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Ducks Unlimited Podcast is a constant discussion of all things waterfowl; from in-depth hunting tips and tactics, to waterfowl biology, research, science, and habitat updates. The DU Podcast is the go-to resource for waterfowl hunters and conservationists. Ducks Unlimited is the world's leader in wetlands conservation.
Mike Brasher: Hey, everybody. I am Dr. Mike Brasher. I'm going to be your host on this episode. We are continuing a conversation that we started on the last episode with Dr. Ben Luukkonen and Dr. John Colussi, covering in some pretty interesting detail, a recently completed research project into mallards in the Great Lakes region. And so we're going to get right back into it. So welcome back, Ben, John. It's great to have you again.
Ben Luukkonen: Thanks for having us back, Mike. Thanks, Mike. Looking forward to talking more.
Mike Brasher: Ben, I think what I want to do to sort of expedite our conversation here, I'll give people sort of the high-level overview of some of the methods that you use in terms of capturing these mallards. You can kind of add some details about where and how you went about selecting them, but people will have heard some recent conversations similar to what you did in terms of the transmitters and so forth. These are, you used, backpack-mounted GPS, solar-powered tracking devices that are able to record locations and movements at incredibly fine scale. I think I was looking at your presentation, you shared over four and a half million GPS locations from 592 female mallards that were marked over this three-year period. That's pretty incredible. Did these units have the accelerometer in them the way some of the others did? So tell us a little bit about that, I guess. I'm not sure how well we covered that on a previous episode with other researchers.
Ben Luukkonen: Yeah, so in addition to the GPS component, there's this device called an accelerometer within the transmitter, and that basically measures acceleration in three dimensions. And so that allows us to look at the physical position, of the transmitter, as well as how much that transmitter is moving. And oftentimes researchers are interested in those accelerometer data to look at bird behaviors.
Mike Brasher: So one of the next big things to talk about here is where you captured and marked these birds. One of the most fundamental concepts in any type of rigorous experimental design is to ensure that whatever it is that you're studying is done so in a way that is representative of the larger population that you're trying to draw an inference to. And so in this case, we're talking about Great Lakes Mallards, and you've kind of already identify that there's these different, we see these different, I don't want to say group, but we see different behaviors in mallards in that geography, behavior meaning in this case sort of where they are, their tendency to be in urban areas versus more rural areas. And so if you're wanting to draw an inference to that entire population, then that means you kind of got to target all of those different situations, right? So tell us about that and how important in the design of all this, when discussing it with the partners, how important was that and what kind of calculus went into figuring out how you were going to do that, capturing birds out in these sort of non-urban areas, but then in the urban landscapes as well.
Ben Luukkonen: Yeah, so broadly our goal was to mark a sample of female or hen mallards that were representative of female mallards nesting in or just more generally using the Great Lakes region during the breeding period. And we had five states partner on the research, which included Michigan, Wisconsin, Illinois, Indiana, and Ohio. And even though we don't have annual aerial surveys in those Southern Great Lakes states, we were still interested in mallards in those states, particularly birds using urban areas in those landscapes. And so broadly, we deployed transmitters across those three states, and we did so in proportion to estimated breeding mallard abundance by bird conservation region. And I don't think we need to get too in depth on what those are, but there's three primary BCRs, or bird conservation regions, in the study area. And they just broadly characterize landscape conditions in bird communities. And maybe what listeners are most interested in is that the highest breeding matter densities occur in southern Michigan and southern Wisconsin within that landscape. And so the majority of our transmitters were deployed in that BCR, but also up into northern Michigan. In the UP, northern Wisconsin, and then down in those three southern Great Lakes states as well. Then on a more fine scale, we had this question again of, do behaviors and demographics differ between mallards that use urban versus rural habitats? And so we attempted to split our transmitters 50-50 between mallards captured at urban or developed sites and mallards captured at rural sites.
Mike Brasher: And Ben, remind me when during the year you marked these birds. Was this like a late summer, early fall capture period?
Ben Luukkonen: Yeah, we primarily marked birds during the traditional preseason banding period, which is July 1st through September 30th. And so we were able to take advantage of a lot of the mallard banding that goes on every year during that period for annual population monitoring. So approximately 80% of our GPS marked birds were marked during that July 1 through September 30 time period. But we did mark about 20% during the spring or from March 1st through the end of June. And that was primarily to increase the number of birds that we had available to monitor during the breeding period.
Mike Brasher: So we heard John say he was able to get out in the field with you and capture a few birds. I guess you were out for some of the capture. Is that right, John? Capture and marking?
John Coluccy: Yeah, a few times got to drag my son with me and actually Derek Christians from. Yeah, from Campus Waterfowl, right? Campus Waterfowl was out and did a program with us too. We did a little bit of a podcast and he documented the project too.
Mike Brasher: That's right. That's right. Yeah. So go check that out. I'm trying to remember when that might've been. Was that last summer or two summers ago where he would have been up there?
John Coluccy: Last summer.
