Something you hear all the time is, you must need a large Telephoto lens to get those photos, Well yes, but with the right amount of patience a little ingenuity
Those close up intimate shots are still achievable with the smaller lenses. The use of home made hides is one option, allowing your subject to approach you with out disturbance. Your personnel level of field craft can be improved beyond what you think you can achieve. And of course use the hides at local reserves or feeding stations to get that closer than normal shot.
Always place the subjects welfare first, at the first sign of distress back of and allow it to calm down and perhaps get a bit more used to you. Wait for some preoccupation i.e. feeding, Bathing, breeding, but be aware these periods may present behaviour out of the norm.
REMEMBER many of our birds, wildlife and plants are protected by UK and International laws, and must not be disturbed, or photographed at certain times without licence.
The performance of Zoom lenses have come a long way from those early days, so if you have one use it to it’s fullest. Now many have a little softness at the full extension so back of a bit, if you can. The internal HSMotor has been a boon and coupled with VR is now bringing some really tack sharp images to the fore. And consider the benefits of weight, size and performance of lugging a large lens around the place, I would certainly recommend a 70-300 VR ED HSM lens and at less than £450 it is a no brainer. Really good for birds in flight.
With all the permutations available to the modern DSLR owner, all achieving a well exposed photo it becomes a matter of what it is you really want to communicate to the viewer. But one thing is try to get the shutter speed to equal at least the focal length of the lens in use, I.e. 500 mm lens try to keep the speed up to 500 by adjusting the aperture and ISO settings, remembering of course the lower the aperture number the less of the background will be in focus.