The Annual Sunstainable Redmond meeting last Monday was very informative. Gary Smith, Trout Unlimited salmon advocate, WaterTender, and city parks commissioner reported on factors affecting and indicating in-stream habitat health. His talk focused on the presence of salmon, birds and benthic invertebrates (bugs) as being environmental indicators. Gary reported counts of juvenile Coho and Chinook salmon have decreased for two consecutive years and the spawning Chinook salmon in Bear and Cottage Creeks, combined, have decreased for three consecutive years. He referenced to Micheal Hobb's research demonstrating river health clearly matters to birds. (Mr. Hobb's "Marymoor Park Sightings blog" is HERE.)
Below, are Mr. Hobb's comments about the relationship between the behavior of birds and in-stream habitat health:
"River health clearly matters to birds. The most obvious species that is effected by polluted water around here is the American Dipper, as they feed pretty much entirely on benthic invertebrates. If dippers are breeding on a stream, you know the water is full of benthic invertebrates, and the water is clean. Dippers poke around the rocks looking for things like stonefly larvae. They are the coolest birds, being ordinary songbirds (dippers are closely related to wrens), that have learned how to swim and dive. Read More >>
There are other birds that depend heavily on benthic invertebrates as well. Harlequin Ducks come to mind. While they winter in oceans, they breed in mountain streams such as the Teanaway. While they do eat some fish, they mostly dive into the streams to eat insects and other invertebrates. Spotted Sandpipers are another species, working stream edges and eating insects, insect larvae, worms, etc. And then, of course, there are the swallows and songbirds of riparian areas that eat things like mayflies and midges that emerge from the water.
Herons and kingfishers need two things: one is an abundance of small fish to eat, and the other is water clarity, since they hunt visually. This is true also of the mergansers – diving ducks specialized for catching fish. They often swim on the surface with their faces in the water, scanning for fish beneath them. Polluted waters are often lacking in fish, and while you may still find a heron or kingfisher there, searching, they will eventually give up and fly elsewhere if they don’t actually find fish. Birdwatchers definitely have found that some streams, ponds, and lakes have very few water birds. Pollution is presumed to be a likely cause.
Storm surges often cause high turbidity which greatly limits visibility of prey. You’re unlikely to see herons , kingfishers, and mergansers working a muddy, clouded stream. These fish-eating birds can simply fly to another location with better visibility, of course, but if they are nesting at the time, that means longer flights between foraging and the nest. It can mean they bring fewer fish back to their babies, due to commute times.
Adult ducks are not in much physical danger from flash stormwater events, as they can fly. But the timing of a flash flood event can matter. Many ducks nest along stream shores, in April-June typically. Flood events during this period obviously can destroy nests and drown ducklings. Even the adults might be at risk, since ducks molt all of their flight feathers at once, usually around the time of nesting, or shortly afterwards. While they can still fly short distances (or hop long distances), their mobility is limited. They also may be frantically trying to save their young, and the adults could then get caught up in floodwaters.
Just a further note, spawning salmon are a direct food source for many birds, though in ways that might surprise some people. Many birds eat salmon eggs. I’ve seen Mallards walking up the stream gobbling down fresh salmon eggs like they’re candies. I expect any other ducks that happen to be in spawning streams will do the same. Dippers and Spotted Sandpipers (and other shorebirds) will also eat salmon eggs. But more surprising to me is that many, many species will eat the flesh off rotting salmon carcasses. This certainly includes eagles and gulls, but also includes Mallards and other ducks and geese. And I seem to recall some songbirds taking a bite or two. Who can say no to salmon pate?
And then, of course, the spawned-out salmon carcasses provide food for the benthic invertebrate that in turn are the food for the salmon smolts, as well as for the Dippers and Harlequins."