If you’ve ever traveled to the far southern reaches of Arizona, near Patagonia on the Mexico border, you know you’ll find a region that looks different than the dry, rocky, saguaro-laden desert of metro Phoenix.
There are grassy fields, tree-covered mountains, desert scrub and riparian preserves. In fact, it’s one of the top biodiversity hot spots in the world, especially for birders.
"On the Patagonia-Sonoita Creek Preserve, we have over 270 different bird species that have been documented here. ... And part of the reason for that is we sit right in the middle of a number of flyways for migrating birds," said Aaron Mrotek, Patagonia-Sonoita Creek Preserve manager for the Nature Conservancy.
He said the region turns out to be pretty perfect for birds on their migrations north for the summer or south for the winter — think of it as a sort of rest stop for them.
But those all-important rest stops are in danger now — as climate change threatens these delicate ecosystems. The Show spoke with Mrotek about why this region is so perfect for migratory birds.
Full conversation
AARON MROTEK: We sit in an area called the Madrean Sky Island ecosystem through here. So we're sitting like in this kind of Sonoran Desert eco-region. But within that eco-region we have all these mountain ranges that pop up. And of course that's giving you different elevation gradients that give rise to different habitat types.
So because of the very differentiated habitat types that we have through here, it allows for various bird species that rely on those very specific habitat types to all find their individual ecological niches to be able to thrive, and move through this area, and continue on in their life cycles.
LAUREN GILGER: That's amazing. So this kind of idea of a stopover, like a rest stop for birds as they're migrating and the reasons they're drawn, these are really important for birds and for those migration patterns, right? Like if they don't have those rest stops, it can be a problem.
MROTEK: Absolutely. That's spot on. In particular in this area that we sit in. We're at about 4,000 feet of elevation here in Patagonia. And so we are right in the middle of that transition zone between kind of that lower Sonoran Desert eco-region, which is generally characterized by our iconic saguaro cacti. But then, up above us in these mountain ranges we have Douglas fir forest, pond ponderosa pines, mix oak woodland, chaparral zones.
But I think one of the really big distinguishing features about our area is that we have a perennial stream that runs right through the middle of it, and that's Sonoita Creek. So Sonoita Creek runs approximately 12 miles, and there's surface water throughout that entire 12 miles there. And, you know, In the desert, water is life.
It's not just life for people. It's also life for birds and mammals and reptiles. And so really, that surface water availability really creates a profoundly important habitat through here for those animals that are migrating to be able to access that water for their stopovers.
GILGER: OK, so tell us some of the species that come through. I know you're not like an extreme birder here, but that you enjoy or that folks are really there for. Are there really outstanding highlights that people come to see every year?
MROTEK: Yeah, well, while I'm not an extreme birder, I do associate, and I'm around extreme birders all of the time. So I can fortunately name a couple for you here. You know, there's a number of different warbler species that are really iconic in this area for migrating species coming through here. For instance, Lucy's warblers, those just showed up here on the preserve, and they really tend to enjoy our mesquite bosque habitat type through this preserve, through here.
But one of my favorite birds that migrates here every summer is the gray hawk. OK. ... gray hawks have very specific habitat requirements. They really like riparian zones with field habitats adjacent to those riparian zones. And that really characterizes the Patagonia Sonoita Creek Preserve, which I'm sitting at here right now. We have that riparian ecosystem moving through here with these big grassland fields that surround it.
So it's really the perfect habitat type for these gray hawk. And gray hawks ... they're more commonly found through much of Sonora, Mexico, and down south of that as well. But the northernmost range is right around here in southern Arizona. And so as a migrating species, to be able to see that species that you would most commonly see in Mexico coming up into the United States, I think that really makes it super, super unique.
And people, again, travel from all over the world to come to this area of the world to be able to view that gray hawk, to enjoy it in its natural habitat.
GILGER: Yeah, that's amazing. ... So, I mean, these kind of rest stops, these stopovers for these migratory birds, though, are becoming harder to find, it sounds like, especially when it comes to those incredibly specific ones, they can be like for the gray hawk you mentioned.
I mean, what happens when one of these rest stops disappears? Are we seeing this happen in southern Arizona?
MROTEK: Oh, absolutely. You know, in southern Arizona we're seeing a long-term trend of drier winters and reduced monsoonal precipitation. And we're also combining that with increased water consumption in the state of Arizona by a growing human population.
And that's causing many of our once perennial streams to start to run dry, resulting in the loss of not only the valuable aquatic habitat, but maybe more importantly for a lot of these migrating birds, the associated riparian habitat that would be found alongside of these stream ecosystems.
And, as I mentioned, water in the desert is life, but is also our greatest limiting resources. And climate models suggest that Arizona may continue to see reduced precipitation annually throughout our entire state. And so we're seeing that reduced precipitation. We're seeing warmer daytime and nighttime temperatures. Which are stressing these natural ecosystems and creating optimal conditions for things like wildfires or pest, insects or diseases or invasive species to come into these areas that were once really, really important stopovers and still continue to be.
But we're seeing those stresses start to result in ecosystem conversion where vegetative communities are slowly being replaced by species that are suited to a warmer and drier climate. Ultimately, these conversions can result in habitat shifts, leading to the replacement of entire wildlife communities, which is really concerning for the long-term sustainability of these migration stopovers throughout the entire state of Arizona.
GILGER: Yeah. So let me ask you lastly, Aaron, like the, the question, I guess, that drives this home for folks, because I know we talk a lot about water scarcity, we talk a lot about climate change and warming weather. And I think a lot of folks will say, you know, we can't worry about things like migratory birds when we have to worry about, you know, human beings having these kind of resources going forward. But there are, when it comes to these species, broader ecological questions at hand, it sounds like.
MROTEK: Oh, absolutely. You know, I think I tend not to be focused on single species. ... I tend to think of our ecosystems as really, really complex processes. Really what we're starting to see is an upset in the balance of these really, really complex systems that we call ecosystems down here.
And fortunately, there are a number of solutions. ... Some of those solutions might look like conserving a variety of habitats. We're looking at restoring and maintaining those diverse habitats to support broad species assemblages. And really what we also seek to do is implement long-term monitoring protocols for vulnerable species, in particular migrating vulnerable species and their associated habitats, and to inform adaptive management.
So these are some of the things that we can think about doing to preserve these really, really important flyovers or stopovers for migrating species across our entire state of Arizona.
GILGER: OK. Well, glad it's not hopeless. It sounds like. All right, we'll leave it there. That is Aaron Mrotek, Patagonia-Sonoita Creek Preserve manager for the Nature Conservancy, joining us to talk about stopovers from migratory birds. Aaron, thank you very much for coming on The Show. I really appreciate you being here.
MROTEK: Oh, you're very welcome. Thank you so much.
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