Methods
Study sites All fieldwork was conducted over April-June of 2014-2016. Ants and birds were studied at the moist subtropical broadleaved forests at low elevations in Chapramari Wildlife Sanctuary (26.8858°N, 88.8341°E, ~ 200m) in West Bengal, India. Bird diets were studied at Chapramari and in the temperate broadleaved cloud forests at the mid-elevation site of Neora Valley National Park (27.0611°N, 88.7707°E, ~ 2000m) in West Bengal. Bird diets were also studied at 1200m elevation in Neora Valley National Park (27.03°N, 88.78°E) and at 2300m (27.42°N, 88.20°E), 2700m (27.43°N, 88.19°E), 3200m (27.45°N, 88.17°E) elevations in Khangchendzonga National Park in Sikkim, India.