Mike Brasher: Okay. Good deal. Good deal. What about our good friend, Greg Souliere? He's another one that we'll have on a future episode of the podcast. We're kind of laughing here because the three of us know Greg very well. He's been a great friend, and I think, Ben, fair to say, he's been a pretty influential mentor for you. Don't know if that's a good thing or a bad thing. Kind of depends on which part of the Greg Souliere you get in the mentorship there. But no, I say that in jest. He's a great guy. He was and still is a very incredible waterfowl ecologist. He retired a few years ago. But were you able to get Greg out to help with any of this research?
Ben Luukkonen: Yeah, Greg got to make it out. He's been a longtime friend and mentor. First mentorship on how to set a field goose spread, and more recently, he does have a lot of expertise on waterfowl and wetland habitat management in the Great Lakes region. So he's been kind of involved in this project as well.
Mike Brasher: A lot of experience and stories and expertise in other areas that we'll leave off of this episode, but we can cover at some future time. But a lot of people like Greg, passionate hunters throughout that region, conservationists, waterfowl managers. I'm really, really interested in this work and making it happen. And so I want to transition now, and Ben, I guess the other thing that I need to say, we need to tell people in terms of methods, is that when you captured these birds, you drew a little bit of blood. That's where you got the genetic information, and that would tell you, I can kind of abbreviate some of this. That basically, through the work in Phil's lab, he would be able to tell you sort of the percentage of game farm ancestry and the percentage of wild mallard ancestry in each of those birds. Folks that are familiar with duck DNA would kind of know how that works. When you get these results back, you get sort of a percentage assignment to each of those groups of birds. It could be a 75% game farm mallard genetics and 25% wild mallard genetics, or it could be the other way around, or it could be 95% wild mallard ancestry and some 3% or 5% game farm, and representing different levels of hybridization through the years for the birds that you're marketing. That became a very important part of this where you wanted to look at different behaviors and different survival rates and all sorts of other metrics between birds that fell along this gradient of ancestry from pure wild to having a high percentage of game farm genetics within their genes. So, did I get that right? Summarize that sort of correctly?
Ben Luukkonen: Yeah, it's absolutely right. So a very important covariate in our analyses was the proportion wild genome or maybe more accurately proportion wild ancestry. And just like you said, it could be 95% wild, it could be as low as 10%. wild. And then in addition to that, we could also look at generational backcross categories. And so we could say, this was a pure wild mallard, but maybe we have a hybrid. And we could say, well, this is a first generation hybrid or an F1, meaning that one parent was a wild mallard, one parent was, in our case, a domestic game farm mallard. And so that F1 hybrid would have about 50% wild genes, about 50% game farm genes.
Mike Brasher: And we have had discussions with Phil on a number of times about what he's finding. And then the logical question is, well, what are the implications for mallard populations at a large scale? What are the management implications for those findings? Your research is an important step in that direction. Doesn't provide all the answers. It provides some information that we can use to better understand this situation. And we'll kind of, as we wrap up this conversation a bit later on, we'll talk about what some of these key implications might be. But for right now, Ben, lead us through some of the key findings from, if you want to just jump right into Mallard Movement's resource selection, that's kind of your chapter two with that methodological background, some of what we're trying to answer. What were some of the key findings at a high level from that particular chapter?
Ben Luukkonen: Yeah, I think I'll start with what we found for genetics and then what that kind of translates to or looks like for behaviors and movement. So I think you mentioned we marked 592 female mallards with transmitters across the region and genetic sampling of those individuals revealed that 56% of those birds were hybrids, so crosses between wild and domestic game farm mallards. and 44% of those birds were actually wild mallards. And so right off the bat, that was probably one of the most surprising outcomes, certainly to me, of the entire research project is just how many hybrid mallards we encountered in our sampling across the region, that distribution or that breakdown between wild and hybrid birds did vary by the capture site type. So at rural sites or what we would think of as more traditional rural wetland habitats, Mallards captured at those rural sites were 56% wild and 42% hybrid. But at urban sites, the hybrids were way more prevalent. And of birds captured at urban sites, 78% were hybrids and 22% were wild mallards. And so that stood out to us. right away.
Mike Brasher: That's really interesting. I was kind of wondering about that. I mean, so number one, it's amazing that you got almost a 50-50 share in each of those categories, wild mallards and hybrids. And I was also wondering, and you answered it, how many How many hybrids did you see in those rural kind of non-urban landscapes? And it was about, again, about 50-50, which is, I don't know, maybe surprising. Were there any kind of generational differences there? Did you look at that? To what degree did it being an F1 or F2 or F3 hybrid influence their tendency to be in those different locations?
Ben Luukkonen: Yeah, we found very few, I want to say less than five hybrids that had less than 50% wild genes at rural capture locations. So in other words, the birds that were most domestic were captured in urban areas.
Mike Brasher: Okay, yeah, that seems to make sense there. So, all right, you've got your sample of these birds here, and you've got them identified based on their ancestry. And what were some of those key behaviors and metrics that you were trying to capture from them?
