Earth & Sky

The following person was interviewed for today’s program. Our thanks to:

R.J. Gutierrez
Professor and Gordon Gullion Chair in Forest Wildlife
Department of Fisheries and Wildlife
University of Minnesota
St. Paul, MN

Interview with Rocky Gutierrez:

ES: Thanks for talking with Earth and Sky today. Can you give me a little background into the research you’ve been doing lately with Spotted owls?

RG: I started working on spotted owls in 1980 and primarily, worked with graduate students, each of whom conducted an independent research project under my direction. And over that time, we started with the Northern spotted owl, and expanded to the California spotted owl, and then to the Mexican spotted owl, which are all three subspecies. And, our intent – at least my intent – of starting this research program, was to build a foundation of scientific knowledge upon which we could develop plausible, or reasonable management plans to both protect the owl and also to allow some judicious logging to occur. My research projects have now been going on for essentially twenty-four years. So it’s been quite a monumental effort. I’ve had about 30 graduate students that have gotten degrees under my direction.

Getting back to your earlier question, the two areas that scientists are focusing most on with the spotted owl, including all three subspecies, are population dynamics and habitat selection. The former, the population dynamics, scientists, and also the public, the people who are interested in logging or protecting owls, they’re interested in, what is the status of the population? Is it stable? Is it increasing, is it decreasing? And so, this is a scientific question in a sense, as well as a management-monitoring question for those agencies involved in protecting the owl. And so those scientists have been engaged in almost two decades now in trying to understand, what are the population dynamics of these owls? What’s their rate of reproduction, what’s their rate of survival, and whether the combination of those two leads to a stable population. So there’s been a huge amount of work that’s been done on those two areas. And, it also turns out to be an enormously complex problem, because when one looks across all three subspecies, they inhabit somewhat different habitats depending on which sub-species you’re talking about. And, they’re also influenced by different kinds of weather patterns. So, you have not only the inherent difficulty of working with a species that’s nocturnal, that’s in low numbers, and therefore – they’re not difficult to find but there’s not very many of them – so you can’t work with large numbers of individuals to get a good sample. But you also have this complexity of different habitats, different vegetation, different forest types that they inhabit, as well as different kinds of weather patterns that affect them. Like in the West Coast, you have winter rainfall and snow, and then there’s a drought in the summertime. Whereas in the Southwestern United States, you have both winter precipitation and then you also have the summer months, which just makes it very different in terms of how owls respond in the Southwestern United States compared to the West Coast.

The second thing that scientists are focusing on is the habitat requirements of the owl – not only just what habitats they use, but what do they actually need to survive. And that latter question is very important for me, as an applied scientist, because I feel one of the charges of the applied scientist is to try to understand how we can use some resources and still maintain these owls so that they don’t go extinct. Many people have studied habitat selection and tried to understand the requirements of the spotted owl. In fact, there was a recent study done by a European on habitat selection on all raptor species in the world, raptors being birds of prey. And, he found out that there were more scientific papers published on the study of spotted owl habitat than any other bird of prey in the world, which I think is a pretty amazing statement, considering that we’ve only been interested in the status of this bird for about three decades.

So, those are the two primary areas of interest that scientists have been focusing on. And, my students and research associates have been focusing on those two issues.

Now there’s a third issue that we’ve been interested in, here in my lab, and we’ve collaborating with the American Museum of Natural History, with Dr. George Barrowclough, and his research crew, on the genetics of spotted owls. And that is, we’re trying to understand what the evolutionary history is of these birds, how closely are they related in terms of individual subspecies, as well as the relationships between the different populations. Which population might have been the progenitor for the other population through dispersal, and what is the gene flow between different populations and what is the genetic variation in these populations. Because all of those issues are important and of interest to people who are concerned about spotted owls.

So I think I’ve hit some of the highlights of the general questions that you brought up, and we can talk about more of the specifics if you want.

ES: Let’s start with the populations of Spotted owl.

