small stands of old-growth Douglas fir and western redcedar (Thuja plicata), mostly within long standing privately held property. In the highlands one also finds grand fir (Abies grandis), western hemlock (Tsuga heterophylla) and other subalpine trees. The San Juan Islands host the greatest concentration of bald eagles (Haliaeetus leucocephalus) in the contiguous United States. Great blue herons (Ardea herodias), black oystercatchers (Haematopus bachman), and numerous shorebirds are found along the shore and in winter, the islands are home to trumpeter swans (Cygnus buccinator), Canada geese (Branta canadensis) and other waterfowl. Peregrine falcons (Falco peregrinus), northern harriers (Circus cyaneus), barred owls (Strix varia) and other birds of prey are found. In addition diving birds such as rhinoceros auklets (Cerorhinca monocerata), pigeon guillemots (Cepphus columba) and endangered marbled murrelets (Brachyramphus marmoratus) frequent the surrounding seas. Western bluebirds (Sialia mexicana), which were eliminated from the islands 50 years ago because of competition for nesting sites by non-native European starlings (Sturnus vulgaris), were recently restored to San Juan Island thanks to the efforts of volunteers and conservation organizations. The islands are famous for their resident pods of orcas (Orcinus orca). There are three resident pods that eat salmon, but also some transient orcas that come to take harbor seals (Phoca vitulina). Other marine mammals include river otters (Lontra canadensis), Steller sea lions (Eumetopias jubatus), common minke whales (Balaenoptera acutorostrata), Dall's porpoises (Phocoenoides dalli) and other cetaceans. Columbia black-tailed deer (Odocoileus hemionus columbianus) are the largest mammals on the San Juan Islands, which are unusual in their historic absence of large carnivores, except for wolves (Canis lupus) which were extirpated in the 1860s. Dr. Caleb B. R. Kennerly, surgeon and naturalist, collected a wolf specimen on Lopez Island, which is now in the National Museum of Natural History, probably during the Northwest Boundary Survey from 1857 to 1861. Also, there is a specimen of elk in the Slater Museum of Natural History at the University of Puget Sound that was collected on Orcas Island, and old-timers report finding elk antlers on both Lopez and Orcas Islands. Before 1850, most of the freshwater on the islands was held in beaver (Castor canadensis) ponds, although the aquatic mammal was extirpated by Hudson's Bay Company fur stations at Fort Langley and San Juan Island. Remnants of beaver dams number in the hundreds across the archipelago. Gnawed stumps and beaver sign are now seen on Orcas and other islands,