Fig. 1

a Map illustrating the distribution of all three Metallura tyrianthina subspecies that occur in Peru. Circles denote sampling sites for both genetic and bill length data; squares represent sampling sites for bill length data only. Blue points are sites where the habitat was characterized as humid montane forest and brown points semi-humid montane scrub. b Map of sampling sites from the department of Cusco, Peru. One pair of sites was from the humid (Carrizales) and drier (Urubamba) sides of the Cordillera de Vilcanota, separated by ~20 km. A second pair of sites was along the Manu Road, with a humid (Pillahuata) and drier (Paucartambo) site ~5 km apart. c Topographic profile of the Cordillera de Vilcanota, which exceeds 5000 m, and the Manu Road where a cordillera less than 4000 m in elevation separates the two sites along the Manu Road