RG: The dynamics of the spotted owl, it turns out that this is a complicated problem, and one in which people want answers right away. But when you deal with an animal that’s relatively long-lived, where they live anywhere from 10 to 20 years in the wild, and we actually have one female who was at minimum 24 years old when she finally disappeared this year. That’s a long time to try and understand what’s happening to a population, because there isn’t a great deal of turnover. If you were studying mice with a lifespan of 1-2 years, then you’d get these generation times which are very short, where you can mark a lot of individuals to find out how fast they disappear from a population, and how fast they re-colonize, and so forth. But with spotted owls, you have to wait a long time before one dies and is replaced by another one, and so on and so forth. Because they’re nocturnal, they’re not always the easiest birds to find. Their low-density makes it less efficient in finding them, because you have to move some distance between each pair to locate them, as opposed to many other species of owls. For example, the Tawney owl in Europe, which is in the same genus, and has been studied a great deal by Europeans. The single spotted owl territory – the area that a single spotted owl lives in, or a pair lives in, would hold about twenty to thirty tawney owls. So you can see that their density is much lower than even members of their own genus. And, those facts make it difficult for us to understand how their rate of survival is, and their rate of reproduction. The other thing that’s important is, that because they’re in low numbers, we have to have huge areas of study before we can get a sample of birds that’s large enough to make strong statements about what their survival is. In other words, if you only have a sample of five individuals, you really can’t estimate their survival rate very well, because there are just not enough individuals to have confidence in the results of the calculations. And so you have to have a fairly large sample of birds, and this requires huge areas. Our study areas are on the order of 100,000 to 300,000 thousand acres in size – so they’re very large areas, and in those areas there’s only 70 pairs of owls. So, you have gigantic areas with fairly low number of owls. But you have to be able to find these owls every single year, and then mark them, and find out whether they survived or not. But having said that, we can say that the techniques that have been worked out for studying spotted owls have been quite successful. The good thing about working with spotted owls is that they’re relatively tame, and they’re easy to locate. They respond easily to imitations of their calls. And, their calls are easy to reproduce. I could actually do that if you want to hear one.

If one were going to study these birds, what we do is that we have a big area, and we survey this area during the daytime to find out where there are good locations that allow us to project our voice over a broad area. For example, we either walk down a trail or cross-country, or on a road, and find a ridge or a point of land that overlooks a large canyon, that way our voice will project over a big area. And then we mark this, and we come back at night, and imitate the call of a spotted owl there for ten minutes. And then we go to the next point, and then the next point, and so on. And we do this over very large areas, at least twice and sometimes three times a year to try to detect a bird. And when we get a detection at night, we come back during the daytime and try to elicit a response from the bird that we heard the night before. And when we hear it during the daytime, we run toward the sound and keep doing this until we visually sight the bird. And when we sight, we can capture it by fooling it with a mouse, thinking it’s a prey, in front of it, and they’ll come down to try and get the mouse, and then we can catch them with a net or a noose, and so forth, but the sound of a spotted owl is basically a four note hoot, it sounds like this – . And we do this repeatedly every few seconds

And then you listen for them to respond. You mark the location on the map, and then come back in the daytime so you can see where you’re going – sometimes we catch them at night.

It varies, by individual, and by how close they are, and what their reproductive condition is, but, we only call for ten minutes at one site, because, if a spotted owl is going to call, it’s certainly going to call within ten minutes. If it doesn’t call within ten minutes, you might call for an hour, and it might ultimately respond to you, but most of them, if they’re going to respond, will do so within ten minutes. So that’s why we limit it to ten minutes – our calling – just to be more efficient. And then once we hear them, we mark them, and then we go back the next day to try to locate them, because they will call in the daytime as well as at night, which owls do not do, they do not call readily in the daytime – all owls will call at night, but many of them will not call during the daytime. Spotted owls will.

ES:

RG: What we’re doing, is essentially we’re trying to elicit a territorial response from them. So, spotted owls are territorial, meaning they defend a particular area around their nest. They have a large home range, but there’s some area that’s smaller around their nest that they physically defend, or vocally defend from other Spotted owls. And so, if you hoot, you’re basically saying I’m an intruder, I’m in here. And then that Spotted owl says, hey bub, you better get out of here. And so you do this by going back and forth, announcing their presence. When they get upset, they change their calls, and the have what we call a series of calls, which is an extended series of hoots, then you know that they’re mad at that point. So that’s what we’re trying to do. We’re trying to stimulate them, or trying to fool them into thinking that there’s an intruder in their territory. And then we can take advantage of that by locating their position, and then finding them.

