Plumage coloration plays a crucial role in ecology, often reflecting adaptive responses to environmental heterogeneity. According to Gloger’s rule, animals in warm and humid regions are expected to exhibit darker coloration; however, the White Eared Pheasant ( Crossoptilon crossoptilon ), a nationally protected and endemic species in China, presents an exception. This species exhibits striking plumage polymorphism, with populations displaying either white or grey morphs. To explore the ecological basis of this divergence, we combined satellite tracking data with dynamic Brownian Bridge Movement Models (dBBMM), principal component analysis (PCA), and maximum entropy modeling (MaxEnt) to compare differences in home range size, habitat composition, and climatic as well as vegetation characteristics between the two morphs. Our results showed that the white morph occupied smaller home ranges with higher forest cover and longer-lasting snow. In contrast, the grey morph exhibited significantly larger winter and spring home ranges, with a higher proportion of grassland and shrubland, suggesting lower food availability and greater predation risk in more open habitats. Environmental niche models further indicated that the white morph was more common in lower-elevation, warmer, and wetter environments, whereas the grey morph predominated in colder, drier, higher-elevation regions with stronger solar radiation. These patterns suggest that plumage divergence reflects adaptive responses to differences in snow cover duration, vegetation structure, and background coloration. From a mechanistic perspective, the divergence between morphs may be linked to differences in melanin deposition, which is associated with the melanocortin system and may influence a suite of correlated physiological and behavioral traits, such as stress resistance and habitat use. Our findings not only provide novel evidence for exceptions to Gloger’s rule but also highlight the importance of environmental heterogeneity in driving phenotypic differentiation in montane pheasants of the Qinghai-Tibetan Plateau. Recognizing such ecological differentiation among color morphs may also have important conservation implications, suggesting that habitat heterogeneity and seasonal snow dynamics should be considered in management strategies for alpine Galliformes.
Cheng et al. (Wed,) studied this question.