Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:An understanding of the roles of food availability, vegetation cover, grazing intensity and burning on bird nesting success across management types (Little et al. 2013) bring us closer to understanding the overall effect of farming practices on birds in the system as compared to the conservation…
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