PubTalk 11/2018 - California Birds
Title: The Least Bell's Vireo - A flagship species for riparian ecosystem conservation
The Least Bell's Vireo (Vireo bellii pusillus) is a songbird that is endangered in California:
- What type of research is the USGS doing to help understand the threats these and other birds face?
- How has our research during the last 30 years given us optimism of what is in store for their survival and their future?
- Why is it important for us to continue the conservation and management of the Least Bell's Vireo?
Image Dimensions: 1272 x 720
Location Taken: Menlo Park, CA, US
This video is a one-hour presentation of the USGS Evening Public Lecture Series titled, The Least Bell’s Vireo, a Flagship Species for Riparian Ecosystem Conservation. The presentation is being hosted in the USGS Menlo Park facility. The host welcomes the audience and introduces the speaker, Barbara Kus, who is a USGS research ecologist. As Barbara is giving her presentation, she is continually pointing to and referring to slides presented on the screen. The slides are a mixture of charts, graphs, and photos. At the end of the presentation, there is a question-and-answer session with members of the audience.
- … Geological Survey. I’m Diane Garcia, and I’m with our Science Information Services, and I’m really delighted that you all made this November lecture on this rainy night. Before I go ahead and introduce this evening’s speaker, I want to remind you, we will not be having a December lecture. It’s a busy time of year, and as you can imagine, it’s often difficult to book a speaker for that. But the good news is, we’re going to be back in January. Kristin Byrd, with our Pacific Region, is going to be giving a talk about remote sensing for ecological forecasting on January 24, 2019. And so I’m hoping you all save that date, and I’m really looking forward to seeing you all in the new year. There’s fliers in the back as usual, so you might want to pick one up, so – put it on your refrigerator or something so you can remember to come back. But what we’re really here for, the main attraction tonight [laughs] is a lecture, The Least Bell’s Vireo, a Flagship Species for Riparian Ecosystem Conservation. And it’s going to be given by Dr. Barbara Kus. Barbara is a research ecologist with the USGS Western Ecological Research Center in San Diego, California, and a research professor of biology at San Diego State University, where she supervises graduate research in avian ecology and behavior. She received her Ph.D. in ecology from the University of California-Davis. Barbara’s primary research interests include the ecology and demography of threatened and endangered species in riparian and coastal sage scrub habitats; the response of endangered species to management to reduce threats such as cowbird parasitism and wildfire; the effectiveness of habitat creation and restoration as a tool for conserving riparian bird communities; the landscape-level analysis of the impact of urbanization on regional bird populations. She’s been conducting research on least Bell’s vireos in southern California and Baja, California, for over 30 years and is author of the Vireo Recovery Plan. Dr. Kus works extensively with wildlife and regulatory agencies and is a member of several advisory boards and endangered species recovery teams. So the USGS monthly public lecture series is very pleased to bring you a program this evening about those wonderful songbirds, the least Bell’s vireos. And I ask that you please hold your questions until the end of the lecture. Let’s really give a big, warm welcome to Barbara. [Applause]
- Thank you very much, Diane. I’m really happy to be here tonight. And given Diane’s remarks, you know I mean, I’m really happy to be here. [laughter] It was a interesting journey getting here on what seemed like such a straightforward short flight this morning. And I appreciate the invitation to come and speak with you tonight. And I also want to thank you for braving the weather and coming out. And, for those of you streaming in in your PJs and slippers sitting by the fire, welcome. I’m glad to have you as well. So 33 years ago, I arrived in San Diego as a newly minted Ph.D. And I was invited to lead a research program that would serve as the basis for a comprehensive species management plan for the least Bell’s vireo. And I had never heard of the least Bell’s vireo, even though I was a birder and interested in avian ecology. And I hadn’t heard of them even given that they should have occurred near where I went to school at UC-Davis. And, in fact, they should have occurred near where I grew up in northeastern Los Angeles. Because that was part of their historic range. So I did what anyone would have done and said, sure, I can do that. And I thought that I would work on this project for a couple of years, and then I’d move on to something else. And so here I am, 33 years later, still working with least Bell’s vireo. So I have a lot to talk about. [laughter] I’m not going to talk about it all tonight, but what I would like to do tonight is just give you some of the highlights of the path towards recovery for least Bell’s vireo, past, present, and future. So, to start with, I want to provide you with some context. Now, California, as we know, is a state of just unparalleled geographic and topographic diversity. And consequently, it is biologically very diverse. In fact, it is such a special place that it is recognized as a global biodiversity hotspot – not just a regional, not a national, but a global biodiversity hotspot. We have a very rich flora and fauna here. Many, many endemic species that occurred nowhere else in the world. So we have this very precious biological heritage in our state. And, as you know, millions of people love California. And, as a result, California also has the dubious distinction of having more threatened and endangered species than any other state in the continental U.S. We outrank Florida, which is the state with the next-most number of species. We have twice as many listed species as Florida does, at somewhere