Macro-environment (age, sex) and Mega-environment (seasonal and ecological alterations) can affect feather morphology in terms of shapes, colors, and textures. Feather morphology can be dramatically altered due to macro-enviromental changes brought about by life stages and advancing age. Precocial chicks are covered with downy feathers. After molting, adults are cover with contour feathers. Examples shown in (a) Penguin, (b) adult Frigate bird, . (c) young Frigate bird, (d) adult Taiwan country chicken (male, left panel; female, right panel), (e) Wing covert feathers of adult Silver Laced Wyandotte chickens (male, top panel; female bottom panel). Adopted from
Lin et al., (2013), (f) Zebra finches, Taeniopygia guttata, (male, top panel; female bottom panel), (g) Peacocks and peafowls are reknown for their sexually dimorphic feathers displayed during mating season. a,b,c,g, photos by CM Chuong. A, anterior; P, posterior.