ES:

RG: Not that we’re aware of. We think that if there is excessive calling of owls, particularly if a female is on the nest, this could be a negative thing for the owls. Because if the male gets agitated, the female actually might leave the nest too to help that male defend, because the females will help defend the territory as well. She will leave the nest and the eggs and or the babies unprotected, and they might be exposed to predation or to bad weather. But we are very careful about when we do this, how often we do this, and we limit the duration of our calling such that we don’t believe that we have any negative effects on the owl from our scientific work. And the fact that our estimates of survival are so high, easily around 90% or greater, that we don’t think that there’s any reason to believe that we’re affecting the owls at all. But we recognize that that could be a problem if people did it inadvertently or excessively.

ES:

RG: Well, that gets back to the habitat selection. The habitat of the Spotted owl is primarily conifer forests. But these conifer forests very greatly, from the Northern part of the range, to the southern part of their range. For example, in Oregon or Washington, they live in Douglas fir forest, western hemlock forests, and almost pure conifer forests. As you move further south into Northwestern California and Southern Oregon, the habitat still maintains itself as Douglas fir, but then there’s a species of hardwoods in the under storage, like tan oaks and black oaks, and golden chinquapin, and species of trees that produce mass and food for the prey that Spotted owls eat, such as wood rats. And when you get to the Sierra Nevada, there are forests that are fir forests and white fir forest and under story of smaller conifer trees. And then we begin to see, the Sierra Nevada and further south in their range, where some owls will inhabit oak forests, where there are very few, if any conifer trees. But these oak forests are special in the sense that they’re almost always in deep canyons with a stream there, or water, and they’re very dense, the canopy is very dense, and it’s cooler than you would expect from being in that particular area. And then as you go further, to the southwest, you find them again in oak forests and pine oak forests as well as mixed-coniferous forests, but you also find a unique situation where in some areas like Zion National Park in Utah, they live in these canyon lands which have very few trees in them. But the canyon lands themselves might be only 50 feet across and 1000 feet deep, or hundreds of feet deep. The structure of the canyon itself provides similar kinds of environmental conditions that a complex structured forest would have. For example, what we think in terms of habitat selection for Spotted owls is that it’s the complexity or the structure of the forest that’s the key issue for the owl inhabiting that site. That is, there are multi-layers in the canopy that provide a lot of shading, provides a lot of perches, and when you get that high canopy enclosure, it reduces the amount of under story or shrubs in the forest, so that the under part of the forest is easy for an owl to fly through. And it’s cool – these owls get heat stress fairly easily, so the forest, with it’s heavy cover and complexity, maintains its cool environment. Well, these canyons, even though they don’t have any trees, are providing the same kinds of environment, structurally, because the narrow canyon walls with water in the bottom provides a cool and humid environment. The ledges act just as limbs do in the forest. They provide perching sites and roosting sites for the owls, as well as nest sites. So, one of the reasons why owls are often found in older forests is because there are more nest sites there, because a tree might break off at the top and it rots, and provides a flat structure for owl to lay its eggs on. Because they don’t build their nest, the depend on a preexisting structure built by a squirrel, a raven, or a hawk, or an accumulation of debris, or a cavity in the tree, for their nest site. So all of these sites are usually more prevalent in older forests, and likewise ledges in these canyons are available for nests for these owls. And, again, there’s a tremendous complexity of the environments that this owl inhabits across its range. But they all ultimately provide all of the essential things for the owl. They provide places for nest sites, they provide places for roosting, they provide food and shelter and habitat for their prey, and they tend to be cool and moist relative to the surrounding area.

ES:

RG: Well, so far as we know, they’ve inhabited these habitats for thousands of years. Genetic studies suggest that this is the case. There’s some differentiation that’s occurred between owls that are in these canyon lands in Utah and northern Arizona relative to the birds that are found not too far to the south. So there is some genetic differentiation that suggests that they’ve been there for probably thousands of years. But, I should say that even though I’ve talked about these canyon lands at some length, they really are not that important in terms of the total numbers of owls that there are. So there are owls there, and they appear to be persisting, and much of the habitat is protected in the National Parks. But, they aren’t abundant there, relative to how they are in forested habitats. My primary point in bringing them into this conversation is that if all of these requirements are met by the owl, the cool forests, the complex structure, the presence of prey and the presence of nest sites, then these owls inhabit these sites. So they have to have all of these, and the canyons just happen to provide these. But there’s just not that much of these canyons, and the canyons have to be of a certain kind of physical character before these owls will actually use them too – because if they’re too wide, or it’s too hot, they won’t use them.

