One frequently overlooked lawn weed contributor is birds. Different backyard bird species enjoy weed seeds as part of the daily diet. The moist journey through the digestive system can give seeds a boost.
Unfortunately (for your lawn), weed seeds survive in birds’ digestive systems. When birds poop, the seeds are deposited, ready to sprout when conditions are optimal.
If you look on the ground directly under common perch sites, including mailboxes, branches, fence posts, and bird feeders, you’ll frequently find weeds sprouting. Also if you look along the ground below their favorite tree branch and along the flight path to the bird feeder, you’ll often see a trail of growing weeds here as well.