Ben Luukkonen: Yeah, the two main Well, I guess there's three main. We'll start with kind of the movement ones. We were interested in both local movements and migratory movements. And so the transmitters allowed us to look at both. And what we found is that wild mallards moved significantly farther daily distances than hybrid birds. So wild mallards were over two times or moved two times the distance than the most domestic birds. and moved about 1.3 times as far as first-generation hybrids. And so the more domestic ancestry a bird has, the more sedentary it is, and the shorter daily distances those birds move. We also found differences in the tendencies of birds to migrate. Wild mallards were over two times more likely to migrate than first-generation hybrids. and about one and a half times more likely to migrate than second generation hybrids. So birds with more domestic ancestry are more sedentary on a local scale and less likely to migrate. And that certainly raises concerns about their ecological fitness and their ability to be successful surviving and reproducing
Mike Brasher: Ben, I'm looking at a graph that you shared, you used in your presentation, your defense presentation, and it shows that relationship between the proportion of wild ancestry and that daily movement distance. And you've got all these probably 590 or so dots, 500 plus dots in here representing the average daily movement distance for each of these birds. and it kind of is related to the proportion of wild ancestry. There's a lot of variation in that spread at some levels along, but the thing that is so dramatic and really jumps out at me is for these birds that are less than 50% wild ancestry, in other words, more than 50% game farm ancestry, The degree of movement, there's not as much variation for that group of birds. They don't move very much at all, and they're the ones that are going to be in those urban environments mostly, right? But then once you get up to about 60, 75% wild, and those would be birds that had backcrossed. Their ancestor had been, let's say, a true hybrid, F1 hybrid, but then they would have backcrossed with a wild mallard. and as more of those wild mallard genes get back into their offspring, that movement distance begins to more closely resemble that of truly wild mallards. Did I get that right?
Ben Luukkonen: Yeah, that's right. More specifically, we found that the third generation hybrids actually moved similar distances on a daily or a local scale as wild mallards and generally had similar to tendencies to engage in fall migration.
Mike Brasher: This is really cool to see. This is just so fascinating to see now linking some of these behaviors to the genetics. It's a puzzle that Phil and his team and others have been putting together for a number of years. If we go back far enough, we would talk about introgression of mallard genes into black ducks, the black duck population, the introgression of mallard genes into model ducks. And we didn't think we would be able to recover that pure mallard or pure model duck or black duck ancestry or kind of genetic signature whenever that started happening. But what Phil and his team found is that As long as there is a large enough parent population of either black ducks, as was the case then, or model ducks, and those hybrid offspring have the opportunity to backcross into that parent population of the pure species, what they found was eventually that genetic signature would return to more closely resemble that of the pure population. And so, your study is finding not only is that true, but also some of the behaviors that you're measuring are also reverting back to those sort of shown by that truly wild population. I kind of struggle to explain that concisely, but that's essentially what's happening here, right?
Ben Luukkonen: Yeah, and I think if we're interested in maintaining wild mallards, this is a good thing because this shows that Maintaining a sizable population of wild mallards would allow these more domestic traits to eventually be bred out of the population under the assumption that they're maladaptive as long as we have enough wild mallards left in the population to kind of buffer that domestic genetic signature.
Mike Brasher: So you talked about the fall migration tendencies, wild mallards being more likely to migrate than those hybrids. Anything more specific to kind of draw out of that? You've had this conversation with a number of people. They ask you all the cool questions. I'm not going to be able to have all those come to mind right off the top of my head, or I don't have them written down either. But anything else, like some of the more notable findings you wanted to share or the more common questions you need to answer?
Ben Luukkonen: Yeah, on the topic of migration, one of the other things we noticed is that even wild mallards marked in the Great Lakes really only moved as far south as it seemed like they needed to, to find presumably open water and available forage. And we had very few individuals, whether they be wild or hybrid birds, that moved farther south than the latitudes of Tennessee. I think we had one bird that went down to Arkansas and Louisiana, one each to North and South Carolina, about five to Virginia, four to Pennsylvania. But really, the primary kind of wintering strategy was either to move locally within the northern Great Lakes states to find open water. or just to migrate short distances to the southern Great Lakes states. So, Illinois, Indiana, Ohio, Kentucky, that kind of geography.
John Coluccy: Hey, Ben, did you get a genetic signature? You obviously did probably on that bird that went to Carolina. I was just kind of curious about those birds, where they fell on the spectrum. And if you're aware, there's another study going on in the East with Atlantic mallards or Eastern mallards. And we've got some birds marked over there from the Carolinas that are coming over to the Great Lakes. And of course, we're marking those in winter. And they're settling in places like Michigan. And they don't do very well. Actually, we had a bird, I think, come all the way over here from Maryland this year. it actually chose to nest right up against the house. And although it was in a rural area, semi-rural, it nested it in a flower bed and wasn't successful and ultimately got killed. So it's just a lot of interesting stuff going on there.
Ben Luukkonen: Yeah. So kind of broadly, we did not have any hybrids that were less than 60% wild that migrated over 30 kilometers. So all the birds that are crossing multiple state lines are 60% wild or greater. For the Carolinas, I'm not sure about the North Carolina one. The South Carolina one was more recent, and that was either a wild bird or very close to being wild.