ES:

RG: It’s sort of an anomaly; I’d say 98-99% of the owls are found in a forested environment.

ES:

RG: I think I’ll break it down by subspecies. The Northern spotted owl was their subspecies, of course that raised the initial concern about the status of the population because there was some thought that because of rates of logging, and their use of these old forests, that they would go extinct if all of these old forests were cut. So, in 1990 there was a decision to list the Northern spotted owl as a threatened species, based primarily on the loss of habitat, mainly these old forest, subsequent to that time, and actually starting before that, in 1985, there were long-term population studies that were established, one of which, my colleague Alan Franklin and I started down in Northwestern California, and there were others in Washington and Oregon. Over time, more studies have been added by other people in the Northern spotted owl range. And, what we’ve seen in the most recent analysis this year, 2004, is that some of these populations are still declining, and apparently some of them quite dramatically. There’s a big report that is available on these analysis from the Fish and Wildlife Services. So, one thing that’s happened, subsequent to the listing, is that under President Clinton’s leadership, there was a Northwest Forest Plan that was developed as a comprehensive strategy to conserve a large amount of the remaining old forests for the purposes of, not only protecting the owl, but all of the other species of fish and the biodiversity represented by these forests. And that was approved and put into place in the mid 1990s. Having said that, the Northern spotted owl is still declining in some areas of their range, particularly in Washington. And, in British Columbia – the range of the Spotted owl goes into southwestern British Columbia – probably is facing imminent extinction, because there are so few owls left. Anyway, getting back to the status of the owl, despite this very important piece of conservation, the Northwest Forest Plan, the owl in some areas is still not doing well. Subsequent to the listing decision, new threats appear to be emerging. We are uncertain about the extant of this threat and how they might affect the owl in the future, but we’re concerned about them as scientists. And, one of them is the Barred owl, which is native throughout much of Eastern North America and Eastern Mexico. It has invaded the range of the Northern spotted owl – whether that’s natural or mediated by human beings is unclear at this time, and we’ll probably never know. Nevertheless, it’s come in to the range of the Northern spotted owl. It’s somewhat similar in appearance to the Northern spotted owl but it’s bigger, perhaps more aggressive than the Northern spotted owl, and some scientists believe that it’s displacing the Northern spotted owl from their territories. We’re concerned about the possibility that West Nile Virus will affect the Northern Spotted owl – it hasn’t, so far that we know about. But that’s a concern. And so we can say that the status of the Northern spotted owl may have improved in some parts of the range, but not in all parts of the range.

There are many studies of Northern spotted owl population dynamics, such that there’s a very large proportion of the range of this subspecies that is in a study area, trying to investigate their status. The sum total of these study areas, and the number of birds that have been individually banded so that we can identify individuals, probably represents the largest single study of population dynamics of an endangered species ever conducted in the world. So it’s a monumental effort. And despite this great amount of effort, we still have uncertainty about some of the populations and what their status is. And so that tells you something about the complexity about answering the question – is the population stable or isn’t it. It seems like a straightforward question, but it’s quite a difficult one in terms of finding owls, capturing them, and banding them, resighting them, and then estimating survival rates and fecundity rates based on these data. And so even though it’s a monumental effort, and a testament to the willingness of scientists to cooperate – because we all pool this data from all of the study areas together to do one giant analysis, called a meta-analysis – we still have uncertainties about the status of the owl, and moreover, about why these populations are doing what they’re doing, what’s causing their decline. We know that there are some obvious ones in the past, habitat loss, but what’s happening today? Why are the populations still going down in some areas in Washington? It could a combination of things, it could be a combination of weather, the Barred owl, past habitat loss, but we’re just uncertain about what it might be.

