It goes without saying that lighting is fundamental to any photograph, and for bird portraits there are a few things to consider since it is natural light that you have got to play with.
Feather detail is an important aspect of a good bird portrait. You want to be able to clearly see the colours and detail in the bird’s plumage, and of course the lighting conditions play a part in this. If, for example, you photograph a black-and-white warbler on a bright sunny day, with the sun high in the sky, it will be difficult to render good detail in both the black and white plumage because of the very high dynamic range. As a result, you’ll be lacking detail in some areas.
Shoot on an overcast day, or when the light is softer, and the dynamic range is reduced by several stops. This means that the entire range of tones can be recorded.
Make sure that you know your camera and try to photograph in lighting conditions that will allow you to capture a full range of tones. You can easily check this on the histogram.
Bright overhead sunlight also creates shadows, this ruins a bird portraits. Aim for your shoot to be at either end of the day when the sun is low, meaning there are less shadows and warmer tones. Not to mention, these are normally the times that birds are more active also, so you will get a lot more portrait subjects available for your photoshoot.
The direction of sunlight is also a factor and generally it is preferable to shoot either with front lighting or backlighting. Side-lighting tends to be less effective for bird portraits, often throwing a shadow across part of the bird’s head. Front lighting is best for bringing out the colours in a bird’s plumage and will produce a more evenly lit portrait. It also makes it easier to expose correctly as the contrast is lower.
Backlighting can also be very effective for bird portraits, especially those with a clearly defined and recognisable shape or plumage that picks up sunlight to create an attractive rim lit effect.