Why spotting scope can be used for watching the moon, astronomical telescope can not be used for bird watching

I wonder if you have such a question, why spotting scope can be used for watching the moon, astronomical telescope can not be used for bird watching? And the magnification of astronomical telescope is higher than the birdwatching scope, so directly use astronomical telescope instead of spot scope in the end reliable or not?

I can tell you that it is not reliable.
First of all, to clarify the environment of bird watching.
1, working conditions (relative to astronomical telescopes) poor, long-term face a variety of mud, dust, water, etc.
2, need to long-term flat or upward looking
3, with the movement of the bird often focus

So the characteristics of the spotting scopes are:
1、Birdwatching scopes are sealed dustproof and waterproof

2, the eyepiece has its own 45 degree elevation angle, and positive
3, there is a focus ring or focus hand wheel, one-handed focus, and the focus stroke is short
The above three points in the astronomical telescope can not do:

1, completely unsealed not waterproof
2, fully reversed phase, and difficult to look up.
3, focusing with the focus barrel, is the front and back of the telescope. Focusing stroke is long (because the astronomical telescope needs fine focusing). And then installed so heavy a prism and will change the center of gravity, the tripod is easy to fall down.

There are some other aspects, such as astronomical telescopes are heavier than spotting scopes, and the lens coating is very unscratch resistant. There is also a very important point is that: in addition, because birds often move,it needs fast focus and zoom capabilities, spotting scopes can continuously zoom, astronomical telescopes can only keep changing the eyepiece.
In short, what mirrors do what things.