Now, having said that, the next subspecies that’s been studied in some detail is the California spotted owl, which occurs from Northeastern California at the northern end of the Sierra Nevada and southern end of the Cascade range, south to Baja in Mexico. And this subspecies is different in a couple of ways from the Northern spotted owl. One is, of course, it’s genetically distinct. So we know that this California spotted owl has diverged to some degree from the Northern spotted owl, so that they’re actually a unique taxonomic entity, a unique form. But they also occur, not only as a big, contiguous population in the Sierra Nevada, but also as smaller, semi-isolated populations in central California, and throughout southern California. So, anybody that flies over southern California and looks at these mountain ranges, starting at around Palm Springs that surrounds the L.A. basin, almost all of those mountain ranges has a little population of Spotted owls on it. And, presumably, historically, they’ve moved between these areas through riparian zones or even simply directly. But they’re not very large populations, and they’re relatively isolated. Well, there have been five big population studies of the California spotted owl that have been ongoing for up to 18-19 years. That’s the longest-term population study of the California spotted owl population. We started in 1986. What we’ve seen, in these populations that have been studied in southern California in the San Bernardino Mountains by our research crew, and one of my former associates and graduate student Bill Hay, this population has probably declined by 50% since we started studying it in 1987. But that study has been curtailed as a result of lack of funding, and so at the last counts that we had, the populations had declined by almost 50% over the 13-14 years that we’ve studied this population. The populations in the Sierra Nevada are more ambiguous about what trend they have shown. But it appears that populations are declining slightly over time, although there’s some uncertainly about whether that rate of decline is different than a stable population. In other words, even though the estimates, the actual point estimates of the actual rate of decline are less than what you’d expect from a stable population, there might be the confidence around that estimate might be large enough to where you can’t really distinguish that from a stable population. However, one of these populations under study, which is quite interesting and provides a big contrast to the other three in the Sierra Nevada, is a study that’s occurring in Sequoia Kings Canyon National Park. And that study area, its management is really quite different. Everything is protected, the habitat is protected, and there isn’t any logging, there isn’t much habitat destruction that’s caused by humans relative to the other three in the Sierra Nevada, which are subject to a combination of logging and development that occurs as a course of normal progress. And, that population that’s entirely protected seems to be doing better than the three that are in areas that are considered to be available for multiple uses. And I should say that the Forest Service, at the present time, is reviewing how they’re managing the owl, and it’s unclear what the final resolution of their management strategy will be, and that could be important for the future of the owl. And I will say that prior to their recent strategic shift in management strategies, there was an internal plan that was instituted in 1992 that provided internal protection for the California spotted owl throughout its range, by protecting core areas and limiting logging to certain kinds of logging in its preferred habitat.

Now, moving on then, to the third subspecies, the Mexican spotted owl, just like the southern part of the California spotted owl distribution, most of the Mexican spotted owl populations are found in semi-isolated mountain ranges, scattered from southern Utah to southwestern Colorado, all the way down almost to Mexico City, the state of Michoacan. And in each of these mountain ranges there is a population of Spotted owls, and they range in size from very small, 5-10 individuals in the smallest ones, to some fairly large ones on the order of hundreds of individuals in other populations. And, we know the least about this subspecies because there have only been two population studies that have occurred in the Southwest that had any length of time associated with them. And those are the two that my students and I have started conducting in the early 1990s, and they lasted about 10 years, and then they also were curtailed because of lack of funding. But it appears over the period of time that we studied these two populations that there was a general decline in both, and one appeared to start recovering. So we’re not clear about whether or not the decline of the owls, and then the potential recovery of one and not the other is due to the effects of this long-term drought that’s occurring in the Southwest, or whether or not one’s population’s habitat was worse than the other, and therefore this population is declining as a result of poor habitat quality. And so, the investment in effort in studying Spotted owl population dynamics has not been nearly as extensive for the Mexican spotted owl as it has been for the other two subspecies. I should say that there is another study that’s occurring in the Sacramento Mountains in New Mexico by one of my former graduate students as well, and his study is primarily about the relationship between the Spotted owl and its prey. He’s found that these owls’ reproduction is highly affected, as you might expect, by the fluctuations in the prey. Whereas we think that the Spotted owl is a specialist on medium size small mammals – that is a wood rat is something that we would consider as a medium size mammal. They weigh about 180 grams and a small male Spotted owl is only about 500 grams, so a male spotted owl killing a big wood rat is taking a pretty substantial sized animal relative to its body size. And that seems to be, if one looks at the diet of Spotted owls across its range, wood rats and flying squirrels, which are these medium size mammals, appear to make up the majority of the biomass, or the majority of the prey by weight, that the owl eats. Now, having said that, they eat a variety of other things, from insects to mice, and the study in the Sacramento mountains by Pat Ward, has shown that when these mice are super abundant, than the owls may breed in response to that. So even though they seem to be a specialist on these medium sized small mammals, and the dynamics of those medium sized small mammals appears to be able to maintain these owls through good and bad times, sometimes when these really small mammals that they eat as well, like mice become really abundant, the owls focus on those and will exploit them. So I think that covers our breadth of knowledge – that we know most about the Northern spotted owl, we know a great deal about the California spotted owl, but less than the Northern, and the Mexican spotted owl we know the least of all three subspecies, in terms of their population dynamics.

