FIELD NOTES   The 12-mile float from the Lower Skilak Lake boat launch downstream to Bing’s Landing traverses the wild middle stretch of the Kenai River. Almost half a million salmon spawn annually in the broad, meandering channel in the first four miles downstream from the lake outlet. Watch for the swirls and wakes of churning fish, especially in shallow gravel flats. This feast of protein draws out brown and black bears, especially sows with cubs, making this a potentially dangerous place to explore on foot in the fall and early spring. Lynx, river otters, coyotes, wolves and mink also venture out, particularly at night when fishing boats are off the river. In early winter and spring, open water draws 50 to 100 trumpeter swans—and similar numbers of bald eagles—to the sweeping oxbows downstream from the lake. During summer, bald eagles and ospreys scan for meals from overhanging trees. There are several active eagle nests in large cottonwoods, easily viewed from a boat. Loons and other waterfowl nest along the banks and large family groups paddle together in mid-summer. Watch for flocks of seed-seeking white-winged crossbills in the spruce tops. Bank swallows and belted kingfishers burrow their nests into the exposed dirt cliffs. Watch for Arctic terns in early summer and shorebirds through August.