A fielding team has 9 fielders, if we exclude the bowler and the wicketkeeper. But sometimes, there come some free souls in the form of dog and bird who have no clue what’s these guys are doing with a bat and ball.
Now what happens, if some player hit a shot and it struck a dog or a bird on the ground.
The ICC rule is if a batsman hits a shot, and the ball gets stopped by a dog or a bird that happens to enter the ground at just the right time, it is not considered a boundary (even though the ball may well have been crossing the boundary line before it got stopped).
However, for fixed obstacles such as a tree, there is mutual agreement among captains and the umpire to consider it as a boundary if the ball hits the tree . Even if the ball hits the tree directly, it is not considered six, but a boundary only.
Next you may be wondering which cricket stadium will have a tree inside ?
A cricket stadium in Pietermaritzburg, South Africa has a tree inside the ground.