I'm another that uses pieces of pegged down pea netting across prepared soil, just as TJ suggests.
I also do the same with pots of bulbs in the Autumn, thus foiling the blackbirds, who root about in the compost thus displacing small bulbs & squirrels who dig about in any uncovered pot!
My tip- when pricking out seedlings into bigger modules/pots, add a small cut off piece of coloured drinking straw as a 'label' for each seedling. Then add the same colour straw to a pot that actually has a label. That way you only use one label, but you can tell which tray of seedlings are which, simply by looking at the colour of the straw! So no surprises at flowering time. It is also saving money, ie fewer labels needed & the effort of recleaning them at the end of a season. J.