DU Podcast Transcript: Ep. 24 – Introducing a Science-Based Approach to Duck Migration Forecast (Part 1 of 2)

Host Dr. Mike Brasher brings in Dr. Mike Schummer to explain his current project of a weekly duck migration forecast

© 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, Dr. Mike Brasher.

Mike Brasher: As hunters and birdwatchers well know, weather has a large influence of waterfowl migration, but the details of this relationship remain heavily discussed and debated. Today, we welcome Dr. Mike Schummer, a leading authority in this field, to help us understand. Dr Schummer is the Roosevelt Waterfowl Ecologist at the State University of New York College of Environmental Science and Forestry. Mike, welcome into the show.

Mike Schummer: Thanks, Mike. Really appreciate the opportunities to talk to folks.

Mike Brasher: Yeah, it's great to have you, so I want to start out by giving you an opportunity to talk a little bit about your background, your personal path, your professional career and where you are now, and how you became interested in this topic. I know you've described yourself as sort of a closet meteorologist, I think you're more than that at this point, so go ahead and tell us a little bit about yourself and your work.

Mike Schummer: Yeah, thanks. Like all these professional development things, it's been a long journey, and a lot of it comes from growing up in a very rural community in western New York, in a hunting and fishing and farming kind of family. Just really kept with that theme, throughout much of my life as a duck hunter, as a scientist, and as an educator. My background is really in forestry for my undergraduate degree, then I went on to do some school in Missouri, which was a wildlife degree, and then my doctorate in Ontario in Canada. So done a bit of traveling on that end of things, and as most waterfowl biologists, I think, should to understand birds at both ends of the spectrum from breeding, through migration, and then on their wintering areas. That's what really got me pretty keen on duck migration, is just trying to understand what the underlying mechanisms of that were, both just from a science standpoint, but also personally as a hunter. I think people check their phones two, three times a day during duck season, it's a really common thing, and I just wanted to put some science to it.

Mike Brasher: Yeah. Well, before we had our phones, we were camped out in front of the TV at five o'clock or six o'clock every night to see what those graphics were going to show on the... to see where that cold front was going to be draped across the continent. That's what we used to do.

Mike Schummer: Yeah, and that's changed. The technology now is amazing. What I have at my fingertips to work with is far beyond what we had just 20 years ago. I think that's what makes it interesting, is that we're starting to be able to tease apart some of these relationships between birds and the weather.

Mike Brasher: Yeah. Well, before we get into some of those details, maybe just... have you been able to get out and start hunting yet?

Mike Schummer: We had a pretty slow start to our season here in central New York, is where we're located now. For folks that aren't familiar with this part of the world, we're just south of Ontario and Quebec, so as birds make their first movements, they pile up on us pretty quickly. It's a hidden gem really for water fowling. We hunt birds from the 1st of September pretty much right through till about the first week of January because we've got a lot of deepwater habitat and such, and various [inaudible 00:03:51].

Mike Schummer: We had a really late spring. I think we had a lot of failed nesting attempts early on, and we were catching ducklings that we couldn't even put bands on in the Adirondacks mid-August. So I think there were a lot of birds that took a while to mature and... because a lot of these ducks, when they get big enough to fly, the first initial movements aren't always about the weather, they'll move based on... they're just not going to stay in Canada. They're not going to stay in the Ottawa River Valley, so they make those movements. So we get a bunch of these hatch year birds, young birds, that show up August, September, but we didn't really get that this year.

Mike Schummer: We had early migrants. I've been getting into wigeon, gadwall, more green-winged teal than normal. Our mallard limit in the east is at two birds and not four, and that's hurt me on several occasions where I come out with four ducks or five ducks. I'm usually getting my two mallards each time, but then just not filling the bag out otherwise. But it's been good, it's been good. We've gotten out a bunch, the dogs have gotten some running. You can't complain.

