Learning about Hummingbirds

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 who'se downward curving bill allows it to
draw nectar from heliconias. 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.




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