WFC 111 Lecture 17: Lecture 17- 10/31
11 Nov 2016
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Document Summary
Takes >1 hour for hummer to (cid:364)wake-up(cid:365) They lose most of their heat out of their legs. Avoid heat loss by keeping heat closer to the core. Problem for large birds (lower surface: volume ratio) Expose apteria (surface of wing, erect feathers) & orient to sun. Toucans big bill is for heat loss (large surface) Deal with heat gain by evaporative cooling. E. g. evaporative water loss in brown towhee increased 4x when ta30 to 40oc. Water loss (% of body mass/day) will decrease with body size (surface: volume ratio) Because birds have high metabolism, produce more metabolic. Water needs of many species met fully by diet alone. Seed eaters especially require source of water. Birds and reptiles excrete as uric acid. Can increase concentration in cloaca up to 3000x uric acid in blood. Avian kidneys great at concentrating nitrogenous wastes, but . Cannot concentrate salt or electrolytes above blood level. To flush kidneys of salt requires water!
