The trust is a charity dedicated to scientific research, and its report contains fascinating information about the birds' history, biology and habits. Pheasants originated in the Far East, and were probably imported into Britain by the Romans; the Latin name Phasianus colchicus reflects the legend of Jason and his Argonauts, who returned from seeking the golden fleece in Colchis (now part of Georgia), bringing pheasants with them.
Today, the pheasant is easily the most numerous game bird in the British Isles. Yet even when it is not shot, its life expectancy is pitifully short: most live just one year, and only outstanding survivors reach three or four.
They have many natural enemies. Crows, magpies, rooks, jays and rats eat their eggs, and stoats massacre whole broods of chicks. At this time of year, when the hens are nesting on the ground, they are vulnerable to foxes. The report does not mention a theory I have often heard gamekeepers expound: that an incubating bird's metabolism slows down, so that its scent is greatly reduced, thus giving it a measure of protection.
The potentially explosive part of the report is the section on shooting, which reveals what a major industry the artificial production of pheasants has become. More than 20 million birds are hand-reared in Britain every year, and about 12 million are shot; the sport is now so popular that the overall annual bag is five or six times higher than in its heyday, 1900 to 1910.
Those in favour point out - as the report does - that management of land for shooting does much to enhance the landscape: woods are thinned to encourage the growth of shrubs; coppices are planted; hedgerows are maintained. A survey of 712 landowners shows that among estates where pheasants are reared, 61 per cent had planted new woods, compared with only 21 per cent of non-shooting properties. In short, estate owners spend huge amounts on improving the environment for shooting.
Research has also shown that establishing a shrub understorey is beneficial to many other birds, among them willow warblers, spotted flycatchers, chiffchaffs, song thrushes, blackcaps, garden warblers and nightingales.
Similarly, benign agricultural practices, such as leaving unsprayed conservation strips or headlands, helps species such as buntings and finches.
So far, so good. But many landowners now fear that the Government, after it has got rid of fox-hunting, will seek to ban the rearing of game birds - something that has already been done in the Netherlands.
There is no doubt that a ban here would have far-reaching ecological consequences. Many shoots would close down. On those that went under, woodland maintenance would cease and, with fewer gamekeepers, predators would flourish to the detriment - or even disappearance - of game birds and songbirds.
No true countryman wants this to happen. Yet a feeling is abroad that some shoots are too commercial, and that bags are obscenely large. A few far-sighted estates, notably Raby Castle in Co Durham, have given up rearing, and returned to the healthier practice of nurturing wild birds only.
Raby has shown that substantial stocks of game birds can be built up by a combination of strict predator control in spring, and sympathetic husbandry throughout the year. My bet is that, with the threat of bans in the air, more landowners will soon be following its example.
`The Pheasant' is available from the Game Conservancy Trust at Fordingbridge, Hampshire SP6 1EF, price pounds 10.