An Anhinga slowly unfolding its wings on a cloudy afternoon as the sun peeps out for a moment or two.
I always assumed that Anhingas spread their wings to dry them. But recently, someone told me they spread their wings to gather the warmth of the sun's rays.
Per Google, maybe both answers are correct i.e. "Thus, it appears that Anhingas adopt a spread-wing posture primarily for thermoregulation -- to absorb solar energy to supplement their low metabolic heat production and to offset partly their inordinately high rate of heat loss due to convection and (when wet) evaporation from their plumage."