Mike Brasher: Yeah, that's a good thing. Our season has not opened yet, so I'm looking forward to that and looking forward to getting back to some of the places I grew up hunting, now I'm in Memphis and little bit closer to where I grew up. So I really am looking forward to that this year, especially since I missed all of last duck season with a little health issue. Anyway, I'm beyond that now, so let's talk a little bit about weather.

Mike Brasher: Invariably, you and I have found ourselves in conversations with duck hunters or duck biologist, and we talk about these weather variables and how it's going to get cold or it's going to snow, and we can anticipate bird movements in response to that. A lot of times, I've found myself in those conversations and we're only talking about one variable. It's like, "Well, what's the effect of this temperature?" and, "What's the effect of snow?" What we're going to talk about here is an index that you and colleagues developed called a Weather Severity Index.

Mike Brasher: What I find so valuable about this index is you were actually able to, I think, quantify what we suspected, and maybe what some early researchers had opined, that it's not any single meteorological variable, it's the combination of these variables that are really going to have an impact on what moves birds. The ability to quantify that is really, really fascinating because it opens a tremendous number of doors. So tell us a little bit. Take us back to, I guess it would have been, I know the publication came out in 2010, but take us back to the late 2000s when you were at Mississippi State working on this idea, and sort of walk us through, briefly, what you all did and what you came up with.

Mike Schummer: This was a really fun project. It developed organically. This was when I was, as you noted, working at Mississippi State with Rick Kaminski. We just started to talk about potential projects that were of interest to waterfowl hunters, waterfowl and wetland conservationists and managers, and this one really boiled to the top right away. I had always had a strong interest in and was kind of an armchair meteorologist, and strong interest in weather. Rick sent me off and said, "Well, go work up some numbers." We had to get the waterfowl survey data first of all, so we worked with Missouri Department of Conservation, who has some really solid aerial and ground survey for over the years, and then selected weather stations that were near those conservation areas, and started to look at are the combinations of different types of temperature, snow cover and wind direction. We looked at moon phases, we did sunspots, we looked at a whole gamut of things that didn't end up anywhere near predicting duck migration.

Mike Schummer: What's neat about it is it came out to be this combined effect of temperature and snow that was really doing the best job of predicting the birds' movements, and that makes sense. We were really focused on mallards mostly, and a lot of that was... Rick had written an article that said, "Where have all the mallards gone?" A popular article. Right before I got there were a few years that the hunters were seeing either birds weren't showing up until late or there just weren't many of them despite that those birds did exist somewhere on the continent.

Mike Brasher: Yeah. So Mike, remind me specifically of the variables that feed into this, because it's not just temperature on a given day, it measures cumulative days of some degree, right?

Mike Schummer: Yeah. It is the temperature on that day, so there's the direct effects of weather on a bird on that day for its to either stay at a location or migrate. So it's how cold it is on that day, how many days in a row it's been below freezing, how much snow is on the ground that would interfere with, say, field feeding and things like that for field-feeding mallards, and then how many days in a row has there been measurable snow on the ground? This all makes sense because you have this effect of the cost of just existing in a place that's cold and snowy, and then the capacity to actually acquire food to really maintain your body temperature. So the cumulative temperature effect is the icing effect of wetlands, the cumulative snow obviously just makes it more difficult for birds to find grains in fields. This is a little in the weeds, but we have one number that explains close to 50% of the variation in changes in duck abundance between any two days with a single number, which given all the other variables that are out there is astonishingly good.

Mike Brasher: Well, that's right. In a natural system, if you can explain 50% of the variation in some phenomenon that you're observing, you've found something.

Mike Schummer: Yeah.

Mike Brasher: Okay. We've got the Weather Severity Index calculated here. The next thing was to apply to sort of a forecasting, if you will. You were able to do the work, you linked this to the observed change in duck numbers, and so now you want to take this forward and see if we can make some projections about what we might expect during a forthcoming week based on weather forecast. Explain to us what you all did in that regard.

