Bird watching and Nature
A wide field of view and a clear bright image are important, 8x magnification is ideal, this gives a clear, stable image, but is powerful enough to see detail. (Consider models with magnification in the range of 7x to 10x).
Large objective lenses are best as they will let in more light and work better in low light, but too big and they will be heavy to carry around. We would normally suggest a binocular with objective lenses around 40mm - 45mm, these should be comfortable to carry, yet performance in low light is good. This type will work very well even after sunset, for twilight observation select 8x56.
For a very lightweight binocular 8x21, 8x25 or 8x30 will perform well in daylight conditions
We don't usually recommend the ruby anti UV coating for birdwatching and nature viewing. Although anti-UV coating can improve image sharpness in bright conditions, the coating can make the image slightly blue.
For longer range birdwatching we would suggest a telescope with magnification of about 25x mounted on a good solid tripod, many scopes are available with zoom magnification. Waterproof models can be useful, as well as water protection a fully waterproof model will not fog in damp early morning conditions.