Hummingbirds
feed on copious quantities of nectar. When, for example, a
Broad-tailed or Rufous Hummingbird is subsisting on the
nectar of scarlet gilias in subalpine areas of Colorado, it
must take in more than its normal body water content every
day in order to get enough sugar to fuel its metabolism. (It
gets fats and protein by also feeding on small insects.) Its
kidneys must work very effectively to retain needed body
salts while removing the excess water that floods them after
sugar is absorbed from the nectar. In spite of their small
size, and thus natural susceptibility to evaporative loss of
water (since they have a huge area relative to their
volume), small hummingbirds in the laboratory fed on
synthetic gilia nectar produced urine and cloacal fluid (the
latter being water passed directly through the gut)
amounting to 75-85 percent of their body weight daily. That
is the rough equivalent of a human adult voiding 20 gallons
of water a day! SEE: Determining
Diets;
Hummingbird
Foraging Bouts;
Optimally
Foraging Hummers;
Diet
and Nutrition. Copyright
® 1988 by Paul R. Ehrlich, David S. Dobkin, and Darryl
Wheye.