Perching Mechanism of Birds

Good Morning Readers, hope your morning is good and you are doing great. Today, we will see, how birds fly and what is the reason behind this mechanism. So, let's start and make this article simple and short.

In flying birds the muscles of the leg are so modified that they can sit or perch on branches holding them tightly by their flexible toes. The muscles responsible for this mechanism are called perching muscles. There are two sets of these muscles:

1. Flexor

2. Extensor

Flexor Muscles

There are eight flexor muscles situated on the back of tibiotarsus and are attached to the knee. Six of these muscles are connected with the second, third and fourth anterior toes and the remaining two are connected with the hallux (the first toe). Tendons from these muscles are attached to the phalanges of the toes on their ventral surface. Since these muscles cause flexion of the toes they are called flexor muscles. The chief flexor muscles are peroneus medius and flexor perforans which are attached to the tibiotarsus. The tendon of the peroneus muscle passes along the back of the ankle joint and then divides into three, each of which goes to the ventral side of the three forwardly directed toes. The tendon of the flexor perforans goes to the backwardly directed hallux (first toe). The two muscles are joined together by a slip, so that a pull on any tendon flexes the toes. The calf muscle or the gastro-cnemius is present on the anterior side of the crus. Its tendon joins the tendons of the peroneus muscle and thus helps in perching. In many birds there is a small muscle called ambiens muscle which arises from the pectineal process of the ilium and passes over to the outer surface of the tibiotarsus. Its tendon joins the tendons going to the front digits. The function of the ambiens muscle in perching is negligible and it can be severed without affecting the perching ability.

Extensor Muscles

To unlock and release the feet from the perch the bird has to raise its body to straighten the legs. The opening of the toes is affected by the tibialis anterior muscle which is present on the anterior aspect of the tibiotarsus. Branches of its tendon go to the upper surface of the anterior toes. When the bird raises its body, the extensor muscle is contracted and the toes get open.

Mechanism

When the bird settles on the branch of a tree, the legs are bent at the knee and the ankle. As a result the flexor tendons become stretched exerting a pull on the toes which thus become automatically flexed and grip the perch tightly. When the bird sleeps on a perch, the weight of the body bends the ankle more and the grip on the perch becomes tighter. A nerve centre on the plantar surface of the toes initiates the grip reflex as the feet touch the perch. Another perching device is provided by the locking of the digits. The sheaths covering the tendons are ridged on the lower surface at the junction of the phalanges with tarsometatarsus. When a bird sits on a perch the weight of the body presses the ridged surfaces of the tendons and the ridges become interlocked.

Reference

1. Britannica Reference Encyclopaedia 

2. Knowledge Encyclopedia Animal!: The Animal Kingdom as you've Never Seen it Before

3. Images are taken from Zoo-Que and Google.

4. In Defense of Plants: An Exploration Into the Wonder of Plants

5. A Naturalist’s Guide to the Birds of India

6. Earth: A Sustainable Planet

Also See

• Migration & Navigation of Birds

• Archaeopteryx – The First Bird`s Fossil

• Parrots 

• Bats

• Bears

• Woodpecker 

• Birds

• Flightless Birds 

• Corals, Jellyfish and Sea Anemones

• Butterflies, Bees and Ants 

• Starfish and member of Echinoderm 

• Jawless Fish

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