The tree squirrel about the Lake is the pine squirrel or "chickeree.".    From Wordnik.com.  [The Lake of the Sky Lake Tahoe in the High Sierras of California and Nevada, its History, Indians, Discovery by Frémont, Legendary Lore, Various Namings, Physical Characteristics, Glacial Phenomena, Geology, Single Outlet, Automobile Routes, Historic Towns, Early Mining Excitements, Steamer Ride, Mineral Springs, Mountain and Lake Resorts, Trail and Camping Out Trips, Summer Residences, Fishing, Hunting, Flowers, Birds, Animals, Trees, and Chaparral, with a Full Account of the Tahoe National Forest, the Public Use of the Water of Lake Tahoe and Much Other Interesting Matter] Reference

"Cheep, cheep, chickeree," sang one bird to another.    From Wordnik.com.  [Nine Little Goslings] Reference