Natural Connections: 'Catching Crayfish in the Creek"

Natural Connections: 'Catching Crayfish in the Creek"

A small stream tumbled and crashed through edge of Bellingham, WA. The rocky ravine it had carved over time now provides refuge for big trees, a fish hatchery, a cacophony of birds, and humans, too. Well-worn dirt paths gave testament to the popularity of this waterfall-filled neighborhood greenspace. 

I was out for one last walk before packing my bags and boarding the ferry to Alaska. A great blue heron hunting above the first cascade allowed me to stalk it with my camera. Pacific wrens and towhees chattered from the bushes and wild roses bloomed along the trail. 

At one point I peeked down a side path leading toward a bridge. An older couple and their golden retriever were standing there chatting, and while I wanted to see the view, I didn’t want to disturb them. Catching my eye, though, they waved me over. 

“There’s a barred owl hunting crayfish in the creek,” exclaimed one in a stage whisper. “We’ve seen him here almost every day,” added the other. As if to confirm this fact, the brown and white checkered owl swooped off its perch on the lower branch of an alder tree. After dragging its talons through the water, the owl landed among the ferns and mosses on a low rock in the edge of the creek. From this new perch it turned its back on us and stared intently into the water. For a forest bird, it was extremely well camouflaged against the dappled light of the riffle. 

Then  whoosh  again, the owl flapped and skipped across a few feet of shallow water and came to rest on a bigger rock just downstream. Immediately it started picking at something in its talons. By zooming in on its beak with my camera, and then zooming in on the photo on my LCD screen, we were able to positively identify its meal as a crayfish. 

Although barred owls’ stereotypical diet of focuses on mice, they are actually very adaptable opportunists. Small mammals (including mice, but also shrews, voles, and flying squirrels) make up the bulk of their winter fare, but in summer they expand their buffet to include birds, insects and spiders, amphibians, reptiles, earthworms, fish, snails, and crayfish. 

Not every individual makes all of those options are part of its diet. Like flamingos, some barred owls eat so many crayfish that their belly feathers take on a pinkish hue. (I never thought I’d compare owls to flamingos!) Barred owls in the Eastern Cascades seem (based on surveys of their pellets) to subsist mostly on beetles, with frogs and flying squirrels for dessert. One owl was observed feeding almost entirely on aquatic snails. What they eat is largely dependent on what’s available at the time in their habitat. These birds don’t migrate, so they have to muster a year-round food supply from their local territory. 

Needing big, old trees to nest in, barred owls were once confined to relatively undisturbed forests in the east. The advent of fire suppression in the northwest, along with tree planting across the Great Plains during the last century, gave the owls a path for hopscotching their way into a much bigger range. Their map now encompasses the southern provinces of Canada, southeastern Alaska, British Columbia, Washington, Oregon, and northern California.

Throughout their expansion, having an adaptable palate has worked to barred owls’ advantage. By eating oddities like crayfish they can scrape by even in small fragments of forests—like this creek ravine surrounded by neighborhoods. 

All of this is wonderful for the barred owl, but not for their cousins the spotted owls who are native residents of the barred owls expanded range. Spotted owls were protected under the Endangered Species Act in 1990 because habitat fragmentation due to logging had reduced their nesting habitat. Spotted owls are smaller, less aggressive, and more set on eating flying squirrels, wood rats, and mice. With the influx of barred owls, their plight is only getting worse. Not only do barred owls outcompete them for food and nesting habitat, they also hybridize with spotted owls and dilute their gene pool. The best hope for rarer owls’ continued survival is the protection and expansion of old growth forests to provide enough habitat for the two species to coexist.

I’d learned about this conflict back when I worked in the redwoods of Northern California, so my excitement at watching a barred owl hunt in broad daylight was tempered by unease over the situation. The behavior we witnessed from that bridge is exactly why barred owls are a problem for spotted owls. We could declare this a normal consequence of species expansion and competition. Surely this scenario has played out millions of times over the eons. Natural selection is all about picking winners. This feels more dubious to me, though, because humans were definitely involved in changing the parameters. 

Change is constant no matter how much we humans are involved. There’s value in working to protect things as they were, but finding beauty and wonder in a changed world isn’t wrong either. 

The owl caught three more crayfish while we watched. Then, in a silent flash, it swooped out of the ravine through a gap in the sun-drenched leaves.

Last Update: Jun 11, 2018 2:16 pm CDT

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