approaching 300 listed plants and animals. And so, this sets the stage for significant human impacts on natural resources and natural systems. Much of the biodiversity in California and in the southwest in general is associated with riparian habitat. This is the shrubby, forested habitat that occurs along streams and rivers that grows along the shores of bodies of water. And these are tropical forests of the temperate regions. And we’ve all heard about how important tropical forests are. These are highly productive ecosystems. They provide critical components to sustain human life. And also support a disproportionately high fraction of wildlife relative to their coverage on the landscape. Riparian habitat might make up 1% or less of the land cover, but supports more plants and animals than any other terrestrial ecosystem. So it’s very, very important. These kinds of settings provide water, access to water, shade, nest sites, den sites, food, cover during inclement weather – all sorts of things that animals need during at least part of their annual cycles. And they’re essential to maintaining regional biodiversity. In particular, in arid regions or mountainous regions, such as these in southern California, where the habitat occurs as a narrow band at the base of otherwise semi-arid uplands, and much of the diversity in this area as a whole could not survive were it not for access to the resources in these riparian corridors. So, as I mentioned, southern California and California in general supports a very large human population, most of which is concentrated near water. In southern California, where I work, the area encompasses only about 1-1/2% of the land in the United States, but we support 8% of the human population. So there are a lot of people trying to live in these areas. And this has created impacts on ecosystems, not just by the presence of the urban footprint itself – the houses and the shops and the commercial buildings and so forth that we – that are part of our existence, but through a number of activities that affect riparian habitat, such as – things such as in-stream sand and gravel mining; agriculture which removes vegetation from flood plains and shaves the habitat down to these narrow bands along the edges of fields; recreational uses like golf courses, which are green, but they don’t really support the structure of the vegetation that you were just looking at; flood control projects that involve concreting in the channel bottom and the margins along the side. So all of these things have taken their toll and contributed to a loss of habitat. And then, of the habitat that remains, much of it is degraded by invasive exotic species, including giant reed – this is that tall bamboo that you’re probably familiar with. It’s used in landscaping. It’s also very prevalent in our riparian areas now. It was originally brought in to stabilize banks along creeks. Well, it does that. [chuckles] And it pretty much has taken over areas that it has invaded. And then saltcedar is another invasive species that is displacing the native willows and cottonwoods and sycamores typical of native riparian habitat. This is an aerial view of Marine Corps Base Camp Pendleton, where we do a lot of our work. This is the Santa Margarita River, our last free-flowing river in southern California. All of this light-colored green vegetation is giant reed. And then there are just a few little dark green heads of willow trees poking up. So this vegetation is essentially choking out the native vegetation. And the giant reed does not have value to wildlife. Birds tend not to forage or find nest sites or find it as a replacement for native vegetation. So, as a result of these kinds of impacts, over 95% of California’s riparian habitat that was present at the time of the Gold Rush has been lost. It’s probably even more than that today. And it’s been inevitable, with habitat losses like this, that many birds species have declined, especially in the last 50 to 75 years. There were tremendous declines between the 1950s, for example, and the ensuing decades. And so these species include things like the black-headed grosbeak, the Wilson’s warbler, Swainson’s thrush, the yellow warbler, yellow-breasted chat. Not all endangered birds are yellow, but many of them have yellow in their names. [laughter] Southwestern willow flycatcher and least Bell’s vireo. So – and there are more that I could put up here, but these cover a range of federally threatened and endangered species, but they also include some of the other species that are on other kinds of lists of species of conservation concern, like the Audubon Watch List or some of these other lists. Now, I want to point out that, even though tonight I’ll be focusing on least Bell’s vireo, I’m really talking about all of these. And vireos share threats with these other species. And, in that sense, the decline of the vireo has been emblematic of what is going on with so many other individuals in the riparian bird community. And, in that sense, it truly is a flagship for riparian ecosystem conservation. So we’re certainly not focused on doing single-species management, but I don’t have time to talk to you about all of these species, and, as I said, they do share so much in terms of the threats that face them that the vireo is a good representative for them. So least Bell’s vireo is a migratory species. It spends the winter in Baja, as many of us wish we could, and some of us get to do a little bit. And while it’s in California, it’s on the breeding grounds. So it’s here between March and September or so of each year. It’s dependent on riparian habitat for breeding. It cannot breed anywhere else. Oops. Something else was supposed to pop up there. Oh, here we go. Historically, vireos occurred in riparian lowlands from southern California all the way up through the Central Valley to Redding. They got into the desert. And they also occurred in northern Baja, although this part of the range is less well-known. And, as a result of this widespread, massive habitat loss, the range was restricted, largely to