Egg color polymorphism and morph-ratio variation in Korean populations of the Vinous-throated Parrotbill

“…Interestingly, we found a morph-ratio cline in egg color ratios; that is, the proportion of white eggs in a population dramatically decreased at lower latitudes. Morph-ratio clines have been observed frequently in birds with polymorphic appearances (Wunderle, 1981;Atkinson and Briskie, 2007) but no such cases have been reported with repect to egg colors. Our results are therefore the first showing the presence of a morph-ratio cline in polymorphic egg colors of birds.…”