Though it is the smallest of all seeds, yet when it grows, it is the largest of garden plants and becomes a tree, so that the birds come and perch in its branches (Mt. 13.32 NIV).

The same birds that Greg Morse speaks about in Mt. 13.4 who pluck the sown word along the path are the same ones who perch in the mustard tree which Jesus says represents His church (vs. 32). There are evil people masquerading as Christians and church leaders.

Also, two other ways Satan influences us are 1. people of the world, and 2. from our fallen flesh.

The unredeemed are the devil’s own: The one who does what is sinful is of the devil, because the devil has been sinning from the beginning (1Jn. 3.8a NIV). These are unable to see the truth of God’s Messiah: The god of this age has blinded the minds of unbelievers (2Cor. 4.4a NIV). Satan is actively working in lost people as he did in us before we turned to Jesus: …in which you used to live when you followed the ways of this world and of the ruler of the kingdom of the air, the spirit who is now at work in those who are disobedient (Eph. 2.2 NIV).

Therefore, it can be said, the Christian battles the The World, The Flesh, and The Devil.

Beware of the Birds: How Satan Sabotages Sermons — Desiring God