Serious bird watching requires good optics and many birders are prepared to spend thousands on their binoculars. If you think about your needs, you'll likely find yourself making a little list which might include:
Fortunately there are many binoculars available in quite compact roof prism designs which are phase coated for excellent color throughput and rugged enough to survive a fall or a soaking. At the risk of making a broad sweeping statement, birdwatchers generally favor binoculars with 8 to 10 times magnification with an aperture of 40mm (sometimes a little more) in a roof prism design. Any more magnification and you'll start to want a tripod to cut down on the handshake effect.
Phase coatings are a good idea as they ensure all colors are focused to the same focal point thus avoiding any unnatural color tinge to your viewing. Those terms are explained in a bit more detail on the Understanding Binoculars page if you want to check them out more.
Remember if you wear glasses while birding and using binoculars you'll need to pick a model with eye relief (the distance from the eyepiece lens to your eye) of 15mm or more to allow for the extra distance caused by having your glasses in the way.
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