ES:

RG: Critical habitat is an extremely complex issue for several reasons, and these reasons are all interrelated. First of all, critical habitat is a term that’s designated in the Endangered Species Act. It’s not something that somebody has defined scientifically, and therefore it’s somewhat open to interpretation what critical habitat for an endangered species is. In general, one can think about it in terms of the Endangered Species Act as that habitat, if it were lost, it would lead to a degrading status of the species in question. And that’s sort of a broad way to think about it, and if one does think about it that way, then virtually a large amount of the environment of the owl can be considered critical habitat. So therefore you have people who have interest in protecting the environment, and people who have economic interests. There are people, for example, who would like to log trees, who have opposing views of what the critical habitat should be. For example, taken in the broad scheme of things, people interested in maintaining as much of the natural environment as they can, let’s say that any loss of habitat known to be suitable for a Spotted owl would be a degrading of their status. Whereas, people who are interested in using trees or harvesting trees for human use might say that, we really only ought to protect that habitat, or enough habitat to allow the species to persist. And we can see that those are really different things. And so, as a scientist, we’re often asked the question – how much habitat is enough? And the answer to the question is, we don’t know, because it’s extremely complicated because habitat quality varies by area, by different forest types, by individual sites. So, some sights are clearly better than others, because we know that owls reproduce more, have higher survival rates in one habitat versus another. But, at this point in time we’re not at the stage of knowledge that we can identify the best sites, and how much of those best sites are necessary to insure that the population doesn’t go extinct. And so, that really puts scientists in a difficult position, because these are two quite different viewpoints of what critical habitat could be. And our job is to try to move forward in our science, and try to understand that, but that really takes a lot of effort, and I think that there’s a great deal of frustration on both sides of the issue, that scientists haven’t been able to answer that question. But it takes a long time to understand how individuals do in a particular habitat, and once those individuals are gone, do the birds that colonize those areas; do they have the same kind of success? And if they do, then you know that that’s really good habitat, and if they don’t, then well maybe it was the quality of the individual owl that made the difference for that habitat, and not the habitat per se. And so, these questions are quite complex. The question of critical habitat is one of the most contentious issues associated with the owl and the Endangered Species Act.

ES:

RG: You know, the first thing that came to my mind is the pun, fire is another hot-button issue. But, fire, is again, one of these very complicated, controversial issues. On one hand, fire is a natural part of most of the forest inhabited by the owl. On the other hand, because of fire suppression, there has been a great deal of accumulation of fuel, such as dead limbs and brush in the forest, including most Spotted owl forests, that the fires that ignite now are catastrophic. And that is, they actually destroy the forest rather than rejuvenating it. And this is become a concern for people interested not only in conservation of owls, but also in conservation of forests. Having said that, it’s also potentially a very contentious issue, because people have used the threat of fire as a way to do things that they probably shouldn’t, in terms of logging of forests. We know that spotted owls evolved with fires, and so fires by themselves are not a threat to Spotted owls unless it actually destroys a forest. So, if a fire burns though a forest occupied by a population of Spotted owls, and it’s of low or moderate intensity, it’s probably not going to have much of an effect on them long term. It might affect the reproduction in that year, but it’s not going to affect their survival or reproduction in future years, because they’ve evolved and they can escape it, and they can re-nest in the same trees. It’s when fires become so intense that they actually destroy the forest itself, that it affects the owl. And the reason why I say that this is such a contentious issue is because there has been legislation that’s been approved under the Healthy Forest Initiative, which allows for thinning of forests, presumably to help protect the forests against fires. And, in fact, if applied appropriately, this can be a very beneficial thing. That is, if thinning of forests occurs from below, in other words taking the smaller trees and then doing controlled burns to allow removal of accumulated debris on the forest floor, this can really mitigate the impact of fire, both on Spotted owls, and on people and communities and so forth. But, if logging that occur under the Healthy Forests Initiative really takes the larger trees, because they’re more valuable, and leaves the smaller ones, then we haven’t accomplished anything. Therefore, the issue of fire is very contentious. People are concerned that this initiative will be inappropriately applied and it will be detrimental to the owl. One of the things that scientists have been urging is that all of the actions taken under the Healthy Forests Initiative, or anything else that’s done within the realm of management for Spotted owls be done within what we call an adaptive management context – where there is monitoring, of the results of that action, such that we can learn from our management, and then make adjustments to the type of management, whether it’s negative or positive, to continue that management action. So, again, fire is a big issue. It could be very important for the Spotted owl over its entire range if there are large, catastrophic fires that remove large amounts of owl habitat. But, if logging to reduce fire risk is not done appropriately, it could be just as damaging as the fires themselves. So I think that scientists are hopeful that land management agencies that are in charge of this will engage in a program of adaptive management, to actually monitor the results of their actions to reduce wildfire.

