Similar to the usual portrait photography you can also portray birds. However, it is much more difficult to get close to the bird in order to get a full format picture of it, let alone to take a picture of only its head. If you succeed in this, you can create very interesting images. But to get so close to a bird, you need the right individual, a lot of patience and luck. In rare cases you don't even need a lens with a long focal length.