Rigor Vitae: Life Unyielding

Monday, April 24, 2006


Here on the west slope of Utah's Wasatch Mountains, the burgeoning human population has affected wildlife in many ways. Some species have been losers, others have been winners. Part I of this post was devoted to a loser, the Long-eared Owl (Asio otus), a species that appears to be particularly vulnerable to the ravages of a big winner, the Raccoon (Procyon lotor).Since writing part i, I took a couple of moonlight cross-country ski trips through the habitat where these birds like to nest in clones of Gambel's Oak (Quercus gambelii). In this open country, it is easy to listen for Longears while keeping a good distance from potential nest sites. In the more rugged country where they nest in Bigtooth Maples (Acer dentifolium), it's harder to check on them this early without disturbing them. I watched a hunting Longear the other night, and heard a pair courting a couple of weeks ago. Sadly, I also saw two Raccoons in the vicinity that same night, so my hopes for their nesting success are modest.

Since taking a sabbatical from falconry in the early '90s, I haven't spent much time in the open marshy habitat favored by the Longear's cousin, the Short-eared Owl (A. flammeus), and can't speak to its current status in this area, nor can I say much about Pygmy Owls (Glaucidium gnoma), which have always appeared to be rather uncommon around here. Unlike the misanthropic Longears, the successful Great Horned Owls (Bubo virginianus), Screech Owls (Otus asio) and Barn Owls (Tyto alba) don't mind having humans around. All three species are doing well here, and nest commonly right in Salt Lake City. Burrowing Owls (Athene cunicularia) have suffered a population drop recently, but I think this can be attributed to a drying trend over the past two decades, causing a steep decline in vole (Microtus spp.) numbers. Unable to find sufficient voles to feed on, Badgers (Taxidea taxus) have widened their menu preference to include the owls. I've never found Saw-whet Owls (Aegolius acacicus) in the city, but these birds don't seem to be otherwise picky about their habitat, and appear to be doing well in many areas.

The last local owl species is in many ways my favorite. The gregarious little Flammulated Owl (Otus flammeolus) lives in old mixed forests at high elevation. When I found my first Flammulated colony at age 13, the literature described it as one of North America's rarest owls, and I thought I'd found my ticket to ornithological stardom. Actually, in the proper habitat, they can be exceedingly common, they are just very hard to observe, as they normally stay more than 20 feet from the forest floor, where their beautiful black, white, gray and cinnamon plumage is usually obscured by thick foliage. Summer is short at the altitude these birds prefer, and their appetite for insect prey can only be satisfied during four months. The youngsters develop very quickly, and leave the nest, an abandoned hole of a Hairy Woodpecker (Picoides villossus) or Williamson's Sapsucker (Sphyrapicus thyroideus), at about three weeks of age. Unlike our other local owls, the Flammulateds actually fly some distance south for the winter.

Dependent as these birds are on old, dead standing trees, they have come into direct conflict with the ghastly subdivisions that seem to proliferate like cheatgrass up every draw. Unfortunately, such subdivisions spread within a mile of both Wasatch Flammulated colonies I knew. In a preemptive effort to protect their ostentatious investments from fire, the human residents cleared all the dead wood from the area, and the Flammulated colonies were annihilated. So far, discreetly placed nest boxes have remained unused, but I continue to experiment with different locations and designs. Today I built four new boxes with a slightly smaller aperture that I'll install later this week. I only hope that a lack of nesting sites is the only thing keeping the owls away. I fear that the tidying of dead wood may have reduced insect numbers below a point critical for the Flammulateds.
illustration: FLAMMULATED OWL (1990) acrylic 15" x 20"


Anonymous Anonymous said...

Another thought-provoking post! Makes me wish I had explored the Wasatch more when I was in Kemmerer.

A pair of burrowing owls has moved into the parking lot at my work. While I'm pretty sure they're safe from badgers I worry about cats, and raccoons for that matter.

10:53 PM  
Anonymous Anonymous said...

Funny that Neil should mention urban owls. We've had red-tailed hawks and ravens living here for years now, while great-horned owls and cranes drop in for a visit every now and then.

Any long-eared owls nesting in the city?

4:51 AM  
Blogger Carel Brest van Kempen said...

Neil: Thanks, Neil. You're in California, aren't you? I've seen urban Burrowing Owls in Florida, and it doesn't surprise me to hear of them in California. So far, I've seen them in agricultural areas here, but never in the city. Like Flammulateds, they tend to nest in colonies here.
Alan: Urban Ravens are pretty new here and Crows are very new. I wrote a post about this. I've never seen Longears in very close proximity to people. Especially when nesting, they're one of our shyest birds.

7:24 AM  
Anonymous Anonymous said...

It might be a push to call Davis "urban" though the ag-belt separating us from Sacramento is attenuating. Barn owls rule the night in Davis, its hard to go anywhere in town and not hear them, thanks at least in part to pervasive boxing.

Swainson's hawks are also very abundant though I think most of them forage in the ag fields outside Davis. Corvids (jays, magpies, crows) probably outnumber people here.

The burrowing owls are probably migrants from a small engineered "habitat" (complete with PVC burrows) set aside when the ranchland around our museum was converted to tract housing. Despite the small size of the allocation they seem reasonably content.

9:33 AM  
Anonymous Anonymous said...

Why were raccoons introduced? Accidentally?

In the area in North Carolina where the red wolf has been re-introduced one benefit noted is that the wolves are preying on raccoons, reducing their numbers, in turn reducing predation by the raccoons on the eggs of a turtle (I forget which one)species either endangered or threatened. Perhaps as the recovering gray wolf moves into Utah (if and when it does) the owls will get some relief.

6:56 AM  
Blogger Carel Brest van Kempen said...

Our raccoons are probably descended from escaped captives. That's interesting about the Red Wolves. We're already starting to get Gray Wolves in Utah. I hope they develop a taste for 'coon. With wolves around the coons are sure to be a bit less cocky, anyway.

8:23 AM  
Anonymous Anonymous said...

I see. The bird much prefers nesting sites away from noise and bustle that could mean danger to the young. When you consider the destructive curiousty of male human adolescents it makes sense.

I hope any attempt to preserve some nesting habitat succeeds.

1:09 AM  
Blogger Carel Brest van Kempen said...

Hi Alan. Your criticism is appropriate but probably exaggerated. It's a good idea to be aware of the impact of your own observation, and there were nests that I disturbed more than I should have as a kid. One good policy I developed early on is to stay away from bird nests before the eggs hatch.

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