Hearts from animals being bred are rendered behind water and ice blocks when floating.

Hearts should float in front of background.

When breeding chickens, sheep, cows, and pigs by a river or frozen lake, hearts will be rendered behind the translucent blocks. Parts of hearts in front of dirt, animals, or leaves are rendered normally.

I was not able to reproduce this by breeding dogs in front of glass blocks. I've only seen this around ice and water.

I breed chickens and cows regularly for XP and drops, but only saw this on 13w09c.

Steps to Reproduce:
1. gather animals by ice or water. Go to a higher land position.
2. Feed animals.
3. Watch hearts.