Based on 2 Corinthians 4:4

 2 Corinthians 4:4 
New International Version
The god of this age has blinded the minds of unbelievers, so that they cannot see the truth.

The owl, which sees very well in , darkness but also considered an "unclean" animal sees the cross which is representative of Christ. The owl being  the symbol of a sinner "unclean" coming to Christ and thus being able to see in the dark.