Mike Schummer: This is the part I really like. This isn't all just high science and stuff, this was just interest by myself. With an increasingly busier schedule, what days could I go when there was a greatest likelihood of bird migration? So, we find this relationship, and after this threshold of severity of weather, we start to see declines in birds at a given location, and the greater that Weather Severity Index or WSI becomes, the greater number of birds will be leaving that location between two dates.

Mike Schummer: That's really how we apply it at the high-level scale is, are birds not even making any movements? Then, there's a period when there's peak increases in ducks at a location, and those get scored as... we color code it for what's online now, and then everything after that is decreasing numbers of birds. That's the easiest way to do it, to express it to folks because it depends. If you're at a location that's holding 250,000 mallards, for instance, compared to a place that's holding 1000, you're going to have a lot bigger movement of birds, obviously, out of that one that had, say, 250,000 birds. So it basically is relativized, saying that this much change in abundance is going to happen between two times.

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 flyway. Visit ducks.org/migrationalerts.

Mike Brasher: The other thing that you've done now, and you briefly referenced this, Mike, is you've taken those relationships and you calculate or you generate weekly migration forecast for the Mississippi and Atlantic Flyways based on forecasted weather, matching this Weather Severity Index, across a number of locations in the northern and mid-latitudes of basically eastern North American. We're going to get into that on a subsequent podcast, we're going to have you back to talk about one of those weeks in particular, just to give folks some exposure to that and how it works, if you will. So, thanks for that explanation.

Mike Brasher: What I want to do also is go back a little bit to one of the variables that you tested in your original Weather Severity Index analysis, it's also featured many times in conversations with people when talking about what causes birds to move, and that's photoperiod. I went back to your original article this morning as I was preparing for this and reminding myself that you in fact did include photoperiod among the variables you looked at. I know I might be catching you off the cuff here on this, but do you remember how that fell out?

Mike Schummer: Yeah. It did not do as good of a job at explaining the movement of birds as weather, but the details on this are important. As photoperiod gets shorter, as we move towards December, our weather is also generally getting worse, more severe. So it's not that photoperiod doesn't cause birds to make movements, it's just that, in addition, the effects of weather do a better job of explaining migration. So in no way are we saying that it's not affected by photoperiod. In fact, if we go back to when you asked about my hunting season and talking about these initial bird movements, when they're leaving those breeding ground areas, those are photoperiod cues. That's called a fixed migration. Then, thereafter, the weather and the accumulation of severe weather, once they're at these first staging areas, and in the Atlantic Flyway a lot of these birds move into the Great Lakes region and hang out in those marshes until the weather becomes severe enough and then move. So, some of those initial movements are photoperiod based, or how many daylight hours there are, but then later on they become increasingly flexible, and that's really affected by the weather.

Mike Brasher: Species differ a little bit in their responsiveness to photoperiod as a stimuli for migration, right?

Mike Schummer: Yeah, they do. The one that when we expanded this beyond mallards, and we had a graduate student at Western University in Ontario work across all of the dabbling duck species, she found that what best explained blue-winged teal migration was photoperiod, which makes perfect sense because they act like a neotropical migrant, they act like a scarlet tanager or something that is not going to stay in its breeding area, and it's going to a very stable environment in the tropics and subtropics. So, once it's done its thing and it's in condition, it just goes, and it's very photoperiod based. Now, saying that, there must be some flexibility in it still because it does seem like we're getting more and more reports of blue-winged teal staying late, and especially along the coastal areas. Louisiana folks are talking a lot about blue-wings that are hanging around quite a long time. So even they have some flexibility.

Mike Brasher: Yeah. A perfect transition to where I wanted to go next, you referenced the fact that... We started with mallards, this severity index began with mallards, and then you collaborated with some additional researchers to develop this index for... was it six additional species? Do I have that right?

Mike Schummer: It's for mallards, black ducks, which essentially are pretty much the same model, they react very similarly, gadwall, wigeon, green-wing teal, and-

Mike Brasher: Shovelers.

