Learning about Hummingbirds
by Brian Ramsey
Hummingbirds are a joy for a birdwatcher to observe. They are found only
in the Western Hemisphere, from as far north as Southeastern Alaska and
the Maritimes of Canada and as far south as Southern Chile. There are
approximately 350 species of hummingbirds with 320 species found in the
tropics. Within the family of hummingbirds is found the smallest bird in
the world, the Bee Hummingbird of Cuba at 2.17 inches (5.5 cm) and weight
1.95gm (0.07 oz). Hummingbirds range in size from 2 inches to 8 inches.
The hummingbird derives its name from the humming sound that is produced
by its rapid wingbeat. Generally the wingbeat is so rapid that the
individual only sees a blur as most of these birds flap their wings about
50 times per second. The speed of the wingbeat depends on the size of the
bird, the largest the Giant Hummingbird, has a wingbeat rate of 10-15
times per second. The fastest recorded rate was about 80 times per second,
on a tiny Amethyst Woodstar, and the slightly smaller Bee Hummingbird -
the world's smallest bird - may have an even faster rate. A hummingbird's
wing is flexible at the shoulder, but inflexible at the wrist, this
enables them to fly in many different directions. They can fly right,
left, up, down, backwards and even upside down. To move away from the
flowers on which they feed hummingbirds fly backwards and are the only
bird able to fly backwards. While other birds get their flight power from
the downstroke only, hummingbirds also have strength on the up-stroke.
Though they fly very fast, they can suddenly stop and make a soft landing.
They are so light they do not build up much momentum. Hummingbirds have
poorly developed feet, so that although they are able to perch and will do
so when feeding or resting, they do not walk. In order to move, even along
a branch, they fly. Hummingbirds lift from perches without pushing off;
they rise entirely on their own power, flapping their wings at almost full
speed before lifting off. Hummingbirds sleep perched on branches with
their neck retracted and their head forward, the bill pointed up at a
sharp angle, and the feathers fluffed.
It is believed that hummingbirds live for only 3 to 4 years. They have a
fast heartbeat with a rate of 1260 beats per minute having been measured
in a Blue-throated Hummingbird. In torpid hummingbirds, the heart rate can
drop to 50-180 per minute. Their fast heart rate and rapid wing motion
require them to feed regularly throughout the day. It is reported that
they must feed every 10 minutes and they may consume 2/3 of their body
weight in a single day. A major part of a hummingbird's diet is the nectar
they obtain from flowers and their bills are perfectly adapted to the
various types of flowers that they feed on. Some hummingbirds have
especially curved or elongated bills that allow them to feed on special
flowers, eg the White-tipped Sicklebill hummingbird whose downward curving
bill allows it to draw nectar from heliconias. The Ruby-Topaz Hummingbird
has a short and slightly decurved bill that is suited to feeding on the
flowers of the ixora shrub. The Blue-tailed Emerald has a short bill that
is suited for feeding on the Hibiscus flower. the Copper-rumped
Hummingbird has a straight long bill that allows it to feed on medium
sized tube shaped flowers such as the allamanda. In feeding, hummingbirds
use their tongue to lap the nectar in a similar manner to cats lapping
milk. Their tongue can extend a distance equal to their beak length. As
they feed hummingbirds accidentally collect pollen and as they move from
flower to flower, they help the flowers to reproduce.
Hummingbirds have little or no sense of smell, so colour is important to a
hummingbird's search process for locating flowers containing nectar. While
they will visit any flower that has sufficient nectar they prefer flowers
that are red to orange in colour. It is believed that there are several
reasons for this colour preference. Red flowers standout in a green
background and so are more easily seen by the hummingbird. It is also
believed that because hummingbirds compete with insects for nectar they
choose flowers that are less likely to be visited by insects. Most insects
do not see well at the red end of the colour spectrum and so may not visit
red flowers while hummingbirds see the full visible spectrum.
Hummingbirds also need protein in order to build muscles, so they eat
insects. They prefer to feed on small spiders and slow-flying insects such
as gnats, small wasps and leafhoppers, which are rather buoyant in air and
easy to catch. They also probe the bark and foliage for insects such as
aphids, spiders, caterpillars and insect eggs. It is believed that up to
one-half of their diet is made up of small insects. Hummingbirds are
capable of living for extended periods without nectar as a component of
their diet. They can quickly convert fat reserves and recently ingested
insects to energy when deprived of nectar. Hummingbirds compete for nectar
and insects and so they develop territories, which they guard
aggressively. They will fight with other hummingbirds that enter their
territory but serious harm is seldom inflicted during these fights. Also
when food sources are scarce they fight to protect their source.
Most hummingbirds are green except hermits, which are mainly brown, and
are known for the iridescence. These brilliant, iridescent colors of the
hummingbird plumage are caused by the refraction of incident light by the
structures of certain feathers. These structures split light into its
component colors, and only certain frequencies are refracted back to the
viewer. The brown colour in some hummingbirds is the result however of
pigmentation. Hummingbirds groom themselves with their bills and claws,
using oil from a gland near their tail. They also use their claws like a
comb to groom their heads and necks. They sunbathe positioning their
breast towards the sun and fluffing out, extending their neck and
spreading their tail. Hummingbirds also take water baths using the water
in shallow pools or cupped leaves. They flutter their wings or pull them
straight back while lifting and spreading their tail; they dip their chins
and bellies into the water. At times they can be seen sitting on a bare
branch allowing the rain to soak through to their skin. After bathing they
will preen and dry their feathers.
Hummingbirds build cup shaped nests, however hermits build long hanging
nests usually attached to foliage. Male hummingbirds do not contribute to
the building of nests or the care of young. All feeding is therefore left
to the female. When feeding the female perches on the side of the nest,
arches her back, stretches her neck, lifts her head, and holds her bill
down to regurgitate nectar and half-digested insects to her babies. Her
throat swells and she pumps her beak like a sewing needle.
Although various larger birds, snakes, and mammals raid hummingbird nests
for eggs and chicks, this is not a major cause of death.
About the Author
Brian Ramsey, who is an avid birdwatcher and amateur photographer is the
author of the bird identification CD, Discovering the Birds of Trinidad
and Tobago found at www.birdsoftt.com
that provides photographs and information on birds of
tropical rainforests and other
tropical habitat. |