southern California and northern Baja. And by the time the species was listed, it numbered just 300 territories. And most of those were in my new backyard here in San Diego County. So we have a species that went from being one of the most common songbirds in riparian habitats throughout our entire state to one that was critically endangered. The vireo is an open-cup nester. The male and the female work together to construct these grass nests that are hung from a fork in a willow or similar-structured shrub. Here is the nest, by the way. Vireos rely on concealment to protect their nests from predators. This nest is about a meter from the ground. So they have very low nests and definitely need to rely on concealment to hide them. Typically, females will lay three to four eggs. They hatch within a couple of weeks. The young are naked and hungry. [laughs] They are featherless for the first few days of their lives. After almost another couple of weeks, they’re feathered and ready to leave the nest. And, once they fledge, they are dependent on their parents for feeding for at least a couple of weeks before they’re ready to face the world on their own. Now, in addition to habitat loss, one of the threats that vireos and many other riparian species face is that of brown-headed cowbird parasitism. The cowbird is what’s called a brood parasite. And what that means is that, it lays its egg in the nest of another species, called a host species, and then takes off to leave the host parents to raise it. This is a fascinating ecological life history, but it’s creating a lot of problems, especially for western birds. Cowbirds are native to the eastern United States, where they would follow bison herds and feed on the insects that were stirred up as the herd moved through the grasslands. And the thinking is that they did not have time to build nests and raise young and stay in one place long enough to do that. They had to keep up with the herd. And so this is a lifestyle that evolved, that allowed them to pop eggs into the nests and then carry on with the rest of the herd. And so species – bird species – host species in the east have had time to evolve defenses in response to cowbird parasitism. For example, many of them can recognize this cowbird egg and eject it from their nest. Or they might abandon the whole nest and start over rather than go – put in all the time to eventually raise a cowbird chick. Many of you have probably seen photos of little tiny warblers or vireos feeding big cowbird chicks that are many times larger than their parent. In contrast, cowbirds have only been in California for about a hundred years. They followed livestock grazing west and are a very recent arrival in our bird community. And species that breed here have not had time to evolve defenses. And parasitism usually takes a very strong toll. The host parents are not able to fledge their own young. The fledge a big cowbird chick. And sometimes the cowbird female, when she’s laying her egg in a vireo nest, for example, will remove one of the vireo eggs, which automatically reduces the potential for vireos to fledge any of their own young. This cowbird egg will likely hatch sooner. The chick will be bigger. It will grow faster. And after a few days, it can look like this. It’s out-competing any vireo chicks that might have hatched, and they die of starvation. And this is what we’re left with. So cowbird parasitism really can take a toll on productivity of a species like Bell’s vireo, and it doesn’t take many years of reproductive failure for a species to really seriously decline. So when the species was listed in the mid-1980s, it made sense that the initial recovery actions were to reduce cowbird parasitism and to increase the availability of suitable habitat for vireos to recolonize. And this was being pursued by protecting what habitat remains, by habitat creation – growing habitat where none currently exists, and then by restoring habitat. And by this I mean removing invasive plants like the giant reed and the saltcedar from riparian woodlands. And this is where USGS steps into the picture. We play a very large role in conducting the research that determines and evaluates ways to do these things and evaluates if they’re working. And we have a very strong emphasis on endangered species recovery within USGS. So how do we do that? What do we do? I was recently asked to provide a bio sketch for the web page of the American Ornithological Society, which I’m involved with. And one of the questions that they wanted was, badly explain your job in, you know, 40 characters or whatever is tweetable. I don’t know. I don’t tweet, but whatever. And so [chuckles] my response was, I stock endangered birds to figure out what they need to survive. Then I tell anyone who will listen. [laughter] And I think that’s pretty much how my position description reads. But [chuckles] what do we really do? Well, first of all, I certainly don’t do it alone. And every summer, we employ a small army of field biologists to go out and collect data in the following areas. First of all, we’re doing annual surveys at a number of study sites all over southern California. And we do these to determine the distribution and the abundance of vireos. So where are they? Where are they now? And how many of them are there? And this allows us to monitor population trends, always with an eye towards looking for trends towards population increases that are taking them on trajectories toward recovery. So this, by itself, takes a lot of time. It takes people, you know, crawling through the bushes, listening for birds – because we detect them by ear, looking at them, figuring out, you know, what they’re doing and noting their location and so forth. So that’s something that we’re doing every year. Nest monitoring – we search for nests by observing the adults and looking for behaviors that are indicative that they’re nesting in a particular area. And this allows us to monitor nest success. Do the nests survive and fledge young, or did it fail to predators or cowbirds or something else? And we collect the