what does caliber mean
this talks generally about hunting stuff, i need to know if for example birdshots can do the job or not
Caliber is the dimension of a specific bullet. It can be just the diameter or it can also contain the length of the shell. Basically, the bigger the caliber, the bigger the bullet (*expect with shotguns when using gauge as a measurement of caliber, the bigger the gauge the smaller the diameter of the barrel).
In hunting, there are specific minium caliber requirements, depending on the hunted animal and your local regulations.
Birdshot could do the job, but it's risky. I wouldn't recommend it. There are three main shotgun ammo types: Birdshot (tiny balls use for hunting birds), buckshot (bigger balls, used for hunting deer) and slugs (a solid ball of lead).
I'd recommend you don't use birdshot, because its has the small balls for a reason, so it doesn't damage the birds too much (doesn't tear up all the meat) and for a higher hit chance at range, but you get less damage. It can still be deadly at point blank range.
Shotguns are powerful, but like with other firearms you and still survive being shot. Think this through before doing anything that you might regret.
If you want a good explanation of shotguns, here's a video on the basics
