Being at the top of their niche of the food chain, raptors (especially the larger ones) have very few natural predators, but mankind has managed to provide several ways of decimating the raptor population. The following are some the major threats that are specific to raptors (the list could be much bigger if it included all environmental threats that have immediate impact or work their way through the food chain).
Egg Collecting :
There is still a significant problem due to illegal egg collection. It seems that in the egg collecting community, the rarer a species is, the more important it is to collect the eggs. Just so we have an historical record of what the egg looked like before the bird became extinct (or maybe it is just because they're worth more money).
Birds of prey have been treated as threats to valuable game birds, which are bred strictly for the right of rich people to kill. These people do not take kindly to having their game birds killed by wild animals for food, depriving them of the fun of killing them for sport. Some gamekeepers use various methods to remove the birds from their land, from destroying nests, shooting, trapping and poisoning. Despite now being illegal, there is much evidence that this still continues. During the two world wars, because of the decrease in game-hunting taking place, populations of birds of prey recovered significantly.
Habitat Destruction :
The habitats of much of wildlife are under threat due to the advance of mankind. As with pesticides, the effect is twofold upon the birds of prey, first by direct removal of the birds natural habitat & secondly, by removal of the habitat of their main prey. It is not only habitat destruction that affects the birds, but the increased use of the habitat by mankind, for example, the increase in take up of cabin cruise holidays in East Anglia is disturbing the nesting of Marsh Harriers.
Illegal Killing :
Birds of prey are often mistakenly seen as a threat to live stock (Red Kites eat a lot of carrion, often giving the impression that they killed the farmers lambs), because of this, farmers will often place poisoned food out to kill the birds or simply shoot them. Often birds of prey are seen as a challenge to hunters, who will set out to shoot them for fun.
While not directly affecting the birds themselves, in destroying a large part of the rabbit population, the disease had a severe effect on the populations of the birds dependent on rabbits as a food source.
Organochloride pesticides :
e.g. DDT. In general, these are not a direct threat to the birds, they come up through the food chain from their prey species. Being at the top of their niche in the food chain, birds of prey are very susceptible to attacks on the lower food chain. The pesticides have two main effects, directly they cause a reduced life expectancy of the birds. Secondly, and more importantly, they also cause thinness in shells of the eggs, resulting in breakages during incubation, as the eggs can't support the weight of the parent. Used widely in the 1950's & 60's - now illegal in this country.
This can be a direct & indirect threat to raptors. The pollution can be a direct threat by poisoning the birds or affecting the eggs (see pesticides) & the young or destroying the nesting sites. It can also be an indirect threat, by the ill effects on the prey species.
Road Traffic :
Aside from the general pollution caused by road traffic, cars themselves pose a threat to raptors. Several species have adapted hunting along the roadsides & central reservations of motorways, as these tend to be fairly safe havens for their prey, being largely undisturbed by man & large predators. The smaller birds (e.g. Kestrels & Barn Owls) are particularly prone to being sucked into the slipstream of passing traffic.