John Coluccy: The other thing that's really interesting to me, too, is the spatial distribution of these F1 birds, those first-generation hybrids and how we might link that to to like what's going on there with maybe captive releases you know like you can envision you know you always go to a park or an urban wetland and you see ducks just don't look they look like park ducks right and it's like you wonder how they get there and it's like you know is that some of like people just you know they get a duckling at easter time and the kids get tired of it or they can't take care of it and they just dump in a park or how's you know kind of just thinking about mechanisms for how those things are happening we know there are put and take shooting preserves and things like that out there as well, more in rural areas and not associated with urban environments. But these are just things that have been swirling in my mind all along with the results of your work.
Mike Brasher: A whole new set of questions, John. That means you can't retire for another 20 years. You got to stick around, help us answer them. No comment from me.
John Coluccy: No, I keep, I muted myself there. I keep telling people that these data sets, you know, Ben's got like four and a half million GPS locations and all this accelerometer data. And it's like, there's going to be an opportunity to mine this data for questions that we haven't even thought of. You know, Ben's one human being, one individual, as talented as he is, he can't address everything. You know, there's lots of cool stuff going on with sanctuary use down south. use of safe and urban areas and there's just all sorts of things that we can be looking at with this data through time. So it's a really invaluable data set and I hope that, you know, we can invest in further students if Ben doesn't have the time down the road to start investigating these questions and just mine that data till we can't mine it anymore.
Mike Brasher: Ben, I want to kind of move us along here. One of the other things that you looked at in that kind of movement kind of realm was sort of habitat use. And I note here that mallards with greater game farm ancestry were more sedentary. We kind of talked about that, but they had greater use and selection for urban areas. Probably not too surprising. We've kind of hinted around that already a few times. So, yeah, in terms of are those birds well adapted to also survive in wilder locations, more rural locations and habitats? And that may… I don't know if your next chapters kind of address that. Let's just kind of move on to that. And you can tell me if from any of these results, you could kind of answer that. But next in the line of questions was sort of looking at nesting ecology. Um, and fidelity here. I'm not, you can kind of speak generally to fidelity to the extent to which it's a high priority for you here. But let's talk about nesting ecology and what you learned about key differences there between these groups of birds.
Ben Luukkonen: Yeah. So the combination of GPS and accelerometer data allowed us to look at when, well, I should say if, when, and where these hens initiated incubation, how long they incubated for, and for the birds that we weren't able to actually observe in the field in person, whether or not they were successful. And so we found in terms of the chances that a hen initiates incubation, wild mallards were over three times more likely to actually incubate a nest than were the most domestic or the feral category of hybrids. And so that's pretty concerning for productivity in that mallards with more domestic ancestry are less likely to engage in incubation behavior, meaning they're less likely to hatch eggs and produce ducklings.
Mike Brasher: That's a pretty important finding for trying to understand what's going on with mallards up in that part of the world, isn't it?
Ben Luukkonen: Yes, very, very important. And we might touch on it later, but kind of the other main data set we use was the banding data set. And we did find that productivity has declined.
Mike Brasher: productivity has declined over what time frame?
Ben Luukkonen: So, for that analysis, we looked at birds that were banded from 1991 through 2022, and we found that productivity actually really increased in the 1990s, but since the year 2000, productivity has been on a long-term decline in the Great Lakes.
Mike Brasher: Ben, with regard to the idea that hybrids were less likely to incubate a nest, that shouldn't necessarily… Well, when you think deeply about this and the source of those game farm birds, should we be surprised at that? Is there a potentially good explanation for why these birds may be laying eggs but not incubating them? I know you have some thoughts about that.
Ben Luukkonen: Yeah, there's been previous work on game farm mallards in captivity. And those studies have shown or suggested that game farm mallards have a longer egg laying period and actually tend to lay more eggs than wild mallards, which we might initially think, hey, maybe that's a good thing. They're going to produce more ducklings. But in captivity, those eggs would be very likely collected and put in an artificial incubator to maximize production in a captive setting. And so as these game farm mallards have been bred through many generations in captivity, Whether intentionally or unintentionally, those kind of genetic instincts, you might say, to sit on a nest and incubate eggs could have been lost. And so that could be one explanation for this lower incubation incidence that we see in mallards that have more domestic game farm ancestry.
Mike Brasher: Alright, so Ben, what about nest survival? One of the other things that you kind of measured there between these groups of birds, what are some of the highlights there? And then sort of close out this chapter for us. We want to try to move us along here and see if we can get to wrapping up here before too long. It's easy to talk about this stuff for like an hour and a half, two hours, but I'm trying to be disciplined, but it's hard for me.
Ben Luukkonen: Yeah, there's definitely a lot to unpack, but we'll try to just hit the highlights. So in terms of nest survival, or you could think of this as nest success, that does at least one egg from a nest hatch, we found that wild mallards primarily nested in more undeveloped areas, more of what we think of as being traditional mallard nesting cover, upland vegetation adjacent to wetlands, that sort of thing. And wild mallards on average had about 19% nest success or nest survival. The hybrids with more domestic ancestry primarily nested in urban areas, so that follows right along the trends we've been seeing in terms of their movement and habitat selection. They could have pretty high nest success, and in urban areas they had similar nest success to wild mallards. that nested in urban areas, but I think the key thing to remember is that few of those hybrid birds nested in the first place. And so although they can be successful nesting in urban areas, they should have lower contribution to producing ducklings than wild mallards.
