With the application of pesticides, a negative correlation will eventually develop between the amount of pesticides used and the availability of skylark food resources. As such, the food availability is considered to be a result of the chemical environment of the skylark breeding site. Nest site quality depends rather on the physical environment of the skylark breeding site. If it is assumed that the nest site quality can be measured in terms of the survival rate of eggs and nestlings and that survival can be expected to increase if the nest is located in suitable vegetation outside the arable fields, then nest site quality will be correlated with the availability of natural habitats in the agricultural landscape.