demographic data – for example, the number of eggs they lay, the number of eggs that hatch, the number of young that fledge, and so forth. Was the nest parasitized? In addition, we color band nestlings and adult birds. This allows us to follow individuals throughout their lifetimes. So each bird has a unique combination of color bands. And some birds are banded as nestlings with a single band indicating what drainage they fledged from. And then, if they survive and return, we re-capture them, we give them a full combination. This gives us information on survival of individuals, dispersal, movement, and other things. And then finally, at the end of the season, we perform vegetation sampling, where we have a method that we’ve developed to quantify the horizontal and then the vertical structure of riparian habitat. This photo is really for demonstration purposes only. The work actually takes place inside the habitat where there’s the poison oak and the nettles and the blackberry and the rose, and it takes a real effort to dig down and keep that positive attitude going [chuckles] among the field crew that are measuring vegetation along these fixed transects every year. But this is one of the most important things that we do. Because many of the threats that affect birds don’t affect them directly. They affect them indirectly through an effect on habitat structure. So anything that changes the composition or the structure or the density or what have you of the habitat is then translated into an effect on the bird. And so we need to track the structure of habitat to be able to pick that up. So with these data, then, on population size, nest success, productivity, survival, dispersal, et cetera, these become our response variables – kind of tell us what happened, how do birds respond, in analyses that we design to evaluate the effects of various kinds of threats on birds. And, in particular, the effectiveness of management to reduce those threats. So how well is this management working? So that’s kind of in a nutshell what a wildlife biologist does, what they’re collecting information on, and then what we use to do our analyses. So I want to talk about, just briefly, a couple of the threats that we have been monitoring over the years. And the first one has to do with the effectiveness of cowbird control. Now, in California, cowbird control is conducted using modified Australian crow traps, which is this sort of playhouse-size wire cage. These are deployed in riparian areas where vireos and other birds are breeding. They are provided with water and seed and a small flock of decoy cowbirds – live cowbirds who serve as the social attractant for free-flying cowbirds flying around looking for nests to lay their eggs in. And the cowbirds can drop down through a narrow slot on the roof of this trap to join the fun here. But they can’t fly out because the slot is too narrow for them to – with their wings spread, to fly out. And so these checks would then be checked daily, and the females removed and the males released. So this is an approach that a land manager or resource manager might use to control parasitism on their lands. Or it’s something that a consultant might do for a project where there’s a requirement to do some mitigation for an impact that they’re having on riparian habitat in bird communities. And then second line of defense involves finding nests and monitoring them and then manipulating their contents. And by that, I mean, when we find a nest that has a cowbird egg in it, we remove that cowbird egg so it doesn’t hatch, replace it with a dummy egg – usually, like, a plaster egg, so that the clutch still feels the same to the parents. And that allows the rest of the clutch to go forward, for the nest to stay alive. Now, sometimes these nests will fail later to a predator, but they didn’t fail to parasitism. And we call these rescued nests. So this is another form of management. It’s much more intensive because you have to get out there and find the nests and monitor them and so forth. But sometimes that’s necessary as a second line of defense. And that’s how we collect our data to see how well the first line of defense is working. If the first line is working really well, we don’t find much in the nests in terms of cowbird eggs. So that’s something that we would quantify. So we’ve been monitoring cowbird trapping in this form for several years. And these are some results from three different rivers in southern California – the San Diego River, some rivers at Marine Corps Base Camp Pendleton, and then the San Luis Rey River. And what I’m showing here is the percent of the nests that were parasitized before and after cowbird control was implemented at those sites. And the number in parentheses reflects the number of years that we monitored that site for. So, for example, at the San Diego River, before cowbird control was implemented, 57% of nests were parasitized during a two-year period. And after control was implemented, only 11% of nests were parasitized during a 10-year study. And similarly, 47% before control, down to almost nothing – 4% during 15 years of monitoring after cowbird control. The San Luis Rey River is an example of the – of a place where it’s been harder to reduce parasitism. But still, it was cut in half. And so we’ve seen that these traps are definitely effective in reducing the incidence of parasitism. What we really want to know, though, is what does that do to the number of young that are fledged? And, again, these are the same sites, the same format. And we found, at San Diego River, for example, we went from fewer than one young fledged per pair to almost three young per pair after cowbird control was implemented. This is a very high rate of productivity. Camp Pendleton, we doubled productivity. And even at the San Luis Rey River, where I said it was harder to control parasitism, there still was a tripling of productivity. And what’s important about these values is that they are all above two or very close to two young per pair. And that is the rate that needs to be achieved for a population to be