Recently I went for a short trip to a local park, Rosser Park, Gold Coast, Australia, near to where I live and was fortunate to find a couple of beautiful birds. At this park there is a large lake to attract the water birds and also many native grevilleas and flowering shrubs to attract the native birds and honey-eaters.
Birds are beautiful creatures to photograph, sometimes they are difficult and sometimes easy to find. Generally where the birds are feeding on flower nectar they will come and go very frequently and it is just a matter of waiting until they come near you. In the case of the above Rainbow Lorikeet I used a 300mm f/4.0 lens and a monopod to steady the camera and lens. The birds were frequently moving around from flower to flower and were generally relatively easy to follow.
Sometimes a 300mm lens is not quite long enough for birds, particularly smaller ones. An economical way to get longer is to use a 1.4 times or 2.0 times teleconverter, but using the teleconverter will cause loss of light and this leads to a 300mm f/2.8 lens being better than the 300mm f/4 lens that I used here. The cost of f/2.8 lenses will be significantly more than f/4 lens and this can amount to many thousand dollars.
The image of the White-faced Heron was quite easy to capture as the bird remained motionless for a considerable time, again this bird was captured with the 300mm f/4 lens. A 300mm lens is plenty for a bird such as this as they are quite large. With the above bird I had to back off a little to fit it into the frame.
For smaller birds telephoto lenses can sometimes never be long enough, but for birds such as the heron above, sometimes even a 200mm lens can be enough.
Selecting a lens is quite complicated as the are some important considerations.
The possibilities for selecting lenses for this type of bird photography are summarised here for the Nikon system.