Mike Brasher: Welcome back, everyone. I'm here again with Ben Lucanen and John Cluzzi, and we're going to wrap up this conversation, fascinating discussion. One of the other parts of this chapter related to a question we posed earlier on whether there is a movement of birds out of the Great Lakes, and maybe that's responsible for the declining trend we're observing from the survey data. This chapter also included some work to answer that. So briefly, kind of tell us what you found there. I'm looking at the results or at your conclusions, but share that with our audience.
Ben Luukkonen: Yeah, when we mark these birds, in addition to taking the blood sample, we took a real small clip of one of the wing or flight feathers. And via a technique looking at stable isotopes, that feather sample allows us to estimate roughly at what latitude the bird grew that feather. So for adults, that tells us where did they go through their flightless molt. And for juveniles, it tells us where were they hatched or where were they produced and grew that feather for the first time. It is a very kind of a rough latitudinal scale. There's not a lot of you know, precision there. But we can assess, you know, are birds we marked kind of from the Great Lakes or are they from other areas? And so we found that most of the birds we marked were indeed from the Great Lakes or that they molted or hatched in the Great Lakes. But probably more importantly, in terms of fidelity, we found that nearly all, 98% of mallards from the Great Lakes return to or remain within the Great Lakes into the subsequent breeding period. And so that suggests to us that fidelity of hen mallards to the Great Lakes is quite high, and we probably are not losing many female mallards to nest in other regions. And ultimately, that suggests that this decline is more likely a result of declines in survival or productivity, as we mentioned.
Mike Brasher: picture of survival and productivity across the entire Great Lakes mallard population, but just to make sure I ask the question, did you attempt to calculate survival rates for those different groups of birds, pure wild mallards and hybrid mallards? Is that factored into the population modeling that occurs in the next phase of this or the next chapter, I should say?
Ben Luukkonen: The population model just uses data from the aerial surveys and from banded and recovered banded birds. We did have a separate chapter on survival for our GPS mark birds. And one of our limitations there is that these birds with more domestic ancestry simply rarely use or don't use rural areas. that wild mallards are more likely to use. And so it's hard to compare survival apples to apples, so to speak. So in urban areas, the birds with more domestic ancestry can survive at similar rates. as wild birds. And we found that the primary sources of mortality were predation and hunter harvest. And so that makes sense, right? Because if a bird spends a lot of time in an urban area, that bird's probably subject to fewer predators and is less available for hunter harvest. But again, it was we weren't actually able to really estimate how do these more game farm birds do in traditional mallard habitat in rural areas.
Mike Brasher: Okay, I kind of thought that was the case, but I wanted to make sure we posed it because some folks may be wondering about that. So let's move on then to population dynamics, kind of trying to pull a bunch of pieces, different data sets together and identify which ones are more responsible for those changes in population trajectory. And so, we don't have to go through all the nitty-gritty of the type of modeling that you did, but I think it would be useful to kind of point out some of the data sets because hunters are a crucial role, many of which are going to be our listeners, play a crucial role in providing that data. So, tell us a little bit about this modeling effort and the data sets it relied on.
Ben Luukkonen: Yeah. So for the population model, based on our GPS data, we felt we could narrow the cause of the decline down to really those two parameters, survival or productivity, given that it appeared that emigration was low and fidelity to the Great Lakes region for female malaria was really high. And again, the primary data sources for this population model were those aerial surveys we talked about. And so that gives us estimates of mallard abundance each year during the breeding period. But I think probably even more importantly is the annual banding and band recovery data And that data set would just simply not exist, at least for the band recovery side, without the contributions of duck hunters. And so I think as duck hunters, we should be really proud of this huge citizen science project, one of the oldest and longest running citizen science projects in the world. And I just say that if you're a duck hunter and you harvest a banded bird, please report that band because that information contributes substantially to what we know about all waterfowl in North America.
Mike Brasher: Ben, I guess, again, sort of for the sake of time here, I'll let folks know that from an analytical standpoint, you used what we've referred to now as an integrated population model, which to me, I'm looking at it on the screen, has a lot of different fancy equations, things that I'm no longer able to decipher and understand. And so I'll just say that it represents some of the most current and comprehensive analytical methods that we have in the wildlife field to take advantage of all these different data sets simultaneously to develop a more comprehensive understanding of what's going on with our wildlife, in this case, waterfowl populations, and help us identify which of those vital rates might be most responsible for the changes that we're seeing. So with that, and you can add anything to that if you wanted to, but I just tried to describe that at a high level. With that, What were the key questions? I mean, I know you're obviously wanting to know if, is it survival that's driving this decline? Is it productivity that's driving this decline? Is it some interaction or is it something else that we can pull out of here? What did you find through this analysis?