Mike Schummer: Shovelers. We did blue-winged teal, but the weather isn't really the predictor, so we don't even do anything with them. There's dates that seem to be just kind of fixed dates which have the greatest likelihood they would migrate.

Mike Brasher: No divers so far in this analysis, right?

Mike Schummer: No. We'd like to really move into geese and diving ducks. I think we're going to have the opportunity to do that in the near future. It's literally about bodies data and funding to run graduate students through, the methodology is pretty much there. So we haven't touched divers yet. The one that everybody talks about is that first full moon in October, the scaup move on, and that one is consistent. Boy, it's really, really consistent, and then, thereafter, they seem to trickle down the flyway afterwards. So that's going to be an interesting one to get into working with moon phases, I think, with diving ducks because I think there may be some real relationship there.

Mike Brasher: Yeah. Well, my kudos to you and your colleagues for taking this conversation that we've all been part of so many times and putting numbers to it. Putting numbers to it allows us to do so many things going forward, and I want to give you an opportunity to reference this briefly. As you and I discussed before we came on the podcast, we don't want to go into too many details on this because we want to save time to bring you back and discuss each of these items in more detail. But this is more than just academic, the development of this index, because it allows us to think about how changes, if you will, in migration phenology may impact our conservation planning. It may impact our efforts to recruit hunters and supporters of waterfowl and wetlands conservation. So I'll give you a few minutes here to talk about, just briefly, the importance of this to those items.

Mike Schummer: Yeah. I think that's really where the rubber hits the road on this, is how do we translate this into information that's usable for waterfowl and wetlands conservation, immediately and into the future?[ For instance, on our really mild years, we have up to two million ducks that we estimate are able to stay at mid-latitude locations, that don't have to go to southern latitudes, and southern waterfowl hunters have seen those painful years. That's two million birds that you need to feed. We figure how much energy each one of those animals needs, and we can get to the point where we understand how many acres are actually needed to feed those animals. Then, on the real severe years when the millions of birds move south, we need to make sure that we have those acres on the ground, too, so understanding the distribution... These are pretty good-sized animals, there's lots of them, they have high energy needs, and they feed from deepwater areas to terrestrial habitat, so they have a real impact on their environment, and the habitat we put on the ground has a real strong impact on them. So I think that's the most useful tool, is understanding where these birds are going to be and when.

Mike Brasher: Having spent the first 13 years of my career as someone who was responsible for conservation planning in cooperation with a lot of partners along the Gulf Coast, we used these models to sort of project where we thought birds were going to be or how many birds we thought we would have in our planning region, and we treated them as sort of static numbers. We knew that number varied from year to year, but our conservation planning was based on some sort of static treatment of those objectives. So the information that you've developed, the models you've developed, give us a numerical way to start thinking about that, and that's pretty exciting from a conservation planning standpoint.

Mike Brasher: The other thing that you've done with this, we've referenced a couple of times and that will be of probably immediate interest to hunters on an annual basis, on a weekly basis, within our hunting seasons, is you have a weekly migration forecast for the Mississippi and Atlantic Flyways, basically the eastern North America, eastern US. Where can people find out more information about the work you've done and this forecasts?

Mike Schummer: The easiest way to find it without me spelling out what the webpage is, is if you just type Schummer, that's S-C-H-U-M-M-E-R, two Ms, and so Schummer duck migration, in Google, it's the second page that comes up. It's right under the Ducks Unlimited migration forecast on Google, and it'll show right up there.

Mike Brasher: Thanks so much, Mike, for your time. Thanks so much for the science that you brought to this conversation.

Mike Schummer: Thank you very much.

Mike Brasher: Thanks again to our guest today, Dr. Mike Schummer. We look forward to having him back on the podcast. I also want to thank our producer, Clay Baird, and thanks to each of you for supporting Ducks Unlimited.

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.