stable. In a sense, the parents are replacing themselves. And anything above 2% – or, two young per pair will translate into population growth. So we really want to see numbers that have a 2 in them, and cowbird control was producing that. But finally, the real currency for our endangered species recovery is how many individuals does that turn into out on the landscape? And I’ll just direct your eyes over here because this was one of the most dramatic responses at Marine Corps Base Camp Pendleton, where, in the early ’80s, there were just a couple dozen vireos on this 125,000- acre military installation. Cowbird control was initiated in the mid-’80s. And the population really just took off and exceeded 1,000 close to 2010. And since then, it’s oscillated. It’s dropped from this peak, but it’s been oscillating around some – somewhat lower number, but probably the actual carrying capacity that can – where a population can be sustained at that level over a long term. So this was evidence that cowbird control was going to be an important tool for vireo recovery and that it was working. What we’ve learned about cowbird control from our work is that it’s effective in reducing parasitism and increasing annual productivity. It’s producing population increases. But it’s effective only as long as suitable habitat exists for these new birds to move into. So, at some point, if there’s no more habitat, you can produce more and more young birds. But if they don’t have anywhere to go, you’re not going to see population growth. But certainly, during the last 30 years, there’s been enough growth and opportunity for this growth to be expanding out of southern California and into the historic range. So I think that we’re – on a state level, we’re a long way from saturating all the available habitat. But, at specific sites – for example, Marine Corps Base Camp Pendleton probably can’t support many more than 800, 900 birds. We shouldn’t expect there to be 5,000 there at any time. All right, now the other main emphasis of the early recovery work was on habitat creation. And the kind of restoration that I’m – or, the kind of habitat creation that I’m talking about here is what we think of as from scratch, where a degraded site, such as this abandoned agricultural field, is graded. Earth-moving equipment is brought in, and the ground is graded to the desired distance of the groundwater table. It’s then planted with mature trees. And often these are brought over from a site that’s about to be developed. They’re transplanted onto this mitigation restoration site. And then nursery container stock – little 1-gallon, 5-gallon plants of native species are planted, and the site is watered, and it grows. We kind of think of this as shake-and-bake habitat. And after a few years, the vegetation can grow quite tall and can really be taking on the attributes of the mature habitat that you saw earlier in the presentation. So this can happen very quickly, and vireos will follow this and move into it and nest successfully. Habitat restoration is a bit of a twist on this, where earth-moving equipment or foliar spray, or sometimes both, are used to work around existing willows and existing patches of riparian habitat to remove big globs of giant reed and to try to open up the space to allow the natives to get re-established. These sites are often then planted with nursery stock or with cuttings. Sometimes the giant reed is used to mulch those. And, again, they’re watered and cared for for a few years while they get established. One of our questions in our work monitoring this has been, you know, this looks quite different [chuckles] to vireos returning from Baja to nest. And, you know, we’re questioning, is there – what’s the short-term response of birds to this? We recognize that ultimately, the goal is that it will fill in, and it will achieve the characteristics of natural habitat, but what happens when they first come back and see this? Well, we’ve been monitoring a number of sites like this at Marine Corps Base Camp Pendleton. I don’t want work for Marine Corps Base Camp Pendleton, but they do have great leadership and a very strong conservation program, where they are – one piece of it is to systematically remove Arundo from all of their wetlands on their 125,000-acre base. So that’s a big job. And they are – they’re doing a really good job at it, and we’ve been partnering with them to monitor that to see how it’s working. So what you’re looking at here is time. The average number of territories per hectare – so we’re using territory density as our metric here. And we’re comparing the vireo density in these giant reed removal sites in the dark blue – or what will become the removal sites once the removal happens – to some reference sites. We always use reference sites in our studies because things vary from year to year for other reasons. And so, with reference sites, we can differentiate between the response, for example, to the giant reed removal as opposed to something about the weather or something that’s unrelated to it. And so what we were seeing before – I’m sorry. I keep losing my cursor. I’m trying to do a good job of using the onscreen cursor for those of you at your home in your jammies and slippers because I know you can’t see if I point to the screen. But I keep losing it. The giant reed removal took place in 2008. What we were seeing in the years leading up to that is that vireos were really disappearing from those sites. They were so choked out by giant reed. And compared to the reference sites, where vireos were persisting and doing quite well. So, after the removal, we did see that the number of vireo – the density of vireos at those removal sites was quite low compared to birds in the same year in the reference sites. But, within one year, those densities were comparable. And, in some years, the density was even higher in the removal sites – comparable, a little bit higher. So what we saw is a very quick response. Depressed numbers for a year or so, but then the vegetation comes in, and the birds respond very quickly. So that’s very