Why leeches are important?

Leeches are important to human being for so many reasons, which are as follows:

As food: Certain fishes, ducks, and other birds, turtles etc. eat leeches. Leeches are also used as bait to catch fish. Thus leeches form food of many animals which arc used as food by man.

 As pests : Man faces both direct and indirect problems because of leeches.

(a) The leeches parasitic on fishes cause serious losses to fishery.

(b) Cattles, especially buffaloes, which pass considerable time in ponds, suffer due to leeches. The wounds caused by leeches become infected with bacteria and this causes crippling effect and death of cattle.

(c) Cattles and horses are often blinded by their attacks.

(d) The bite of Indian land leeches (very common in forests) is very painful. Due to their attacks horses are driven wild and men suffer serious loss of blood. The soldiers of Napoleon were put to serious trouble by leeches.

Medical importance: Leeches suck the blood of their hosts without causing pain. Due to this reason leeches were used extensively in the past for blood letting. It was believed in the past that removal of bad blood cures many diseases. Tribals still use leeches for this purpose. Hirudin as an anticoagulant remained in use in hospitals for a long time. However, it is not used now.

Why birds are beneficial to man

  1. Biological control: Birds are of great use for man and his crops, as they control insect pests and other vermins. A large number of insect pests like potato bugs, Colorado beetles, chinch bugs, locusts, caterpillars etc., are favorite food of the birds, like white stork, rosy pastor, starlings, tits etc. Owls, kestrels and hawks are other birds which feed on rats, mice etc., which cause severe damage to crops and godowns of cereals and spread fatal epidemic diseases. Thus the birds are most effective natural checks on the pests and vermins.
  2.  Scavengers: Several birds like vultures, kites, crows, hawks and eagles etc., feed on dead remains of cattles and other refuses left decaying in the villages. Thus many infections which can spread due to the decaying bodies are controlled by these birds.
  3.  Flower pollinators. Large number of birds of diver families possesses special adaptations to extract nectar from flowers, which is rich in carbohydrates and is good nourishment. Such birds are of great value since they pollinate the flowers.
  4. Seed dispersal: Birds eat fruits and berries. Their seeds come out along with the waste matter after passing through the digestive tract. It is confirmed that the seeds, after passing through the alimentary canal of birds, produce very strong seedlings in comparison to seedlings produced in richly manured fields. Also, the seeds are dispersed for long distances by the birds.
  5. Food for man: Both flesh and eggs of several birds are eater, by men. The food value of egg and flesh has been recognized by men. Eggs of fowl are compared with milk due to its high nutrient value. Eggs are also used in preparing biscuits and pastries etc.
  6. Bird nests: In Burma and China nests of swifts are regarded as good food. This nest is composed of saliva of the bird.
  7. Fertilizer: Guano is the excreta of birds. It is of great commercial value because it is a good fertilizer for land. It consists of Nitrogen, Phosphates, Calcium and Iron etc., which are essentials of good manure. Guano is found in enormous quantities on coastal areas of Peru, where there is little rainfall. Millions of migratory birds breed here. Large quantities of guano are exported to other countries from Peru. There is possibility of getting liquid guano from the colonial nests of water birds in India.
  8. Feathers: Colourful and soft feather covering of many birds have been utilized since ancient times.
  9. Feathers of a large number of birds arc being used in making pillows, blankets, clothings,
    sleeping bags, fans and toys. Badminton shuttles arc manufactured by feathers. These are also used by natives in the tail of their arrows. Large number of birds like ostrich, duck, geese, golden eagle, rhea, peacock, valley quails, crested cranes etc. is valued for their feathers.
  10. Medicinal use: Flesh, feather and eggs of a few birds are used in preparing medicines. Flesh of pigeon is valued for the cure of paralysis. These are mainly used in Ayurvedic and Unani medicines.
    Egg of fowl is used in preparing tonics and in growing cultures of viruses, bacterias, nematodes etc.
  11. As a Friend of man: Birds like peacock and eagles destroy enemies of man like poisonous snakes, scorpions etc. Some birds help man in hunting. For example, some sparrows cry on seeing carnivorous animals like lions, tigers etc. Path sparrow follows king cobra and cries like a danger signal.
  12. For amusement: Sweet singing birds are one of the best attractions for poets and naturalists. Wild fowls, ducks, quails, herons etc. are famous game birds all over the world. Parrots, mains and other birds are kept in cages in houses for their plumage and ability of producing human voice.
    Pigeon and cocks arc trained for plays and fights. Cock fighting is relished by the people very much.  Pigeons have been used for carrying messages during wars and love affairs since ancient times. Several birds are being used now a day for performing scientific experiments.

Function of Pectin in birds

Pectin is the most puzzling organ of the eye of a few reptiles and all birds (except kiwi). It is a highly vascular, pigmented, folded, and comb-like structure. It projects into the vitreous humour from the retinal surface ventral to the blind spot. It is soft and almost rectangular.

 Functions of Pectin

Several functions have been assigned to the Pectin:

1. Probably its main function is to bring oxygen and nourishment to the retina, which is vascular in birds. It allows exchange of materials between the blood stream and the vitreous humour.

2. It is possible that the irregular shadow cast by this organ on the retina helps in detection of movements of an object. The function is supported by the observation that it is larger and much folded in predatory birds, and is small and smooth in nocturnal birds.

3. It may in some way be connected with accommodation. It probably regulates liquid pressure inside the eye which is changed by the change in the position of lens during accommodation. Last two functions arc yet to be confirmed.