Ben Luukkonen: Yeah. So broadly, there's kind of two levels of inference. One is just what you said. Is the decline in population size due more to survival or productivity or a combination thereof? And then the second level is, what are some things that have contributed to any changes in survival and any changes in productivity? And so those That level of inference more corresponds to those research questions we talked about. So on the survival side, we were able to partition the causes of mortality, so kind of the opposite of survival, into either mortality due to hunt or harvest, right? Because we know when bands are reported, were they shot by a hunter? Or were they recovered by other means? And also into natural mortality, so birds that died from causes other than hunting. And that's one of the things we didn't really talk about in our initial questions, but previous research suggested that harvest was not the driver of the decline. And we just wanted to simply reassess that with this model. On the productivity side, we had more covariates or more factors of interest. One of the main ones is the one that we talked about, and that's the loss of grassland habitat in the Great Lakes region, which we think is important for providing nesting cover. And so for productivity, we looked at the influence of the number of acres enrolled in the Conservation Reserve Program each year as an index of annual grassland abundance. We looked at the number of ponds or wetlands counted on the aerial surveys. And then at the banding site level, we looked at does the amount of developed land cover around banding sites affect how many ducklings are produced? Does the latitude of the banding site affect how many ducklings are produced? And then we also looked at does the total number of mallards, the population, affect how many ducklings are produced? So I think maybe I'll switch back over to survival and talk about the results. And I think
Mike Brasher: Before you do that, I have a question for John. So John, you and I both went through our PhDs a number of years ago, about two decades ago now. It's kind of difficult to say that, but does it strike you now that the level of questions, the number of questions, and the level of thought going into these? The number of questions and the complexity of those questions has just expanded pretty dramatically, you know, in recent years. And so we got folks like Ben and many others that are capable of tackling these. I mean, that's like, I think about some of this and I'm saying to myself, boy, there's probably two or three PhDs built into some of this list of questioning. Does that strike you too, John?
John Coluccy: Yeah, absolutely. You know, when I think back to the demographic model that I put together for the Great Lakes, it was much more simplified than this integrated population model. But surprisingly, some of the results are very similar in terms of drivers of population dynamics, which is really cool to see.
Mike Brasher: But just a little bit of insight for folks out there into some of the incredible graduate research that's going on these days. So sorry, Ben, take us back to where you were. I think you were going to talk about some of the high-level results from one of these. So take it away.
Ben Luukkonen: Yeah, thanks, Mike. I think I'll start with survival and just generally survival for both adult and juvenile female mallards declined. So survival for adults steadily declined over the time period of our studies, so 1991 through 2022. For juveniles, there was an even sharper decline early on, but then survival in more recent years has increased a little bit, but there's still been an overall decline in survival for both adult and juvenile female mallards. And so, right away, that helps answer the question, is survival contributing? Yes. But what I think is even more useful and more informative from this survival submodel is when we look at the causes of mortality. And so again, we partition that into harvest or hunting mortality and then natural mortality, which is all other causes. What we found is that for adult females, natural mortality was about three and a half to almost seven times greater than harvest mortality. And for juvenile females, that natural mortality was about 1.3 to 4 times greater than harvest. And so kind of at a broad scale, what that's telling us is that it's been environmental factors during the spring and summer portion of the annual cycle when most of the natural mortality occurs for female mallards, not harvest, that have driven these declines in survival. And then lastly, as a little bit of an aside, we looked at the effects of duck season lengths, bag limits, and the number of duck hunters on harvest mortality. And despite changes in all three of those, Harvest mortality for adult female mallards has been remarkably constant and low over about the last 30 years. And for juvenile females, harvest mortality increased when we had more duck hunters in the Great Lakes, but has since declined. And these recent liberalizations or increases in the bag limit from one to two hen mallards has really had no appreciable or noticeable increase on harvest mortality. And so that's a long kind of way of saying that these declines in survival are due more to natural mortality and harvest is not the driver.
Mike Brasher: That's probably surprising to some people. It's insightful to all of us. I'm looking at this graph here where you've got it broken down by adults and juveniles. The harvest mortality, annual harvest mortality for the adult females is right around 11%, if I'm kind of eyeballing this correctly. And then when we jump over to the first year birds, it varies from, let's say, 18%, maybe got up to about 25% during that time period that you were referencing had more hunters on the landscape. And then now in the past 10 or so years, it has dropped back down to right around 20%. harvest rate, harvest mortality for those young birds. And again, something that I'll just kind of add here, we oftentimes say that current evidence suggests that harvest is not driving population change in these populations, at least for most of them that we talk about. The important kind of caveat there is that harvest at the levels we're currently observing. We're always kind of careful to add that if you try hard enough and unregulated enough, yeah, you can overharvest any population. But the key thing is that at the levels we're seeing, it's not harvest mortality that's driving the ups and downs of these populations. And that speaks to the value of the the science-based regulations that we have in place governing our allowable take of waterfowl populations here in North America. So Ben, where does that take us? I guess we've dealt with the survival slash mortality component there. Anything to add to that or do you want to, in terms of potential causes, or do you want to jump over to kind of productivity?
Ben Luukkonen: I'll just add briefly on the survival side that This long-term increase in natural mortality is definitely a concern for female mallards, but kind of an opportunity for future research and currently an unknown is what has most contributed to that increase in natural mortality. It could be a combination of several factors based on other aspects of this research. It could be related to genetics, loss or changes to breeding or brood-rearing habitats, predators. But while this model is useful to identify that, we really need some additional specific studies to try to figure out what is driving this increasing natural mortality.