encouraging, especially for a bird that only lives two or three years. They don’t have a lot of time to mess around. So this timeframe of a response was very relevant to their lifespan. So the result of cowbird control and habitat restoration has been that populations of vireos in California has increased at least 10- to maybe 15-fold over this time period. And I’ve left this estimate at 2010 for a couple of reasons. One, it was the high point in recent years, but in the remaining minutes of my talk, I want to talk a little bit about what’s happened since then and where we’re going now as far as the recovery priorities. But not only were vireos increasing in abundance and approaching a recovery target, they were increasing in range as well. So these little pinpoints represent locations where least Bell’s vireos have been detected in recent years. And this slide is not up to date, but it makes the points that I want to make, which include that birds have dispersed into the Los Angeles Basin. And that’s a formidable obstacle to a small, migrating bird that sees, you know, the L.A. Basin [chuckles] and is looking for a place to land or to settle and breed. So they’ve overcome that. But I want to point out that vireos now are up by my alma mater, UC-Davis there, in the yellow bypass near Sacramento. And they’re in my backyard – my childhood backyard. And, interestingly, they’re in your backyard. [laughter] We had a sighting of a least Bell’s vireo at the Bayfront Park here several years ago. It didn’t breed, but it got there. In fact, many of these don’t breed. But they’re at least making it there. And then some of the populations where there was breeding, you know, there was just a pair. Then after a couple of years, they die and were not replaced. But this is a really important first step to getting birds out into the historic range and then getting enough of them to be able to take hold and recolonize the range. And many of these birds are banded birds, so we know exactly where they came from. We can imagine how they got where they got. And so this gives us really good information on dispersal capability of these birds. Okay. So what are we looking at now? For the next 30 years – or hopefully not for the next 30 years. What are the threats that we’re facing? I want to illustrate the first one just by showing you a simple graph of the number of young fledged per pair over time at one of our study sites. And you see that it varies from year to year, but most years, it’s kind of above two – remember that number that we like to see. This is a somewhat growing population. And then, what happens in 2014? Does anyone remember – anyone know if year 2014 was like ours in southern California?
- Wasn’t it a drought?
- Yeah. This was an extreme drought year. And it came on the heels of some previous drought years. It was very hot during the summer. It was a really, really bad year for riparian birds that – well, not even just riparian. Bird productivity in general was really low that year. And these vireos barely got half a young per pair out. So we know that drought is – has a serious negative impact on productivity. And remember, I said it doesn’t take many years of productivity this low for a population then to really start plummeting. So drought is something that, you know, takes a – takes a woodland that might look like this and turns it into this. Many of these cottonwoods, for example, didn’t even leaf out at the beginning of spring. Or, if they did, they dropped their leaves in the middle of summer. Which that doesn’t work for a bird that gets food by gleaning for insects off of leaves. And this is not what you would call concealing nesting habitat, by any means. So drought is having a serious effect, and we’re having more frequent droughts. And we’re having sequential years of droughts. Connected to that, we have another new threat – wildfire. Now, typically, wildfires occur in upland habitats like coastal sage scrub and chaparral, and of course, forests. They usually don’t get into the wetter riparian systems. But that’s been happening more lately. There’s a big information gap about the effect of wildfire on riparian communities, and so we’ve stepped into this opportunity to learn more about that. This is a wildfire at Camp Pendleton. I think you’d agree this doesn’t look like vireo habitat anymore. We’ve been monitoring sites like this over time. So this is the site, you know, within the first spring season after the fire. The fire was in October. Which used to be the fire season. Now the fire season is year-round, right? So this was in ... Whoops. Where am I? There we are. This was in the spring after the October fire. Here we are a year later. It’s looking better. And here we are two years later. That’s looking great. This recovery took place against a background of normal precipitation during the winter. What we’re looking at now in some of our more recent studies is recovery that’s taking place against the background of a drought, and it does not look like this. It does not happen that fast. So wildfire and recovery from wildfire and drought are definitely intertwined. And, as you know, both of those are elements of the – of what’s projected as our future climate – the future climate that we’re already getting a taste of. And so the interaction – each of those by itself, and then the interaction between the two is likely to have great effects on vireo habitat, which will then translate into effects on birds. Happily, when conditions are good for recovery, vireos can respond very quickly. Again, as we saw with the weed management. And they will find these sites and nest in them. So they can respond quickly. Another threat that’s just come to our attention in the last couple of years is that of the invasive shot hole borer. This is a little beetle that bores these little tiny holes into willows and just about every species of riparian tree. And it cultivates a fungus that lays its eggs in, and then the young – the larvae feed on that fungus. And it’s the fungus that kills the trees. They can’t transport materials