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If you want to help find out the facts about bird populations, and help conservation efforts in the process, can join in a bird census. This might be a local count of selected species or a national scheme.

There are three types of bird census: partial, full, and breeding. Many large organizations run annual bird censuses and these help with understanding conservation, breeding patterns, and population numbers.

Censusing birds may sound like a grueling task involving difficult days spent counting birds in all weather, but I have spent some of my favorite days in the field doing just this. It’s not just me, as large number of birdwatchers take part in censuses. Even during winter every month through the winter, lots of bird lovers count wildfowl, while many more turn out on estuaries to count waders.

Do you know what vagrant birds are?  Find out here

Photo of flock of birds

How To Count Large Flocks

You may think that counting a large flock of birds would be impossible but this is not so. A large, very conspicuous bird such as the mute swan, which rarely occurs in flocks of more than 100-200, can be counted individually with great accuracy.

Geese can form much larger flocks and these cannot be counted with the accuracy possible with swans. Going through a flock of several thousand geese in a field, one by one would be a long and arduous task.

One of my favorite techniques is to count in a larger unit, such as fives or tens but sometimes even 50s. With a bit of practice, you can become experienced in the visual technique of putting the birds into such groups as he scans the flock.

A flock of geese taking off may be out of sight in less than a minute. Although part of the skill of wildfowl counting lies in taking care not to flush the birds, field workers have developed a quick visual technique for estimating the size of a flock if the birds do get frightened.

It is a good idea to run your eye briefly over the whole flock as it flies, gaining an overall impression. Starting from one end of the flock, you can count hundreds of birds at great speed, perhaps in batches of 10s or 20s. Once you know how much space 10 or 20 take up, it is much easier to count the flock.

Next, you need to count how many areas of similar size and density the flock contains. A hand tally counter is great for recording numbers without losing track. With some large flocks, losing count is easily done.

Once you get used to counting large flocks, you will notice that you improve your ability to estimate flock sizes in all circumstances, including poor visibility.

Do you know how birds fly?  Find out here

How To Count Hidden Birds

It may seem odd that you can count birds that you can’t see, but it is possible. It is conceivable to rely on your ability to hear and identify bird songs than always see and count the birds.

If you move quietly through the area, you can listen to singing males of the different species and plot the position of each.

Great For Conservation

Counting birds provide the knowledge for a whole range of decisions about conservation. Those working to conserve threatened bird species need to know which are increasing and which are declining.

A census can yield useful clues as to precisely what is affecting the numbers and in which areas. The factors could include changes in the food supply, icy weather, drought, or a natural population cycle.

Certain birds can be used as environmental indicator species. Some birds are counted to monitor the effects of acid rain and climate change. One study was completed on dippers.

If the dippers are shown to be taking up larger territories than usual, this indicates a decline in aquatic insect larvae that they feed on.

Complete Census

A complete census aims to count every bird in a population throughout its range. Such a census is usually carried out on a relatively large or conspicuous bird such as the mute swan, the gannet, or the great crested grebe.

Very rare birds, too, can be counted completely and regularly. Many organizations try to monitor our rarest breeding species every year. With some of these species only having at most a few tens of pairs, all found in only a handful of localities, counting the birds is fairly easy.

Some larger populations can also be censused completely because of their restricted range. In Britain, two species of geese, the pink-foot and the greylag come to Britain for the winter from breeding grounds in Iceland.

In the first few weeks after their arrival in autumn, they are concentrated in large flocks in a small number of locations, mainly in eastern and southern Scotland and northern England.

For many years, a census has been attempted every early November, involving about 150 birdwatchers. During a single weekend, these volunteers visit the areas allocated to them to count the geese, and although both populations number in the region of 100,000 birds, the counts are complete and accurate.

Photo of flock of birds

Partial Census

For the great majority of birds, however, it is impossible to think about a complete census. I would not know where to begin counting blackbirds or blue tits, and the same is true for many larger birds, including ducks and waders.

For these species, it is necessary to take a small population sample from each species. While it may not be possible to learn directly from this method what the total population is, any changes taking place over several years can be detected.

Audubon runs their Christmas Bird Count annually between Decemer 14th and January 5th and is great fun for all the family.

Breeding Census

The third type of census is more concerned with distribution than with numbers. The British Trust for Ornithology monitors the population of 118 breeding bird species across the UK, with the help of almost 3,000 volunteers.

Observers are given a 1km square area of land and to count all the birds they see or hear within and record any nests for colonial nesting birds.

In the USA, the North American breeding bird survey has been the cornerstone for conservation and management for over 50 years.