One of the challenges of establishing a new lawn is to keep the grass seed right where you planted it. Birds find the seeds appealing, and rain and watering can wash it away, creating thick lush spots in some areas and bare patches in others. Covering the seed at planting time keeps it in place, helps the soil retain moisture until the seeds sprout, and prevents the sun burning the tender grass plants.
Work with the natural components of the soil and the grass by mulching a new lawn with about 1/4 inch of straw, peat moss, dried grass or sawdust. As the grass seed germinates, the mulch discourages birds from eating it, and continues to decompose, enriching the soil with nutrients. The mulch also helps the soil retain moisture, improves air circulation and keeps the seed in place, particularly on uneven ground. Don't use hay or grass clippings, as both may contain weed seeds.
A single layer of burlap provides the same functions as straw or peat moss by allowing the rain and air through the openings in its fibers and keeping the seed in place. The drawback of this traditional method is that you may uproot new grass i you pull it up. Instead, leave it in place and allow it to decompose in the soil.