The Richest Bird Habitat in the world
There is no doubt that the tropical forests hold a greater number of birds of a wider variety than any other habitat. Although they occupy only 6—7% of the land surface of the globe, they hold 40% of all known animals and plants and many of the world’s species occur exclusively there.
For example, the lowland forests of eastern Brazil hold 940 species: 214 are endemic and of these 80% are of humid lowland forests. But sadly these forests are among the most endangered habitats in the world as struggling ’emergent’ nations seek to exploit their timber and minerals.
This habitat is full of secretive species and there seems little doubt that some of the endemics there have become extinct without their ever having come to the notice of science.
Other great centres of endemism (having range restricted to specified areas) survive in remote or protected areas of East Africa, particularly in some of the isolated mountain ranges. Among the most productive are the Usambaru, Uzungwa and Uluguru Mountains in Tanzania and some of the coastal forests such as Arabuko-Sokoke in Kenya.
The richest bird habitats in Britain
Britain has a great variety of habitats and figures derived by Fisher and Flegg from the Common Birds Census suggest that scrub is generally the richest habitat with 17 birds per hectare (2.5 acres). Scrub is rich in birdlife because as an intermediate stage between heath or marsh and mature woodland it attracts birds from several habitats.
True scrub includes species of shrub that will never grow tall enough to create woodland and many birdwatchers prefer to wander among the vegetation of varying height, such as gorse, hawthorn, and elder because the birds are generally easier to see than those in mature forest.
Scrubland is closely followed by deciduous woodland and suburban areas. Deciduous woodland is the natural habitat of much of Britain and holds both a large number of birds and a great variety of species, though the mix varies considerably according to how dense the wood is and the variety of trees present.
The most productive woods are those ‘untidy’ ones with clearings and scrubby areas and fallen as well as standing timber. At the other extreme is farmland with six birds per hectare; water areas with 2.5 birds per hectare and bare uplands and hill grasslands with just one bird per hectare.
In winter the pattern of British birdlife changes significantly with both international migration and local movements. The British Trust for Ornithology’s Atlas of Winter Birds Survey 1981—4 has highlighted some of the best places to watch birds. The 10 km (6.2 miles) square with the highest number of species was that in east Kent including Stodmarsh and the North Kent Marshes where 166 species were located.
Another in north-west Norfolk, including the RSPB reserve at Titchwell, returned 164 species. All the areas with the highest number of species were along the coast in the south-east quarter of England. The highest inland total was 148 from a square in Leicestershire including part of Rutland Water.
At the other extreme, the mountains of central Scotland were found to be nearly devoid of birds in winter, and even relatively small upland areas such as Exmoor and Dartmoor returned both few species and small numbers of birds.
Britain is particularly fortunate in having a wealth of coastal mudflats and saltmarshes which are unbelievably rich in animal life, providing a tremendous store of food for great concentrations of wildfowl and waders. Extensive counting and ringing programmes have shown that the British coastline holds about 1.5 million waders in winter — about 40% of the European total.
Over a half of the waders winter at just 10 top sites: Morecambe Bay, the Wash, Dee, Solway, Severn, Thames, Humber, Strangford Lough, Firth of Forth and the Chichester/Langstone Harbours complex. While the waders are attracted by marine worms, molluscs, etc, many of the large numbers of ducks and geese are drawn to the salt-tolerant plants.
For example, brent geese and wigeon are particularly abundant where eelgrass is present, though in recent years this important food has been affected by pollution. Where these salt-tolerant colonize the mudflats plants naturally, the marsh created soon rises by deposition of silt trapped by the stems and these ‘saltings’ then become important high-tide roosts for waders.