The headwaters of California’s Sierra Nevada provide important resources for wildlife and humans alike and are increasingly imperiled by climate change and other human-induced stressors. The introduction of non-native fishes into these historically fishless waters has profoundly restructured the aquatic food web, resulting in lower invertebrate diversity and the endangerment of endemic taxa such as the mountain yellow-legged frog (Rana sierrae/muscosa). However, the extent to which the effects of trout introductions cascade into the terrestrial environment is poorly understood even though these habitats are tightly linked. We quantified avian community composition, diversity, and overall abundance at fish-containing and fishless lakes in the southern Sierra Nevada for four years (2014, 2015, 2016, and 2020). We documented a change in avian beta diversity between fish-containing and fishless lakes, driven largely by turnover, as well as a decrease in overall avian abundance at fish-containing lakes approaching statistical significance. A fish eradication project at one lake between 2016-2019 allowed us to conduct a BACI (Before, After, Control, Impact) case study to assess changes in the avian community following fish removal. We report a two-fold increase in overall avian abundance at the fish-removal relative to the control lake, including the detection of two insectivorous bird species that were not detected at any previous surveys at that lake. Our results highlight the importance of considering aquatic and terrestrial habitats as interdependent systems and further motivate the conservation of fishless lake habitat in the Sierra Nevada’s alpine waters.