ES:

RG: We’ve proposed studies to do just this, in the Sierra Nevada’s. And, we’re waiting now to see whether the Forest Service is going to agree to conduct these studies in the future. The Forest Service has been very good about funding the research on the Spotted owls over the past two decades, and we’re hopeful that they will continue that level of commitment in the future, especially to do these kinds of experimental studies.

ES:

RG: Well, there’s no question that the owl has to have habitat, and good habitat, to be successful. And, so, everything starts from the habitat. If there’s no habitat, the owls aren’t going to be there or they aren’t going to do well. So, having said that, that’s the primary factor affecting the owl. We’ve made some very good progress in the Northwest, in the Northern spotted owl range, at protecting habitat. And, there’s been progress in the Southwest – it’s not clear what’s going to happen in the range of the California spotted owl, but I’m hopeful that that will a good management plan for them. Having said that, there are other things that are superimposed on the owl’s dynamics that affect the owl’s dynamics, that must be considered as very important. One is, they have a strong response to weather. So, we know that in years that are very wet and cold in the spring, in the Northern spotted owl for example – the owls don’t do very well, reproductively. We think that it’s probably a combination of not being able to find food, or having high-energy costs because it’s cold and wet, and this might affect the survival of the young, or even the adults. So that weather can have a big effect on the birds. There’s the invasion of the barred owls, that introduces a competitor, and that may have a serious effect on the owl. And so, we’re worried about West Nile Virus as a potential future threat, it’s not known to affect them now but it might in the future. So, you have to have habitat for a basis for this bird to exist, but there are other things that also affect its dynamics, like weather and the presence of competitors.

ES:

RG: One of the things that’s a little bit controversial with the barred owl is, how did it get from the East coast to the West coast. We know that it somehow came, either through Canada, or through the northern states like Montana and Idaho and then into Washington, but it’s not clear which one of those it was. Some people have suggested that this movement was facilitated by either the development of the Great Plains and the intrusion of fire there, whereas before you had just uninterrupted stretches of grassland, because people built towns, they stopped fire. There were riparian zones, which are forests that go along rivers, these all began to develop and provided natural corridors, or stepping-stone habitats across the Great Plains to allow the barred owl to move into Northern Canada, and then across into the Pacific Northwest. It’s also possible that they could have just done this naturally as a result of gradual changing climatic conditions, and maybe perhaps warming, that they were able to move over. Irrespective of that, we’ll never be able to know what facilitated that movement across, into the range of the Northern spotted owl.

ES:

