If another creature you control has -1/-1 counters on it when it dies, Buzzard-Wasp Colony's ability will include those as well. This may result in Buzzard-Wasp Colony dying.

You may end up putting the appropriate counters on more than one permanent. For example, if you control two Buzzard-Wasp Colonies when a creature dies, you'll put the appropriate number of each kind of counter onto both of them.

If enough -1/-1 counters are put on a creature you control at the same time to make its toughness 0 or less, Buzzard-Wasp Colony's last ability will see all of the +1/+1 counters it had when it died as well as the -1/-1 counters it had, and an equal number of each of those types of counters (plus any other applicable counters) will be put onto Buzzard-Wasp Colony.

Buzzard-Wasp Colony's last ability doesn't cause you to move counters from the creature that died onto it. Rather, you put the same number of each kind of counter the creature had when it died onto Buzzard-Wasp Colony.

Buzzard-Wasp Colony's last ability puts all counters that were on the creature that died onto Buzzard-Wasp Colony, not just its +1/+1 counters.