The value of a knowledge of domestic birds is not limited to the use which may be made of it in keeping them for profit or for pleasure. Any occupation in which a great many people are interested affords opportunities to combine the knowledge relating to it with special knowledge or skill in other lines, to the advantage of those who are able to do so. Just as the large market or fancy poultry business may develop from a small flock kept to supply the owner's table or to give him a little recreation, many special occupations grow out of particular interests of aviculturists. Some of these have been mentioned incidentally in preceding chapters. In this chapter the principal occupations associated with aviculture will be discussed both in their relation to that subject and with respect to their possible interest for those who plan to devote themselves to lines of work which would qualify them for special service in aviculture.

Judging fancy poultry and pigeons. There is the same difference between selecting one's own birds according to quality and judging the birds of others in competition that there is between performing well in a friendly game and performing well in a competition where the stakes are important and feeling runs high. Many fanciers who are good breeders and also good judges under other conditions make poor judges in competitions. In judging at shows decisions must be made quickly, there is little opportunity to rectify mistakes, and if a judge makes serious blunders he is severely criticized. A person who deliberates a long time before coming to a decision, and who is very sensitive to criticisms of his errors, even though he knows that some errors are sure to be made by every one and that unprejudiced exhibitors make allowance for this, will not make a successful judge of poultry and pigeons. Judges as a class are not the men who know the most about standard-bred birds or who are the most skillful in breeding them, although some of the best breeders are among the best judges. Almost all fanciers get opportunities to act as judges. If their work is satisfactory, the demand for their services increases until in time their income from this source may be large enough to make it worth while to adjust their other affairs to their engagements at poultry shows.

Journalism. There were a few books on poultry and pigeons written in the first half of the last century, and a larger number immediately following the "hen-fever" period. These and the articles on poultry and pigeons in agricultural papers constituted the literature of the subject until about 1870. Then there appeared a number of poultry journals, most of which gave some attention to other domestic birds. The demand for special journals arose because many people who were interested in poultry were living in cities and were not interested in general agriculture; they wanted more information about poultry matters than the agricultural papers could give. Advertisers of poultry and pigeons, and of goods bought by aviculturists, also wished advertising mediums through which they could reach buyers at less cost than they could through the agricultural papers. The rates for advertising are based upon circulation, and if only a small class of the readers of a publication are buyers of a particular class of goods advertised in it, the cost of reaching them may be too great. Whenever any interest becomes of sufficient importance, journals especially devoted to it are issued, for the convenience of buyers and sellers as well as for the information they contain. Until about 1890 nearly all poultry journals were small publications which the owners looked after in their spare time. Then they began to increase in number and importance, and before long there were a great many that gave regular employment to editors, advertising solicitors, and subscription solicitors, who were employed for their knowledge of poultry and their acquaintance with poultrymen as well as for special qualifications for their respective departments.

Art. The illustrating of poultry journals and books, and of the catalogues of fanciers and other advertisers in poultry literature, gives employment to a constantly increasing number of artists. In order to successfully portray birds for critical fanciers, an artist must be something of a fancier. It is not enough that he should draw or paint them as he sees them; he must know how to pose birds of different kinds, types, and breeds so that his pictures will show the proper characteristic poses and show the most important characters to their best advantage. Since the half-tone process of making illustrations was perfected, the greatest demand is for photographic work, but unless an artist is able to work over and complete a defective photograph with brush or pencil, he cannot make this line of work profitable. Most birds are difficult subjects to photograph, and only a small proportion of the photographs that are taken can be used without retouching. A photographer may work for an hour to get a bird posed to suit him, and then, just as he presses the bulb, the bird, by a slight movement of the head or foot, may spoil one feature in a photograph that is otherwise all that could be desired. An artist who can draw birds can remedy such defects; the ordinary commercial artist cannot.

Invention. The most important invention used in aviculture is the artificial incubator. Methods of hatching eggs by artificial heat were developed independently by the Egyptians and by the Chinese thousands of years ago, and are still used in Egypt and China. The arrangements used in these old hatcheries are crude, and the success of the operation depends upon exceptional skill and judgment on the part of the operator. Operating incubators is a business continued in the same families for centuries. Each hatchery does the hatching for a community.

In the early part of the eighteenth century a French scientist named Réaumur, who was much interested in poultry, began to make experiments in artificial hatching and brooding. In 1750 he published a very full account of these and other experiments which he had made with poultry. His idea was to devise a modification of the Egyptian practice of hatching in ovens, suited to the conditions of a more advanced civilization. He succeeded in hatching eggs by utilizing the waste heat from a baker's oven, and also hatched eggs in hotbeds heated with decomposing manure. He applied the hotbed principle to the brooding of chickens with some success. But the methods that he devised were not adapted to general use.

After Réaumur many others experimented with artificial hatching. Some of the ideas were obviously more impractical than those of Réaumur, but the experimenters tried them out and sometimes succeeded in hatching chickens by very peculiar and laborious processes. One man in England, in the latter part of the eighteenth century, hatched some chickens from eggs placed in cotton batting in a sieve adjusted over a charcoal fire in a small fireplace. The fire was watched constantly for three weeks, either by himself or by some member of his family. He demonstrated that eggs could be hatched in this way, but not that it could be done profitably. Practical incubators were not produced until about forty years ago.

Although incubators and brooders have been brought to a relatively high state of efficiency, they are far from perfect. Inventors of the best machines are still studying ways to improve them. In this and many other fields there are opportunities for inventive genius.

Education and investigation. Lectures on poultry have been given occasionally at agricultural institutes in the United States since about 1860. After 1890 the demand for such lectures, and the number given, constantly increased, and ability to speak in public became valuable to one versed in aviculture. Then the study of poultry culture was introduced into agricultural colleges, and a new field was opened to poultry keepers with a faculty for teaching, and for trained teachers with special knowledge of domestic birds. The teaching of poultry culture impressed upon those engaged in it the need of scientific investigation of many problems not clearly understood even by the best-informed poultrymen.