I agree you need to mow your lawn but the agreement to me is a matter of principle..
Your realtor should have made sure that all aspects of sale were done, that's why they make a commission.
I would first start with both realtors, for $300.00 they should split it.
1) Hire someone to mow it
2) File in small claims court
3) buyers lives out of state and even if you lose he has the expense of travelling..I would bet they would pay before incurring the expense of travel.
either way you win!
My mom had a peacock off Baldwin in Grand Blanc (it stayed with house when she moved), they are cool birds and worth the food to just have it around. they don't bother anything.