My first two columns on the owls of Idaho covered a lot of the basic attributes of owls as a group. Over the next few columns, I want to look more closely at each of our fourteen species. Our owls differ in many ways, so there are a number of angles to take to figure out which species to address first, which second, and so on.
Factors I looked at were commonness, population size, range size, conservation need, body size, migratory category, taxonomic order, and even eye color. There are yet other attributes to use in sorting these species. Interestingly, each sort provides a different order or different grouping of species. This shows that these attributes are not highly correlated. I could have gone in alphabetic order, but that’s like not trying.
For example, by commonness, both the great horned owl and the northern saw-whet owl are classified (friendsofcamas.org) as “common, but sometimes difficult to find.” I love the qualifying, “sometimes difficult to find.” I think we can safely say that about all owls. Think about how many of these two species you have seen. I’ve never seen a saw-whet in Idaho compared with countless great horneds. This points out that commonness is not about what people see, but what count data suggest are out there.
By population size, the great horned owl wins again. Partners in Flight maintains a database of bird population sizes (pif.birdconservancy.org) that can be viewed in various ways. For example, you can see the total global population of a species or just the estimate for a particular state or Bird Conservation Region. The latter are large polygons that are based on ecology, not politics.
Partners in Flight estimates that there are 73,000 of these flying tigers in our state. But realize that owl populations are notoriously difficult to estimate because most of them are only out at night. Further, many of our forest owls are in mountain terrain where there are no standard bird census routes. Partners in Flight makes no estimate for flammulated owls, northern hawk owls, long-eared owls, boreal owls, or our “common” northern saw-whet owl for Idaho due to lack of data.
When we look at the size of the breeding range, we have to leave Idaho and look at the total range size for the species in North America. According to another Partners in Flight database (pif.birdconservancy.org), all of our owls have enormous range sizes. This attribute does not help place the species into a useful order. That also means that they are so widely distributed that we don’t need to worry about their futures simply based on the area they occupy. Species with large ranges are safer than species with small ranges.
By conservation need, I am also looking at the species at the scale of North America. None of our owls are in the highest category of need — the Red Watch List — as classified by Partners in Flight. That category includes species that are already classified as threatened or endangered, e.g., California condor, and those species that would be so classified if political interference didn’t block that action, e.g., greater sage-grouse. If you are hunting sage-grouse, stop.
But we do have a few species that fall into the next two risk categories. Flammulated owls are on the Yellow Watch List, where species populations are not declining, as far as we know, but they are under various threats. Snowy owls are also on the Yellow Watch List, but they have documented population declines along with various significant threats. That puts them in a higher risk category. Idaho can take conservation action for flammulated owls because so many nest here. But there may not be too much we can do about snowy owls, except to protect those few who show up here in winter. Most of the snowy owls, most of the time, are far north of here. Canada has the main responsibility for them.
I could order species by body size, but that’s sort of like alphabetical order — boring. Eye color is an interesting way to group owls. Eleven species have yellow eyes as adults, and only three have dark eyes. The latter include barn owl, flammulated owl, and barred owl. One website I found claimed that owls with black eyes hunt at night and those with yellow eyes hunt during the day. That’s obviously nonsense. Don’t believe everything you find on the web, in case you didn’t know. And in any case, that only sorts our owls into two groups. I need some sort of linear order.
Taxonomic order is always a solidly scientific way to proceed on almost any enterprise. I know the scientific method, and it’s enormously robust. Most of us don’t get an education on the scientific method, and that costs society enormously. I think it should be taught along with reading, writing, and arithmetic. Let’s add required courses in logic and probability. But that’s another story.
Unfortunately, taxonomic order has zero intuitive sense for the average person. Why are barn owls in a different family than all the rest of the owls in the world? There is a good scientific reason, but it doesn’t fit on a bumper sticker.
So, let’s go with commonness, not as classified by the Birds of Idaho Field Checklist, but rather by what you and I see as we run around the Idaho countryside. This order, too, will vary by where you live and where you go. I’ll claim some executive privilege and order owls by where I live and where I go. I’ll throw in a bit of my experience in our neighboring state of Oregon, where I spend some time in the spring and summer both birding and running Breeding Bird Survey routes. But eastern Oregon is very much like southwestern Idaho. I guess that’s why those counties want to leave that state and join us. Ecology can be so unifying.
So, loosely arranged by commonness, here we go. As I mentioned in an earlier column, I studied burrowing owls while working for the Bureau of Land Management in Shoshone, Idaho, from 1979 to 1985. I found hundreds of burrows occupied by these owls, either for nesting or just for hanging out. I could usually guess if a burrow had a nest because there would be a lot of animal and insect parts strewn about the burrow opening. Of course, once the young start to emerge, you know for sure.
But even without that experience, I’ve seen far more burrowing owls since we moved to Idaho in 1974 than any other species. I love sagebrush country, so I may spend more time in habitats suitable for burrowing owls than in other habitat types. Although I certainly don’t see this species on every trip down Mud Flat Road or crossing the Snake River Plain, I’m never surprised to find an owl somewhere.
Partners in Flight estimates that there are 2,900 burrowing owls in Idaho. Because this species is largely diurnal, the Breeding Bird Survey (BBS) has a chance of monitoring populations of burrowing owls along with sage thrashers, western meadowlarks, and other species in sage habitats. So, this estimate is probably reasonably good. At least it’s likely to be the most accurately monitored owl in Idaho. Short-eared owls are also picked up by the BBS. More on them later.
Like most owls, burrowing owls will eat whatever they can catch. In my study, I found plenty of feathers, mammal parts, frog legs, and other remains around the entrance to burrows. But what I found most fascinating were all the insects they ate. One way to examine owl diets is to collect the pellets they regurgitate, which contain undigestible materials — hair, feathers, bones, and teeth, for example. Most owl pellets are dominated by hair, and you have to break them apart to find the other stuff.
But burrowing owl pellets are often 100% insect parts. When you break them apart, you have what looks like a pile of glitter — tiny, often colorful bits that are much harder to identify than, say, mouse teeth. I’m sure that expert entomologists could figure out what species a lot of the parts are from. Sometimes you get an entire mandible or foot, and those are probably good evidence of particular species. One problem with these pellets is that they are very fragile. A good rain will break them up and wash them away.
The one insect species that I could identify and that I frequently found was the burying beetle, also known as the carrion beetle (Nicrophorus). There are six species in Idaho. This fascinating group of beetles locates carrion and then buries it where it will serve as food for young. You can imagine how these beetles are attracted to the animal debris in and around burrowing owl burrows, and how the owls can then readily gobble them up.
I’ll leave you with that image for now. Hope you already ate.