Perching mechanism of bird, different type of muscle, & Mechanism or perch

1. Shri Shankaracharya Mahavidyalaya, Junwani , Bhilai
Perching Mechanism of Bird
Dr. Sonia Bajaj
(Head of Department)

2. Perching Mechanism of Birds
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

3. 1. 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), while the
remaining two flexor muscles pass their
tendons to the hind toe or hallux.

4. The important flexor muscles
are following:
(i) Ambiens:
In some birds, an ambiens muscle arises
from the ilium and passes along the inner
surface of thigh. Its long tendon runs
beneath the patella bone round to the
outer side of the knee enclosed in a
special sheath and passes to the outer
side of the tibiotarsus to join the upper
end of the flexor muscle of the second
and third toes. This muscle has little role
in perching.
The function of the ambiens muscle in
perching is negligible and it can be
severed without affecting the perching
ability.
(ii) Peroneus Medius:
This muscle occurs singularly on the
anterior aspect of the shank, attached to
the upper part of the tibiotarsus bone. Its
tendon divides into three tendons, going
to the three front digits.

5. (iii) Gastrocnemius:
It is a calf muscle mainly concerned
with producing flexion of the toes in
the act of perching and occurs on the
back of tibiotarsus. Its tendon passes
behind the ankle and trifurcate to
supply the three anterior toes along
with peroneus medius muscles. These
tendons often act as a single unit.
(iv) Flexor Perforans:
This muscle is attached to the upper
part of the tibiotarsus (above the
knee). Its tendon going to the hallux
and is joined by a slip with the
peroneus medius. Thus, a pull up on
one tendon flexes all the toes.

6. 2. 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.

7. 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.
The Tendon Locking Mechanism functions not only in perching but also in other activities
such as swimming, clinging, prey-grasping, tree climbing, etc. Therefore, this
specialization of the tendon is found in a large amount of bird species though with
differences

8. The perching leg of a passerine (Chalk-browed Mockingbird) in three different
positions. With open toes fanning out (extensors working), with perched toes (flexors
working) and with a straightened leg and tendons at rest: toes droop together.

10. References-
Modern text book – R.L.Kotpal
Jantu Vigyan- S.M. sexsena
Jantu Vigyan- Dr.H.N. Baijal