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1. Respiratory System
The respiratory system in lovebirds serves to transfer oxygen from
the air to the bloodstream. Lovebirds breathe air in through their
nostrils and mouth. The air travels to the lungs, where the
bloodstream absorbs the oxygen.
Unlike mammals, birds lack sweat glands and cannot cool themselves
by perspiring. Instead, lovebirds have thin-walled pouches called
air sacs between various organs of the body. The sacs are connected
to the lungs. As a lovebird inhales air, some of it passes from the
lungs into the air sacs. This air cools the organs and prevents them
from overheating.
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2. Digestive System
Lovebirds do not have any teeth and therefore chew their food. They
must either cut it up with their bill or swallow it whole.
From the mouth, food passes into the esophagus, a tube like organ
with expandable walls. In lovebirds, the esophagus has a bag-like
swelling called a crop. Birds can store food in the crop until there
is room for it in the stomach. Birds also store food in the crop to
carry to their babies.
Food passes from a lovebird's esophagus or crop into the stomach. In
lovebirds, the stomach has two parts. In the first part of the
stomach, digestive juices are added to the food. The second part of
the stomach, which is called the gizzard, has thick, muscular walls
that grind food. The gizzard secretes a keratin-like fluid which
hardens around the food and aids in grinding any hard food.
After, food passes from the stomach into the small intestine, where
the nutritious matter is absorbed into the blood. The remaining
waste matter moves into the large intestine. Nearly all or most of
the water in the wastes is absorbed by the wall of the intestine.
Wastes pass out of an opening at the rear of the lovebird's body
called the vent.
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3. Circulatory System
The circulatory system distributes blood throughout a lovebird's
body. The system consists of the heart and blood vessels. The heart
of lovebirds beats much faster than the heart of a human, at
approximately 200-300 times a minute. Arteries carry blood from the
bird's heart to other parts of the body. The blood returns to the
heart through the bird's veins.
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4. Nervous System
The nervous system of a lovebird is similar to that of other
vertebrates. It consists basically of the brain and nerves. The
nerves carry messages from the senses to the brain and from the
brain to the muscles.
A bird's brain is small compared with a mammal's, but the lower part
of the brain, the cerebellum, is relatively larger in birds than in
mammals. The cerebellum is the part of the brain that regulates
balance and movement, and coordinates the muscles that lovebirds use
to fly.
The upper part of the brain, the cerebrum, is the part of the brain
that controls learning. Some parrots, including lovebirds, have a
bigger cerebrum than other birds, such as sparrows. This explains
why parrots can learn how to talk and do tricks.
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5. Reproductive System
The male sex organs in vertebrates are called testes, and the female
organs are called ovaries. The testes and ovaries produce sex cells,
or sperm and eggs. In birds, the testes lie inside the body, just
beneath the backbone. At the start of the breeding season, the
testes grow larger in males, and a female's eggs start to enlarge
and accumulate yolk. When an egg reaches a certain stage of
development, it passes from the ovary into a tube-shaped organ
called the oviduct. About this time, mating takes place.
Most birds mate by pressing their vents together. Sperm cells
quickly pass from the male's vent into the female's. One or more
sperm cells may unite with one or more egg cells in the oviduct.
This union produces a fertilized egg, or zygote.
The zygote, which is on the surface of the yolk, continues down the
oviduct. Glands in the middle part of the oviduct deposit albumen
(egg white) around the yolk. Glands in the lower part produce the
shell around the albumen. The egg is then laid, and the zygote
develops into an embryo as the egg is incubated. The yolk and
albumen provide food for the embryo.
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