DU Podcast Transcript: Ep. 19 – DU Chief Scientist Discusses Last Season’s Question “Where were the ducks?” (1 of 3)

Dr. Tom Moorman talks weather, hunting, pressure, habitat

© Michael Furtman

Clay Baird: Welcome to the Ducks Unlimited Podcast, the only podcast about all things waterfowl. From hunting insights to science-based discussions about ducks, geese and issues affecting waterfowl and wetlands conservation in North America. We bring the resource to you. The DU podcast with your host, Chris Jennings.

Chris Jennings: Today we're going to talk about a very, very important topic. Something that was on the top of everybody's mind last season I know, and probably continuing through the summer, is the difficult duck season that we all had. Some of the questions that we had. The main question that I probably heard over and over and over again was, where are the ducks? And today I've got Dr. Tom Moorman, DU's Chief Scientist to come in and walk us through the many, many variables that come into waterfowl migration. Why waterfowl migrate, reasons for them to stick around, things like that. Tom, welcome to the show.

Tom Moorman: Thanks Chris. Glad to be here.

Chris Jennings: Awesome. Awesome. The first thing we're going to talk about is, is the one that everybody already knows about, weather. And you've brought it up before, we've all talked about it. Duck owners will look at their phones nonstop to see the weather. Where's the next cold front coming in? Where's the next ... What did they call it? The polar vortex that's going to be pushing ducks. That's what we're all paying attention to, and kind of get into the reasons why waterfowl really migrate.

Tom Moorman: Sure. It's pretty intuitive. The winter weather drives migration to a certain extent, and it's those big cold fronts that produce lots of snow or behind them freezing air comes in and freezes up wetlands, that push birds to the point I'm making a decision to stay or go. That decision is in part heavily influenced by their access to food resources. So, if they're buried by snow or covered in ice, they can hang out. For instance, a mallard could stay upwards to seven days and survive on fat reserves, if it's a really healthy bird. But the challenge for the bird or the sort of the risk tradeoff is, if he stays longer and it stays cold and frozen and he stays too long, then he can't migrate, he's got a problem.

Chris Jennings: Yeah. He's really gambling there.

Tom Moorman: And so they balance the risk, and typically we'll see them make a move and it's not instant. Usually we see them moving two to four days after heavy snow fall or onset of winter wheather in Northern latitudes, that bumps them. And-

Chris Jennings: Now what did you said, with the snowfall? Is there a set depth of snow that ... It's been recorded to say Canada geese will leave when it's 12 inches of snow or?

Tom Moorman: Yeah, there's not any science that says-

Chris Jennings: okay.

Tom Moorman: ... what depth. It's really if you just sort of contemplate the burning questions. Canada geese for instance, especially giant Canada's, are big enough to root around in say six inches of snow. They could make a go of it if they had to. Mallards, not so much.

Chris Jennings: Yeah.

Tom Moorman: Two, three inches, they may can poke through that and forage around. But if it gets beyond that, it's hitting them. You can picture them walking around in a field-

Chris Jennings: Oh, yeah.

Tom Moorman: ... and they've got three or four inches of clearance and that's about it. So they'd have to bolt.

Tom Moorman: So anyway, I think what a lot of people underestimate about ducks and duck hunters in particular is just how well adapted they are to not only weather, but the variation in habitat that is caused by weather. And that could be rainfall, snowfall or lack of rainfall and snowfall. And why is that the big driver? Well, food is part of the equation, but it's not the only equation. For some species of ducks, especially the early-nesting species, mallards, pintails in particular. They stay as far north as they can, and the reason they stay as far north as they can is because it's advantageous for them to be as close to their breeding areas as possible.

Tom Moorman: So when spring rolls around, they can make the jump and get there. As soon as ice is out, those early-nesting birds tend to be more successful nesters. They have access to the best territories. And remember, all these birds are going to arrive on the prairies and they sort of have to duke it out for territories. A pair of mallards, two pairs of mallards don't occupy the same wetland in the same territory. The dominant pair will chase the other pair out of there. So there's a real advantage to get in there first. And for that female, they tend to be the older birds, the more successful birds, and have a higher probability of raising a brood to flight stage. So there's a real biological advantage to stay in as far north as you can just to be able to respond to the onset of spring conditions in a really time-sensitive conduit.