up and down the length of the trunk. And the trees collapse. The branches fall. The trees die. And it turns a site that looked like this at the Tijuana River in the summer of 2015 into this. [chuckles] Just a few months later. This is horrific. This is devastating. This clearly is not vireo habitat. So there currently is no treatment for the shot hole borer. There’s no way to control it. And we are already – we’re on high alert. We’re already seeing it start to spread to other areas in San Diego County and Los Angeles – the Los Angeles area as well. So this is something that’s capturing a lot of people’s attention. Okay, and then finally, quickly, what’s happening on the wintering grounds? There’s an emerging discipline in conservation called full life cycle conservation. And this is built on the recognition that migratory species only spend half their year on the breeding grounds and the other half on wintering grounds, which are often in another country, as is the case here. So we have a bird that breeds up here and winters 1,000 miles down here, where it’s not protected by our laws or our efforts or what have you. Nevertheless, there are threats on the wintering grounds that we need to know about. So full life cycle conservation is looking at the seasonal connectivity of breeding and wintering sites. One question we have is, do all the birds that breed here at Camp Pendleton, for example, all winter together here in San José del Cabo? Or do they just sort of spread all over the peninsula? That has implications for, really, the issue of, do you have all your eggs in one basket, or do you have them spread out? When you have all your eggs in one basket, and something happens to that basket, you have a bigger problem than when you have a more diffuse situation of birds not tightly connected. So this is a really important thing that we’re looking at. We’re looking at the factors that affect the birds’ survival during the winter. And the effects of their experience during one part of the annual cycle on another. So, for example, how does your experience during the winter translate into your ability to migrate back and breed? Or, how does your experience during a breeding season, for example, during a horrible drought year when you don’t have enough food and you haven’t produced any young, translate into your ability to migrate to the wintering grounds and find a place to winter? I have so much to say about Baja [chuckles] that I’m not going to get to say tonight. I’ll just point out that we are monitoring – I have established monitoring populations in the cape region. And we go down there a couple of times a year to be piecing together that information. So I’d be happy to talk more about this after the talk. So most talks have to end with the obligatory sunset shot. [laughter] When you study birds, it’s the obligatory sunrise shot. [laughter] I hope that I’ve been able to share with you the role that USGS is playing in endangered species management and recovery. Yes, we have a lot of challenges ahead, but we’ve also had a lot of successes. And I feel hopeful because there’s no shortage of dedicated, committed people who are approaching these questions with creative solution-oriented energy. And I’m very honored to have worked with so many of them over the years. I want to acknowledge and thank the sources of funding that we’ve had and all the students and field assistants. And thank you very much. And I’d be glad to answer questions. [Applause]
- Thank you, Barbara. I’m going to ask for folks with questions that they please step up to this microphone.
- You mentioned the 2.0 magic number to make sure the species, or the population is not declining. It seems like that ought to be two over the life of the pair, not two every year. But maybe they only breed for one year.
- Well, right. And it’s not exactly – two is an estimate. It’s not exactly two, depending on the longevity of the birds and so forth. But it often is the same thing because so many birds only live for one breeding season. So – but that’s a good point. It does need to be tweaked to take into account how long the bird is expected to live and how many young can it produce over that lifetime.
- Yeah, thanks for the talk and for coming up. So I graduated also from UC-Davis, and I’m – I can’t believe that you were inspired by Putah Creek to work on riparian habitats. [laughter] But how do you catch these birds to band them?
- In netting.
- We put up what are called mist nets. So these are very fine mesh nets that are suspended from poles. You can suspend a 12-meter net. We have 6-meter nets. We sometimes use 2-meter or – you know, very short nets, depending on what we’re doing. Generally, we’re going after males. And so we will play a recording of the male’s song near the net. The male will hear an intruder in the territory and come zipping out to see what’s going on and fly into the net. And then we take it out and quickly band it and let it go.
- Not too much trauma.
- No. Not too much trauma to them. Sometimes to us, though. [laughter] And then, with females, it’s a little trickier. We set up passive nets in the path that they use to fly to their nests. So they will – you know, the – both the male and the female will incubate the nest, and they will occasionally then have to leave and go foraging. So we just try to put up a completely quiet, passive – we don’t try to do any attracting or anything of the female. We just place the net where we’ve observed that she’s likely to fly and get her.
- Okay. Thank you.
- You’re welcome.
- And, as a word of encouragement, I’m replacing our lawn with California-native flowers for the butterflies.
- The endangered checkerspot.
- As well as the – some shrubs for the birds.
- Good. Do you live in Davis?
- No. I live here in Menlo Park.
- Oh, okay. Thank you.
- One of your – one of your last pictures was showing the wintering range.
- The – to the northeast of that is the next subspecies of Bell’s vireo, right?
- In Arizona. Is it – is it being more successful? And is there any gene flow going between those two populations?
