Field of vision
Depending on the habitats they live in, but mostly on their place in the food chain, birds have adapted their fields of vision to suit their specific needs.
We humans have developed forward, stereoscopic vision. Our field of view is about 180 degrees wide (most of which stereoscopic) and about 120 degrees high. This provides us with a clear view of what is ahead of us, but leaves us with a large blind spot at the back that we cannot see at all. Such eyesight is typical of hunters. Similarly, other predators, such as e.g. birds of prey, also have good forward vision. An example of this, a Pallid Scops Owl, is shown below.
Example of forward stereoscopic vision: the Pallid Scops Owl
Diurnal raptors also have forward vision, as the example below, a Kestrel, shows.
NB: Note that raptors have semi-transparent inner eyelids that they close, especially in fast dives, to protect their eyes in-flight.
Other birds, although not predators, can have forward vision if they are not preyed upon, for example various corvids. For lack of suitable photos from Oman, we show here an example of such a bird from Australia, the Australian Raven. It is obviously not worried about being preyed upon; not even its wing feathers are designed to allow silent flight. Its forward vision, although not as extreme as an owl's or a raptor's, allows it to find food, often carrion, at long distances.
Example of forward vision in a non-raptor: Australian Raven
On the contrary, birds that are preyed upon - especially, for example, ground-feeding seed-eaters, tend to have wide-angle vision, allowing them to see predators trying to surprise them from behind. On the one hand, this reduces the size of their blind spot at the back, but it also has the disadvantage of reducing the forward field of vision with stereoscopic sight. That is the reason why many birds with wide-angle vision will look at you (or objects) sideways. One example of such a bird with wide-angle vision is the Laughing Dove. The photo below shows how far apart, on the side of the head, its eyes are located.
The wide-angle vision of a Laughing Dove, with eyes on the sides of its head
Another example is the Rufous Bush Robin (see below).
Rufous Bush Robin glancing at an object on the ground sideways; at the same time it may be monitoring the sky above
Particularly vulnerable birds, such as e.g. some species of snipes, have gone even further in developing eyesight that gives them an all-round view.