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:The extirpation of ground squirrels from the boreal forest (Gillis et al. 2005; Donker and Krebs 2011), poor active-season survival, low recruitment rates, immigration from nearby low elevation-meadow habitat and population growth rates <1.0 provide convincing evidence that the boreal forest…
Category: