June 1999
Las Hoyas, Sierra de Manantlan Biosphere Reserve, Jalisco, México

I am holding a hummingbird that doesn't have the energy reserves to fly away! Hummingbirds
have such a high metabolic rate that they need a constant supply of nectar and insects in order
to fly.  Hummingbirds, like many other species of birds that are omnivorous or carnivorous, vomit
pellets (mostly insectexoskeleton).
Hummingbirds are the only birds that can produce lift from both the upstroke and downstroke
of their wings.  This allows them to hover and the ability to move in all directions.
Some species of hummingbirds in the neotropics are local altitudinal migrants.  That is in the
wintertime they exploit the nectaries of flowers in the warm low lands.  In the spring and summer
they move up to the higher elevations to exploit the nectaries of montane flowers in bloom.  This
behavior allows them to exploit a greater supply of food resources.