Mike Brasher: So what about productivity? Have we talked about that yet in terms of… I know we talked about it declining, but in terms of what you found regarding relationships between a change in the landscape and any other kind of spatial distribution of those productivity metrics?
Ben Luukkonen: Yeah, through time productivity has declined. Again, roughly from 2000 through 2022, there's been a steady decline in productivity for Great Lakes Mallards. And one of the most important covariates of the ones that we examined was that loss in conservation reserve program acres in Michigan and Wisconsin. Again, that probably represents a loss of grassland relevant to upland nesting female mallards. And so that is definitely a concern. The number of wetlands or ponds counted on the aerial surveys during this time period has remained relatively consistent. So that's perhaps a good thing, but this loss in upland nesting cover is concerning, and that's kind of the other part of the habitat equation that's important for mallard productivity. We also found that productivity varied spatially across the Great Lakes. And we found that productivity was lower per adult female in the southern Great Lakes and at urban sites. And so if we think back to our results from our GPS birds and their nesting, behaviors, that kind of lines up because we found the most hybrids in the Southern Great Lakes and at urban sites. And we found that mallards with more domestic game farm ancestry were less likely to engage in incubation. So we would expect them to have lower productivity. And at the banding sites where we have the most hybrids, we have the lowest productivity.
John Coluccy: Ben, go ahead, John. Yeah, that southern swath too, and you think of the two high states in Ohio with the loss of not only wetland habitats, upwards of 90%, but then also virtually no upland nesting cover anymore. along with what Ben just mentioned with the hybrid and urbanization thing. It's kind of, to me, it's not so surprising that productivity is not very good down there. Yeah, but super, super good stuff.
Mike Brasher: Ben, we've covered a lot of topics here, covered a lot of ground. Help us wrap this up, and then John, I'm going to come to you and ask you to opine a bit about What this means for Ducks Unlimited's work, do we envision using this to kind of modify some of what we're doing, think about different approaches? I asked that question because I'm not as familiar with some of the on the ground programs, where we're targeting, why we're targeting and our current thinking on some of that. So I want your input on sort of does this change anything for us? But Ben, help us kind of wrap this up and tell us what are the key findings and what are the implications from a management standpoint?
Ben Luukkonen: Sure. So under the assumption that we want to continue to maintain or even increase abundance of wild Great Lakes mallards, in terms of population dynamics, what needs to happen is we need to increase female spring and summer survival. So reducing that natural mortality and or increase productivity. Of course, those are probably easier said than done, and we may need some more research to look at what exactly is going to be most effective for doing that. But what our work suggests is that we should be continuing to improve the quantity and quality of the habitat types that are important for nesting and brood rearing. And to be effective, I think we need to affect habitat positively at a regional scale. The other side is our results suggest that reducing hybridization between wild and domestic game farm mallards would also be beneficial in increasing productivity specifically.
Mike Brasher: You know, and one of the things I'll point out here, Ben, is sort of the role of scientists versus some of the managers and decision makers as scientists. And in your case here, you conduct the research, you provide the information or you analyze the information, you summarize the findings. Provide it to the decision makers to act however they feel is appropriate relative to whatever the objectives they have are and those objectives could be any number of things. So the important thing that just want to clarify here is you're not. making recommendations here for management or anything of that nature. You're presenting the information, say, this is what we're learning. These are the potential issues. These are some ideas. But ultimately, it's up to the decision makers in various agencies and entities to use this information. Science doesn't make the decision. Science provides information and understanding of phenomena of nature. It's people that make decisions on what to do with that information. to address our objectives. And I know the states that have helped fund this research are thinking about those things. I don't know the status of any of those discussions, and that's a conversation for a different day. But anyway, I just want to make sure we clarified some of that. So I'll give you a minute to think about any closing comments, Ben. In the meantime, I want to go to John and ask him, from a Ducks Unlimited perspective, how do we use this information and what can you tell us about whether at this time we're thinking about modifying any of the work that we're doing or innovating around other programs to help address some of these issues?