- Well, so I don’t think there’s gene flow going between breeding populations in Arizona on one side of the Colorado River and in California. There’s that desert zone right along our eastern California boundary that I wonder about. And we’ve been doing – collecting some genetic samples to try to get at the question of, what is going on in that border region, and what is – what is the subspecies that’s along the Colorado River? Right now, it’s considered to be least on the California side and Arizona on the other side. We occasionally see Arizona Bell’s vireos in the tip of Baja during the winter. And we recognize them by their more yellow plumage. For the most part, though, it’s just the least Bell’s vireo that’s in Baja. And then the other subspecies of Bell’s vireo are in mainland Mexico or, you know, closer – due south of Arizona. So …
- I have a completely different question. It’s my understanding that the southwestern willow flycatcher is actually breeding in tamarisk.
- And so this is a case where endangered species is – you don’t want to then pull out all the tamarisk and there would be a danger to the endangered species. And I was wondering, is there – has there ever been a sign that least Bell’s is – will use other kinds of plants, other – you said giant reed already, you said no.
- Yeah. They don’t use – I mean, there – we might have one out of 500 nests placed in giant reed. So essentially, vireos don’t use that. They will nest in things like poison hemlock, which is an exotic herbaceous species. I think – we have occasionally had nests in something like a young pepper tree. But pepper trees are generally not – they’re not very – there’s not a lot of them. Tamarisk doesn’t really occur – they’re not using tamarisk to any extent. Certainly not like southwestern willow flycatchers are, which often seem to use it preferentially.
- Yeah. Well, thank you.
- So they – vireos will nest in mustard after a fire or a flood, for example, when the mustard is very robust, and it’s – you know, it’s tree mustard. It’s 3 meters tall. They can find a fork in a mustard, and they’ll make do with that. But that’s not a routine thing. But nothing like what you’re describing for southwestern willow flycatcher, where there’s a conflict there.
- I’ve had – I once had a manager tell me – he was trying to promote tamarisk eradication on his lands that he managed, and he said, I’m going to make things better for willow flycatchers, and I’m not going to let them get in my way of doing it. [laughs] Because there was concern that the flycatchers were using the tamarisk that he wanted to get rid of. But he wanted to get rid of it to make things better for them. So …
- Well, we have a similar problem in the bay with the invasive Spartina and some early evidence that the – that the Ridgway’s rail is more successful in the invasive Spartina.
- And so, you know, it’s this whole thing of, we can’t go back.
- So I don’t know.
- Whatever works works.
- Whatever works works.
- And sometimes we just have to listen to what the birds are telling us they need, not what we think they should need.
- Thank you.
- Hi. First, thanks again for your efforts to getting up here today.
- You’re welcome.
- And a number of us birders were able to see that Bell’s bird that was here eight years ago.
- So that was pretty exciting.
- But two questions about the black – or, cowbird mitigation. So, just curious, what happens to the females that get removed from the traps? Are they destroyed?
- They’re humanely euthanized.
- Okay. And …
- Sometimes they’re held and then they’re released at the end of the season, but I don’t think that that’s very practical or very common.
- And this would probably be more work than it’s worth, and I’m just curious. I understand that they don’t – or, the cowbirds don’t typically lay a second egg in a nest that already has one cow egg – cowbird egg. Has any work ever been done to put out decoy nests with cowbird eggs – or, fake cowbird eggs in them already so they won’t lay?
- Well, we actually find that they will – we will find two and three cowbird eggs …
- Aha. Okay.
- … in a single nest. And it may be multiple females coming along, and it doesn’t make a lot of sense when you figure out the math that they must be using. But we do find nests with multiple cowbird eggs. And if they are from unrelated females, that sets up some conflict [chuckles] right there among the cowbird young. So it may just be an artifact of really high cowbird density and not enough hosts, and they just put their eggs wherever they find a nest.
- Okay. Thank you.
- I got one more. You talked about – I’m talking – asking about the vegetation – the good plants versus the bad plants. And they don’t like to nest in the bad plants, but what about eating – is it eating the plants or eating the insects that eat the plants? Does that factor in as well?
- Well, one thing we know is that tamarisk does – saltcedar supports a lot of food. So vireos will feed on it. And it would – I’m not sure that giant reed supports much food. Because it just doesn’t have a lot of foliage cover like these other plants do. But it would be surprising – other than giant reed, that you wouldn’t have food associated with just about anything, and birds aren’t necessarily going to be discriminating that, oh, this is an exotic. I’m not going to eat here. [chuckles] And especially the herbaceous exotics and the flowering herbaceous species have lots of food associated with them. Many of those herbaceous species dry up very early in the summer, though, as well, and probably don’t have a sustained – can’t be used as a sustained source of food. But they flower and have lots of insect life.
- Well, it looks like it’s about time to wrap up. [laughs] I want to thank you all for coming. I want to remind you to please come back for our January 24, 2019, lecture on California’s changing ecosystems. Please save the date. And please, let’s give Barbara Kus one last big round of applause.
- Thank you, Barbara.
- Thank you.
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