On some levels you will need to collect chickens.
To collect chickens you have to first match up 3 eggs, which make a cracked egg.
The cracked egg will be in the place that you moved the third egg TO...See below.
Then you need to match up 3 cracked eggs to make a chicken..
The chicken will then fly across and be added to your score...
Here is a video showing how it all works.
This is level 38..