Chris Jennings: Yeah.

Tom Moorman: So we see some of that. And then I have, sometimes people will say, well, there are other ducks who don't do that, and that's true. And we'll use a blue-winged teal for instance. Part of this gets a little complicated too because it ties to foraging ecology. Blue-winged teal, shovelers and gadwalls especially, are what I would call wetland obligate feeders. They don't feed typically in uplands, so they have to feed in wetlands. Blue-winged diets are comprised heavily of invertebrates with some seeds, shovelers mostly invertebrates, and gadwalls, mostly submerged aquatic vegetation. If ice covers those, they got a problem.

Chris Jennings: Yeah, they're out.

Tom Moorman: And so, for blue-winged, sometimes even as early as August. And for the other two, September, October. They really have to hedge and they really have to go with the onset of some what I would call cool fronts that signal things are changing, and they got to go.

Chris Jennings: Yeah, they can't just jump into a cornfield and feed.

Tom Moorman: They typically do not.

Chris Jennings: They have to get ... Okay.

Tom Moorman: There's no records of which I'm aware of for those three species to be field-feeding.

Chris Jennings: Yeah, absolutely.

Clay Baird: [ADVERTISEMENT]. Be the first to know when ducks are on the move. Sign up for DU's waterfowl migration email alerts and receive ongoing in-depth updates on the latest habitat conditions, weather changes and hunting reports for your flyaway. Visit ducks.org/migrationalerts.

Chris Jennings: One of the things that you've mentioned here is their reason to stay, and that's very important. And it's also been mentioned, like their mortality. I know you talked about the one, it's of better habitats, things like that. The mortality, is that something that plays into because of the longer flights, or is it ... How does that play into this reason to stay?

Tom Moorman: So birds, all migratory birds have some risk mitigation and that's sort of the human or anthropocentric way to think about it. Basically, migration is a trade-off. You can stay and minimize your risk of exposure to things like predation, including hunters, or risk of not finding quality habitat, or hitting a drought area in the Mississippi Valley or something like that.

Tom Moorman: Or, you balance that against, I got to go because it's going to freeze. And so there's a trade-off there for them. On one hand, they want to stay as far north as they can, but they do have to have access to food, replenish daily energy requirements. And so they can't hang out through extreme winter. And the signal there is freezing up of wetlands and snow cover, but they still only need to go so far as to find some open water and some food.

Chris Jennings: Okay. Yeah. And that's one thing I've talked to people who ... One of our freelance contributors mentions, he's from South Dakota, and he mentions on the Missouri River, they'll have a quarter of a million mallards in January.

Tom Moorman: Yeah.

Chris Jennings: And they're tucked in, as long as there's any open water on the Missouri River, they'll hang out there.

Tom Moorman: Yeah. If they get open water, and of course that part of the world is heavily in agricultural production, especially corn. Harvested corn up there, typically there's waste grain on the field and if those mallards can make access to that and it's not buried in say six, eight inches of snow, yeah, they'll hang. They're tough birds.

Chris Jennings: Yeah. I was going to say, they are tough, really. Give them the respect they deserve, for sure. And you also mentioned some things, some of the science that's pointing towards the potential for mid-latitude states continuing to have a little bit warmer winters. Kind of explained that, and what waterfowl owners should expect?

Tom Moorman: Yeah. This is a topic that is garnering more and more interest in waterfowl management community. And in part, it's because hunters have questions, "Where are my ducks?" And on an annual basis weather is influential, is one of the main influential features of whether or not you're going to see birds at wherever your latitude is. If you get the weather that pushes migration, then you'll see birds and if you don't you won't. So that's annual variation.

Tom Moorman: What we're kind of interested now though are a lot of researchers are starting to look at, as to whether there had been longer term trends in non-breeding distribution where we're starting to see the center of the concentration of something like mallards shifting north. And why would we see that if we did, and it all hinges on warmer winters. There are a couple of papers. One model's actually downscales climate models and looks at both shorebird and mallards and pintail, a non-breeding distribution in winter. And predicts that within 40 to seven years that mallards may winter as far north as Nebraska.