RG: Again, here it’s complicated. What’s happening is that you now have two species that are in the same genus – they’re reasonable closely related. Barred owls and Spotted owls are not as closely related as you might think just by looking at them. If you look at them you might think, gees, these things are closely related, but genetically they’re not that closely related. Having said that, you have two species that are exploiting a similar kind of niche, as it were. They both eat small mammals, medium sized small mammals, and as I mentioned earlier, the Spotted owl is more of a specialist on medium sized small mammals, whereas the Barred owl has a much broader diet. So it eats frogs, and it eats lots of mice, it eats pocket gophers, and the same things that Spotted owls eat. It also has a wider tolerance of habitat. It uses forests that have been logged before, forests that are found along rivers, the riparian areas, yet it’s found in old forests, just like Spotted owls. So you have one species that’s a specialist, and the other one that’s a generalist. And so that suggests that there’s going to be competition for habitat and for food. And then when we bring in the size difference, Barred owls are bigger than Spotted owls, and therefore they ought to have a physical advantage to them in any kind of a physical interaction. On top of that, some scientists feel that Barred owls are behaviorally more dominant, or more aggressive, than Spotted owls. That hasn’t been demonstrated conclusively, but there is some suggestion that they may be more aggressive. So when you add all of those things up, a species that is larger, potentially more aggressive, eats the same food and other foods, uses the same habitat and other habitats, you wind up with a potentially superior competitor. If that happens, two species in the same environments like that are going to compete, with potential outcome that the Barred owl is going to win in many of these situations. And that leaves us with, what’s going to happen under these scenarios? There are a whole lot of different outcomes that can happen, all the way from a complete displacement of the Barred owl by the Spotted owl, to situations where the Barred owl might be the superior competitor in some areas and not in other areas. If Spotted owls in the Northern part of their range are focusing only on one or two prey species, and then they have the Barred owl to compete with, the Barred owl uses those species plus other ones, the Barred owls would clearly be at an advantage. Well, in the southern part of the range, the Spotted owls may be superior because they’re specialists that are able to out compete the Barred owls in certain kinds of situations. So there are all sorts of potential outcomes, and we simply don’t know what those outcomes will be at this point in time. People in my group, as well as Alan Franklin, we’ve been cautioning people that we just don’t know what the result of this interaction will be. We need to be concerned about it, and we need to watch this and conduct experiments and studies to find out what the nature of those interactions are. But we simply don’t know what the ultimate fate of Spotted owl is going to be in the face of the invasion by the barred owl. It can be really bad, it could be partially bad, we really don’t know.

ES:

RG: We discussed earlier about the conservation problems and the issues associated with that, and we kind of lost sight of the fact that this owl is just a magnificent animal just on its own. It’s got a wonderful life history, it’s complicated, and it’s interesting. This animal has evolved very successfully within its habitat. And it’s now facing situations that it hasn’t faced in its evolutionary history, logging, the invasion of Barred owls, and so forth. And so I think we have a tendency to focus on the politics and the controversy, the politics, and forget that this is truly an interesting and magnificent bird, that has a great deal of interesting life history and things that we can learn about it.

After studying this bird for almost a quarter century, it’s incredible just how complicated it is to understand whether its population is stable or declining. I mean, that’s really difficult. We’ve devoted a huge amount of time to that. And when you think about just how difficult it is to do that, to answer that question, just think about how intractable some kinds of conservation problems are. Some people think that they ought to be able to be easily solved, but they can’t be solved easily. They’re just complicated, and there’s no way you can get around that. And likewise, when you have a huge amount of money at stake, like the value of these forests, and the lumber that’s represented in those trees, it just becomes that much more intractable, because of the interest and the money at stake in these issues.

> Captured and banded several thousand owls

One misconception that seems to be gaining momentum seems to be that the owl is not threatened or in trouble in any way. And in fact, there is good evidence, good scientific evidence, that it is. On the other hand, there is a widespread misconception that Spotted owls only exist in old, ancient forests. Whereas, ancient forest is habitat for spotted owls, they can often be found in other kinds of forests. But you can’t make the leap, that because they’re found in other kinds of forests, that simply logging forests, owls will adapt to that. And that’s another misconception. People think that, why can’t the owl adapt? They have wings, why can’t they fly someplace else? And that’s a legitimate question to ask. And the reason why they can’t adapt, is because they’ve evolved in an environment under a certain set of environmental parameters, and that’s what they’re programmed to live in. And if you change it, they can’t easily adapt to that. And that’s the way it is with all animals. One of the things, as humans, we often forget is that, as a species, humans are one of the most adaptable species on the planet. We can create our own environments; we go into the Arctic and live. But other animals have to live with what they have in front of them. And if they’ve evolved to live in a certain type of forest, a certain type of weather regime, than that’s what they’re going to do best in, and they’re going to do poorly elsewhere. Likewise, if you move their habitat, and they move to another place – and they will, they’re not necessarily going to just sit on a stump and die. They will in fact use their wings and fly, but most other habitats are occupied by owls. So, it’s not a simple matter of moving and finding another place easily if you’re displaced by a natural event or an unnatural event. So I think that the public needs to remember that both sides of this controversy you have to be careful about what people are saying, and I think rely on what scientific information is available.