Northern spotted owl (female). Photo by K. Perensoviche. Wikimedia Commons
(Click on the following link to listen to an audio version of this blog … Spotted Owls and Barred Owls
I remember the conflict very well. The back and forth in the late 1980’s of charges and countercharges between logging interests of the Pacific Northwest and ecologists and environmentalists from all over the country. The debate: should the logging of the old growth forests of the Northwest be halted to save habitat for the northern spotted owl (Strix occidentalis caurina)? It was a vicious debate.
I had a biology colleague who stated emphatically that since the northern spotted owl was “just” a subspecies (with two other subspecies that were not, at that time, under threat of extinction) the Endangered Species Act didn’t apply to it. I am not sure how he reasoned that out exactly, but I think that his fundamental political point of view was bubbling up through his loose grasp of the biological facts and logic. The Endangered Species Act clearly states that any species or subspecies that is in decline may be considered for Act listings and protections.
Anyway, in 1990, the northern spotted owl was placed on the endangered species list, and in 1991 a sweeping federal judge’s ruling removed 24 million acres of federally controlled land from possible logging. In effect, this ruling ended timber harvesting in the Northwest (an activity that had been in decline for years). The spotted owl’s habitat was saved. It has been said that no other single animal species has had such a huge impact on land use, environmental policy and economics.
California spotted owl. Photo by USFWS. PUblic Domain
The three subspecies of spotted owl are distributed across the western edge of North America. The northern spotted owl is found primarily in the mature forests of British Columbia, western Washington, Oregon and down into the mountains of northern California. The California spotted owl (S. o. occidentalis) is found in the southern Cascades and western Sierra Nevada mountains and in isolated mountains down through California to Baja California. The Mexican spotted owl (S. o. lucida) is found in the southwestern United States (Utah, Colorado, Arizona and New Mexico) and western Mexico
Mexican spotted owl. Photo by G. Smith. Flickr
In the intervening 35 years the California and Mexican subspecies of the spotted owl have both declined precipitously primarily due to habitat loss. The Mexican spotted owl is now also listed as “threatened,” but the California spotted owl has not yet gained any official extinction designations.
The northern spotted owl is a medium-sized owl. It is 16 to 19 inches long and weighs from one to just over one pound. Its wingspan is 42 inches. In the northern-most part of its range, it is found in a very
Northern spotted owl. Photo by BLM. Public Domain
specific type of habitat: old growth forests especially old growth at relatively high elevations. It is considered one of the indicator species of old growth forest ecosystems! In the southern sections of its range, this habitat specificity is less narrow and these owls can be found in mixed forests although still primarily at higher elevations. The northern spotted owl’s diet is also extremely specific. It eats small mammals (90+% of its diet) especially northern flying squirrels (Glaucomys gabrinus), wood rats (Neotoma fuscipes and N. cincera), red tree voles (Arborimus longicaudus), western red-backed voles (Clethnonomys californicus) and gophers (Thomomys spp.).
The setting aside of what was left of the old growth forests of northwest was at first thought to be sufficient to provide the northern spotted owl with enough space and resources to survive. Further fragmentation of these pieces of old forest, though, and their significant loss due to wildfires have made this simple picture look untenable. Also, the impact of a second owl species, the barred owl (Strix varia) has greatly complicated the survival model for the northern spotted owl).
Barred owl. Photo by P. Burian. Wikimedia Commons
The barred owl is the second most abundant and the second most widely distributed owl in North America. Only the great horned owl (Bubo virginianus) is more numerous and has a more extensive North American range. The barred owl is 16 to 25 inches long with a wingspan up to 49 inches. Male, barred owls weigh in between 1.3 and 1.5 pounds and females barred owls are 1.7 up to 2.5 pounds. The barred owls, then, are substantially larger than spotted owls.
The barred owl is native to eastern North America and is especially found in mature, eastern forests. It eats a very wide range of prey including numerous small mammals (its preferential food), but also readily takes small birds, amphibians, reptiles, bats, large insects, earthworms, fish and crayfish.
Distribution of barred owl. Map by Cephas-Mazur and James. Wikimedia Commons
There is an interesting, westward extension from the barred owl’s eastern range that seems to loosely follow the riparian forests and, possibly, human planted trees and wood lots that dot the former, northern prairie from western Ontario across Manitoba, Saskatchewan and Alberta all the way over to British Columbia. Within this expansion corridor, barred owls have been observed for over 150 years. In the vast, old growth forests of British Columbia the barred owl found an idea, forest habitat and, because of its larger size, aggressive nature and ability to take such a wide range of food, has out-competed many other owl species including the northern spotted owl.
Observations on these western barred owls has shown a number of behavioral differences between them and the eastern forest barred owls. These western barred owls do not preferentially inhabit dense, old growth forests. They are frequent residents of secondary and even fragmented forests. These western barred owls are also preferentially found near water. Lower elevation, riparian forests are their primary habitats. Further, genetic analysis of these western barred owls indicates that they have been separated from the eastern barred owls for thousands of years, not the few hundred suggested by the human-assisted irruption hypothesis. There is some doubt, then, about the validity of the barred owl being classified as an “invasive species” in these western forests. They may have been living in these forests for centuries.
Jennifer Ackerman in her book What an Owl Knows describes the interactions between northern spotted owls and barred owls. The very territorial barred owls zero in on the calls of the spotted owls and physically, sometimes lethally, interact with them. In the northern sections of the spotted owls range where the barred owls numbers are quite high, the spotted owls call to each other less and less. It is like they are hiding from the barred owls. In the middle and southern regions of the spotted owls range, though, where the barred owl densities are relatively low, the spotted owls continue to call to each other and, in the words of one of the scientists studying these owls, “seem to have decided to put up a fight for their territory.”
The U. S. Fish and Wildlife Service (FWS) has the legal responsibility to protect endangered species like the northern spotted owl. Ten years ago, the FWS killed 3600 barred owls in an attempt to reduce their influence on the northern spotted owl population. The FWS describes the outcome of this lethal experiment as “slowing down but not stopping” the barred owl mediated decline in the northern spotted owl.
Barred owl. Photo by L. Koester. Wikimedia Commons
In November, 2023 the FWS published a new plan in which they proposed to kill 500,000 barred owls over a three decade time span in order to ensure the survival of the northern spotted owl and the California spotted owl. Reactions to this proposal from scientists and the public have been overwhelmingly negative.
Is it ethical to kill one species to possibly save another? Is this barred owl extermination plan even possible? Wouldn’t removing barred owls from one part of a forest just result in the influx of barred owls from adjacent habitats? How long would this slaughter of barred owls have to go on to generate a safe space for the spotted owls?
There are some owl specialists who feel that the habitat selection preferences of the northern spotted owl (high elevation, mature forests) and the barred owl (lower elevation, riparian forests) should be explored to try to keep the two species apart. Further, some experts are questioning the classification of the barred owl as an “invasive” species in the Pacific Northwest based on genetic data of these western owls. After how many years of residence does a migrating species become “native?”.
A final proposal on the barred owl/spotted owl problem is expected this summer.