how to make an animal trap to get food when you're in the jungle?

say if you have a square box and a triangle box, can the animal easily come out of the square box or the triangle box?

I need to know before 3/27/08. For example: my dad builds triangle wood traps to catch pigeon (to study the and not to eat them) so Iwant to know how does the triangle shape help to catch the pigeon. to study them not to eat them!!!!!

I won't harm them i just wanna learn about them and will let them go after i have caught them, please, c'mon.