There are a lot of bird trapping techniques practiced all over the globe. Catching these birds are mainly motivated by hunting them for the food.
There is a difference between hunting and bird netting. Hunting do not require the bird to be caught alive while trapping a bird do not harm the bird in anyway and the bird is caught alive. These alive birds are then used in many research programs such as ornithology research.
Some of the wild birds are also trapped for keeping them as a pet at home and also for the display at zoological gardens. Every country has specific laws for bird trapping. These laws are to protect these species. Bird trapping is not illegal in most of the countries but it is controlled to certain extent.
In bird netting, we can save the bird from harm. Hunting kills, the bird, which decreases the population of the birds. Trapping can also increase the population by keeping them in protection for reproduction.
Many of the wild animals are very expensive. People pay a lot of money to keep them as pets. Trapping those birds can make a lot of money.