Friends of Oaks Bottom held its summer nature walk at the Bottom on Friday, July 11th. The refuge was a lush green oasis with swallows of several species diving and darting over the waters of Wapato Marsh snagging insects. Other summer residents included kingfishers, Canada geese, mallards, gadwalls, and wood ducks. We spotted a couple of bald eagles on a sand bar near Hardtack Island. There were several very active downy woodpeckers.
As most people now know, the water level on Wapato Marsh dropped suddenly this past winter. The beavers are gone, and thus the beaver dam that has been keeping levels constant since 2018 is in disrepair, allowing the pond to drain. A couple of dead beavers were seen in the winter, and there is still one desiccated corpse by the water’s edge. Water levels are expected to drop further during the course of the summer. A sign already warns of HABs (hazardous algae blooms) that have become common in summer months. We observed a wash of cyanobacteria (blue green algae) at the entrance of the big culvert to the Willamette.
With the drop in water level, mud flats were exposed in winter. These are now fully vegetated. One plant that has returned, unfortunately, is the purple loosestrife. A few years ago, Galerucella beetles were introduced to contain the plants. Ecologists hope that remaining beetles will deal with the new loosestrife population.
Another plant that has made a comeback with the return of the mudflats is leafy beggars-ticks (Bidens frondosa). The beggars-ticks is now three feet tall and will begin blooming in August. The flowers are not showy; in fact, they are rayless members of the composite family. Beggars-ticks, named for its barbed achenes that cling to passing mammals, is a favorite food of the muskrat.
As usual, we used up our three hours before returning to Sellwood Park. Look for an announcement in the fall for that season’s nature walk!
