Birdwatching or birding means going outside to enjoy watching birds. It is a popular hobby.  Someone who does this may be called a birdwatcher, but more often a twitcher  or birder.  They are usually amateurs.  The scientific study of birds is called ornithology.  People who study birds as a profession are called ornithologists.

Birdwatching is very popular in countries such as Britain and the United States.  It can be especially rewarding in spring when a lot of birds are singing and building nests to raise their young.  In spring and autumn many birds can be seen as they migrate.  In winter some other kinds of birds may be visiting from colder areas such as the Arctic where there is no food in the winter.

Equipment

It is useful to have a good pair of binoculars to help to see birds that are far away more clearly. Scopes or telescopes can also be used.  These can give greater magnification than binoculars (making the birds look bigger). They need to put on a tripod because it is difficult to hold them steady steady by hand. They are useful for looking at birds that stay in one place for some time such as ducks swimming on a lake, but no use for birds flying in the air or hopping quickly from one tree to another. 

Many birders like to take photographs of birds. This is difficult to do well unless one has good, expensive cameras and long lenses. Telescopes can be attached to cameras. This is called digiscoping. Modern phone cameras are very useful, and can produce good results. They are easier to use in many situations. But those who do use telescopes may need a "hide", usually a canvas tent. A hide means the birds cannot see you, and it keeps you warmer than being out in the open. Water birds are usually photographed from hides.

Also important is to have a good reference book with pictures of the  birds in your country. This is call a field guide. It tells you background information about the birds, which can be very useful. Apart from what they look like, the most basic information is what time of year they are in your area, and what kind of environment they prefer. Also they will tell you what the birds' songs and calls sound like. You will  discover that it often takes a long time to find a bird even when you know it is there from its song.

Songs and calls 
Songs are longer and more complex. They claim territory and are used in courtship and mating. Calls tend to be alarms or keeping members of a flock in contact. Most birds are songbirds. Those which are not give squawks or cries, which are like calls.

Bird watching 

Birdwatching (twitching) means spending one’s time trying to see as many different kinds of birds as possible. Twitchers keep lists of all the birds they have seen, and if they hear that a rare bird has been seen somewhere, they travel long distances to try to see it so that they can add it to their list.

Birdwatchers are useful 
Although birdwatchers are amateurs, they can be very useful, because they can tell organizations  about what they have seen. This is one kind of citizen science.  This information can be useful when discussions take place about possible damage to the environment, e.g. because of new developments (building).  It can help us to protect the birds, because we understand their needs.  Some birders help with bird ringing.  Putting a ring on a bird’s foot helps us to identify it when it is seen again so that we can understand where birds go and what they do.  Birders can also take part in bird counts.  In Britain a “Big Garden Birdwatch” project takes  place one weekend each year in late January.  Over 400,000 people watch the birds in their gardens for one hour and are asked to make a list of how many they see during this time.  By comparing the results with other years this helps us to see which birds are surviving well, and which ones are becoming less common.

Code of behaviour
Birders are always reminded how important it is not to disturb the birds.  This is particularly important in the nesting season.  If birds are nesting on the ground in fields or reedbeds one should never go anywhere near them.  Some birds get used to humans being near, but others are very shy of humans.

Organizations
Some national organizations which are concerned with birds include:
In the United Kingdom:
British Trust for Ornithology
Royal Society for the Protection of Birds
In the United States:
National Audubon Society
American Birding Association

References 

Birds
Hobbies