how can you tell if an egg is fertile?

[eggs]

i seen my roo with her about a week or two ago and i cant tell if the eggs are fertile

 

[speckledhen]

Crack it open or incubate, that's the only way. Check out the photos in this thread:
https://www.backyardchickens.com/forum/viewtopic.php?id=16008

 

[eggs]

thanx her eggs are fertile