in the dry climate; in the absence of periodic fires they tend to displace grasses and sagebrush and to create relatively barren landscapes. The Park Service is considering controlled burning to limit the junipers and to create open areas for bunchgrasses that re-sprout from their roots after a fire. Wildflowers, which bloom mainly in the spring and early summer, include pincushions, golden bee plant, dwarf purple monkey flower, and sagebrush mariposa lily at the Painted Hills Unit. Munro's globemallow, lupines, yellow fritillary, hedgehog cactus, and Applegate's Indian paintbrush are commonly seen at the Clarno and Sheep Rock units. Fauna Birds are the animals most often seen in the monument. Included among the more than 50 species observed are red-tailed hawks, American kestrels, great horned owls, common nighthawks, and great blue herons. Geese nest in the park each summer, and flocks of sandhill cranes and swans pass overhead each year on their migratory flights. California quail, chukar partridges, and mourning doves are also common. Others seen near the Cant Ranch and the visitor center include rufous hummingbirds, Say's phoebe, yellow warblers, western meadowlarks, and American goldfinches. Visitors on trails may encounter canyon wrens, mountain bluebirds, mountain chickadees, black-billed magpies, and other birds. Large animals that frequent the park include elk, deer, cougar, and pronghorn. Beaver, otter, mink, and raccoons are found in or near the river. Coyotes, bats, and badgers are among the park's other mammals. Predators hunt smaller animals such as the rabbits, voles, mice, and shrews found in the park's grasslands and sagebrush-covered hills. Bushy-tailed woodrats inhabit caves and crevices in the monument's rock formations. Bighorn sheep, wiped out in this region in the early 20th century, were reintroduced in the Foree Area of the Sheep Rock Unit in 2010. Many habitats in the monument support populations of snakes and lizards. Southern alligator and western fence lizards are common; others that live here include short-horned and common side-blotched lizards and western skinks. Garter and gopher snakes and western yellow-bellied racers frequent floodplains and canyon bottoms. Rattlesnakes, though venomous, are shy and usually flee before being seen. The springs and seeps in the park contain isolated populations of western toads, American spadefoot toads, Pacific tree frogs, and long-toed salamanders. A 2003–04 survey of the monument found 55 species of butterflies such as the common sootywing, orange sulphur, great spangled fritillary, and monarch. The monument's other insects have not been completely