| Hummingbirds are
the smallest homeotherms, they suffer from low thermal inertia and high
heat loss. As a result of this, convective cooling due to wing and
air movements further impedes thermoregulation in humming birds.
When temperature is lowered, the wingbeat kinematics of hummingbirds change.
Their frequency is increased, but the stroke amplitude decreases, this
suggests there is a thermoregulatory role in Hummingbird flight muscles
(Chai et al. 1998). Research has shown that in hover feeding, oxygen
consumption increases moderately between 35-5 degrees Celsius, but while
perch feeding, it increases dramatically. These results suggest that
heat from the contraction of flight muscles substitutes for regulatory
thermogenesis (Chai et al. 1997).