The mammals of the National Park area also include various species of squirrel, mice, vole, and gophers, as well as yellow-bellied marmots and North American porcupines. Carnivorous mammals consist of coyotes, red foxes, gray foxes, American black bears, raccoons, martens, fishers, ermines, long-tailed weasels, minks, wolverines, American badgers, western spotted skunks, striped skunks, North American river otters, cougars, and lynxes such as bobcats. Elk, mule deer, and pronghorns can also be found, though more frequently during the summer season. Bird species in the Crater Lake National Park area include various biological families. Common bird species include hairy woodpeckers, great horned owls, blue grouse, common ravens, dark-eyed juncos, mountain chickadees, red-breasted nuthatches, brown creepers, Clark's nutcrackers, and Canada jays, which are visible throughout the year; American kestrels, northern flickers, golden-crowned kinglets, Cordilleran flycatchers, Steller's jays, western tanagers, Swainson's thrushes, hermit thrushes, American robins, and rufous hummingbirds that frequent the area in the summer season; and mountain and western bluebirds in the fall and summer. Olive-sided flycatchers and chipping sparrows are common during the spring and summer seasons, while yellow-rumped warblers, pine siskins, and Cassin's finches can frequently be seen during spring, summer, and fall. In the early 20th century, Bull trout were present in many streams and river throughout the National Park area, particularly the Sun Creek and lower Annie Creek areas. Locals began stocking streams with non-native trout populations, forcing Brook trout to compete for resources and leading to their local extinction in Annie Creek, along with a significant decline in Sun Creek by the end of the 1980s. By 1992, Crater Lake National Park initiated a bull trout conservation project, removing invasive fish populations with electrofishing, snorkeling, and introduction of the toxin and inhibitor of cellular respiration antimycin A. They also created small barriers to keep new trout from reaching Sun Creek. In 1999, Bull trout were considered a "threatened" species by the Endangered Species Act, though locally, there are now about 2,000 Bull trout in the stream, almost ten times as many as the low point for Bull trout abundance at just 200 fish.