John Coluccy: Yeah, I think really important work and, you know, the joint ventures right in the middle of helping fund this project and ultimately our conservation planning we do through our habitat joint ventures, the Upper Miss Great Lakes joint venture and Ultimately, information like this from Ben's study and many others, we take that best available science and adapt that into guidance for our conservation programs for all the partners that are delivering habitat on behalf of waterfowl and other species in the region. This, ultimately, when we revise that waterfowl conservation strategy, Ben's information will be wrapped up into that. Some of the findings are pretty consistent with some of the work that we did previously with some wrinkles, obviously, but we've always had a pretty big focus on the breeding period with respect to improving conditions for breeding mallards, blue and teal in the region as well. And so, you know, using this information again to kind of maybe reinforce and double down on that the scale thing is a challenge I think Mike and Ben for for our region and trying to implement. you know, wetland and upland conservation. It's not, we've got a very fragmented landscape and so, you know, it's gonna be important for us to focus our efforts, I think, in building complexes associated with existing work that we've done in the past, whether they be anchor points with state wildlife management areas or waterfowl production areas that the U.S. Fish and Wildlife Service operates. National Wildlife Refuges. And so, you know, really focusing in and dialing in on those really important landscapes for breeding mallards. But, you know, we've had a focus on pair ponds, brood-rearing habitat, and a little bit to a lesser degree on nesting cover. But from Ben's work, the CRP graphic is an important one for us to reconsider. And now that we're involved and we're growing and expanding our regional programs into working lands, more ag-focused programs. There may be some good opportunities there for us to work with NRCS and other partners to implement at a broader scale across the landscape and really help drive this. The Great Lakes is a pretty high-priority landscape for us for a couple reasons, for staging and wintering waterfowl, but also breeding waterfowl is a priority for the organization. The one thing that is interesting too is, you know, as we've tried to, through the North American Waterfall Management Plan, try to engage a broader support base, the general public and folks that are interested in recreating and they're interested in seeing waterfowl and get them engaged in wetland conservation and what we do. Our last iteration of our conservation strategy for the Upper Miss Great Lakes Troy Venture included distance from urban areas as a factor in our multi-criteria decision support tool. And now thinking about what's going on with urban mallards and the genetics and things like that, it kind of makes you rethink. It's like, well, is that really doing any good? It's doing good from the people perspective. And so those are the folks that are helping generate the support for the mission, the political support. financial support for our mission and putting Habitat on the ground. So, yeah, but you're thinking of that kind of trade-off there with actual benefits for mallards versus people. So, interesting stuff to consider.
Mike Brasher: John, I'll be honest, I had not thought about that yet, but you're exactly right. It's another Other trade-off to consider? Interesting. And it's a really good reminder that we talk about conservation reserve program and the importance of it mostly, I think, and I'm certainly guilty of this from a prairie pothole region standpoint, for good reason. That's our highest priority landscape. The CRP through the years has had profound impacts on productivity of ducks in that landscape, but this is a great reminder that the Conservation Reserve Program, the vegetation it puts back on the landscape, provides a very important role for supporting breeding ducks in other geographies as well. This being one of those, really cool that we're able to find a relationship between declining productivity and declining acres of CRP on that landscape. I mean, it's cool. It's not good to see, right? And we don't like to see those declines, but as researchers trying to figure out what's driving things that are concerning to us and being able to find some relationships that are sort of strong statistically, but that ecologically make a lot of sense. You can imagine how those mechanisms are operating. That's a rewarding thing to come out of a study like this. And so with that, Ben, I want to throw it to you for any final comments, any epiphanies, any other thank yous that you want to make, but help bring us home here.
Ben Luukkonen: Yeah, I guess just a couple things come to mind. I think in terms of the science and management community, I think we should continue to invest in these long-term monitoring data sets, banding, harvest surveys, and aerial surveys really form the foundation of waterfowl monitoring. And so I think this project helps to show the value of those datasets. And I think it's important to continue investing in those in combination with genetic monitoring, given what we're learning. Secondly, I think the public and hunters in particular should think about Is it important to continue to maintain the social, ecological, and economic benefits of wild mallards and think about what we're learning? And if that's a concern, make your voice known. And then lastly, I just want to say a big thank you to Ducks Unlimited and the rest of the partners for their great support on this research. We couldn't have done it without their help.
Mike Brasher: Thank you, Ben. I guess a final question I would pose, if you're able to share, I don't know how public any of your next plans are, but are you able to tell us where you're going next?
Ben Luukkonen: I am. Yep. I just got married and moving across the country to start a new job as a waterfowl biologist with the Coeur d'Alene tribe in Idaho. So I'm excited about that, excited to experience the Pacific Flyway, but I hope to stay involved in this Great Lakes Mallard issue as well.
Mike Brasher: We're in this profession because we're obsessive and crazy about the animals for one reason or another. But this story is another example of why it's about way more than that. It's about the people. It's about the relationships that we make. It's about family relationships, helping us figure out who we want to be in our lives as adults. And Ben, I certainly know that's the case for you. It has been for John and me as well. uh and kind of navigating this career path and and so it's really cool to have followed you on that path and um and to help support your work and your professional and personal development and look forward to working with you now and in various ways um on on important issues related to waterfowl wetlands and other parts of the country so thanks so much guys this has been a great conversation an incredibly important topic, a range of topics, and helping us do more and do better for waterfowl populations all across the country. So thank you, fellas. Appreciate it, Mike. Yeah, thanks so much. A very special thanks to our guest on today's episode, Dr. Ben Luukkonen, recently graduated from Michigan State University. Appreciate all the hard work that he's put into this great project. Dr. John Colusi, Ducks Unlimited's Director of Conservation Planning and Science for our Great Lakes and Atlantic region. We appreciate him making his debut on the Ducks Unlimited podcast today. We've enjoyed the conversation with him. Thank my producer, our producer, Chris Isaac, for the great job he does with these episodes, getting them out to our listeners. And we thank our listeners for your time and support of wetlands and waterfowl conservation. And we'll catch you on the next episode.