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:MacLeod, personal communication) in a small, isolated mountain range (Cerros del Sira) in Huánuco department (Herzog and Kessler 1998; MacLeod et al. 2006; BirdLife International 2011d; Gastañaga Corvacho et al. 2011). Gastañaga Corvacho et al. (2011) presented evidence for elevating both subspecies to species rank, which is followed here.
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