Tom Moorman: Now, when we just talked about some birds that sit on the Missouri River, we're not talking about that. In some years up to a couple hundred thousand is in there, we're talking about the center or the core of the population shifting. That would be something of significant concern to the entire waterfowl management enterprise if that happens. Because obviously, mallards are really critical to all hunters, and particularly as you move south in latitude, places like Arkansas, they're known for their classic Mallard hunt.

Tom Moorman: So this is a model, it's done by some USGS scientists, the names of Gordon Reese and Susan Skagen...

Chris Jennings: Okay.

Tom Moorman: ... out there in Colorado. That particular study was a model done on the playa lakes country and the panhandle of Texas. And they down-scaled the climate models and sort of did that whole playa lakes on up into Nebraska scenario. And what they detect is, or what the models predicts, is that mallards will shift north. And if you're a Texas panhandle hunter, the good news is, pintails shifted north off the Gulf Coast. But if you're a Gulf Coast hunter, the news would not be as as bright there.

Chris Jennings: Yeah.

Tom Moorman: So this climate change and warming winters is definitely an issue. Dr. Mike Schumer, who maybe we can have on future podcasts, he's investigated this quite a bit. He has a weather severity index. And he and his team at State University of New York, cooperating with some climate scientists at the University of Wisconsin, has some additional models that suggest similar things. And in that particular study, the suggestion is that migration will still happen, but it will be delayed.

Tom Moorman: And so when you might typically expect, if say you're a, I don't know, an Arkansas duck hunter, we get a little influx of birds late October, early November. But the brunt of birds start to arrive late November and into December. What that model projects or predicts is that it would be later into December, maybe even early January for something like a mallard to have to be moved out of the, say the Great Lakes region or the Midwest.

Chris Jennings: Yeah.

Tom Moorman: So some interesting things to think about. And of course our job is to kind of figure out what that means from a conservation planning standpoint. Does it mean anything in the near term?

Chris Jennings: Yeah. But that would put a strain on the wintering habitat in those areas where they're shifting to because-

Tom Moorman: Well, that's what Dr. Schumer's, one of his points in his research is, that there is not at this point sufficient habitat developed or managed to support an increased population of wintering ducks.

Chris Jennings: Yeah.

Tom Moorman: And so that has implications up there and it sort of tears down from there. But yeah, it's a, I would say an emerging area of science and research in waterfowl and we just have to see what the climate data show. The National Climate Data Center has a lot of good information online. Some of the things I look at, even on an annual basis, I look at ice cover in the Great Lakes.

Chris Jennings: Yeah, absolutely.

Tom Moorman: Snow cover model, they have both of those on their website. You can look at snow cover in almost real time, a day later.

Chris Jennings: Yeah.

Tom Moorman: So that big storm that hit Manitoba and Dakota's earlier, week or two ago, you could of go the day before and there would have been no snow and you could look two days later, and there had been in some cases two feet.

Chris Jennings: Wow.

Tom Moorman: And you could detect that.

Chris Jennings: Yeah.

Tom Moorman: And of course that has implications for bird movement.

Chris Jennings: Absolutely. Absolutely. And I know, personally I'm constantly checking my app, just to see where the snow is, where the snow .... I mean, most of the, even the most basic apps, provide a snow cover model.

Tom Moorman: Yeah. I'm old enough to remember a time before iPhones and apps. So, what you did then was turned on the Weather Channel and watched it constantly.

Chris Jennings: Yeah. You had to watch it all day.

Chris Jennings: Well, hey, we'll go ahead and wrap this podcast up, this one was all focused on whether. We're going to get into several different variables as far as migration and wintering distribution here. Thanks, Tom.

Tom Moorman: You bet.

Chris Jennings: Appreciate it.

Chris Jennings: Special thanks to Dr. Tom Moorman, our guest today, and a special thanks to Clay Baird, Ducks Unlimited podcast producer, who does a great job putting this show together. I'm your host Chris Jennings. Thanks for joining us and thanks for supporting wellness conservation.

Clay Baird: Thank you for listening to this episode of the DU Podcast. Be sure to rate, review and subscribe to the show and visit www.ducks.org/dupodcast for resources based on today's topics, as well as access to more episodes. Opinions expressed by guests, do not necessarily reflect those of Ducks Unlimited. Until next time, stay tuned to the ducks.