DU Podcast Transcript: Ep. 42 – Do Ducks and Geese Mate for Life?

Hosts Chris Jennings and Dr. Mike Brasher discuss waterfowl mating systems and how behavior changes related to mating and courtship directly impact hunting as the season progresses.

© 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 and Dr. Mike Brasher.

Chris Jennings: All right. Today's topic is one that has stemmed from really consistent questions that I've had come through the website, on social media, even just random people that know and that I talk to say, "Oh yeah, you work for Ducks Unlimited" and they'll shoot this question. And so I've got my cohost, Dr. Mike Brasher here to answer all of these super scientific questions. And the main question is, do ducks and geese mate for life?

Mike Brasher: The answer is no and yes.

Chris Jennings: Now it's clear.

Mike Brasher: The answer is never no and yes in question of nature. We'll start there.

Chris Jennings: All right.

Mike Brasher: But mating systems waterfowl is a incredibly fascinating topic to me. I was actually able to study it a little bit with my master's research. We're investigating the social behaviors of paired and unpaired male mallards during the breeding season. I think we had an earlier episode on that, but it exposed me to a little bit of the mating systems of waterfowl. And this is something that occasionally if you go back through the DU magazine archives, you will find some articles about this, I've written one.

Mike Brasher: Generally what we see in waterfowl, and I have to say generally because the moment you start saying one, you lay out some situation the way it is, you can immediately find an exception to that. And that's what makes this really fascinating to understand and explain why these differences may occur. At the most basic level, and let's just talk about North American species for right now, ducks are what we refer to as seasonally monogamous. That means that it's one male and one female monogamous. But the seasonal aspect means that those pair bonds are intact for only about six to eight months a year. And it varies among species, the link of those pair bonds and the timing of when they initiate, but so-

Chris Jennings: And you're saying like six to eight months is probably a mallard?

Mike Brasher: Yeah, probably closer to eight months on a mallard. I would say there's some of the earlier-

Chris Jennings: I'm just trying to give people a broad-

Mike Brasher: Yeah, yeah.

Chris Jennings: It's going to be different for every species.

Mike Brasher: Right, so by and large for ducks, we're talking seasonal monogamy, one male, one female, those pair bonds are in place for only six to eight months a year. Those pair bonds break and in most duck species, they don't re-pair with the same mate the following year. Now we can contrast this pretty starkly with geese and swans, and even Black-bellied Whistling ducks, which are bigger in body size. There's a relationship there, what they do, they are what's known as perennially monogamous. They're monogamous, one male, one female, and the perennial aspect means that they mate for life. So geese and swans, and whistling ducks mate for life. Ducks in North America, it's one male, one female, but those pairs break every year with some exceptions.

Mike Brasher: There are some species notably in some of the goldeneye, some of the sea ducks, believe it's harlequin ducks or long-tail ducks, there are some fairly well documented cases of the same male and female pairing back with one another the following year. And so basically what happens, let's just sort of play this out as we go through a typical fall and winter period, and let's talk about ducks because geese and swans aren't all that exciting from a dynamic mating system perspective because it's the same male-female year round.

Chris Jennings: Yeah.

Mike Brasher: For a duck, this time of year, we're recording this in early December, some duck species, mallards, pintails, black ducks, and gadwall even, are actively in the courtship phase. They've completed their molt. They're now in their bright breeding plumage or if not, they're nearly so. There's a lot of courtship going on out there. The males are trying to pair up with the females, and so those pair bonds will develop and those pair bonds will continue into the spring. The males will follow the females back to the breeding grounds. The females are the ones that are more what we call philopatric, means they go back to their natal breeding site more so than the males.

Chris Jennings: So the males are just following the females around.

Mike Brasher: The males are just following the females around. And here's a little slight deviation from the stories. Ducks are really unique in this regard from a lot of other bird species. In a lot of your songbirds, it's the males that are philopatric to the breeding sites. The males go back first in these little songbirds, they go back first, establish territories, and then they defend those territories. They're trying to select territories that are of high quality and in food resources, breeding sites and so forth. And so then the females go back, migrate separately from the males. Again, we're talking songbirds here, and the males try to attract the females to their breeding sites.

Mike Brasher: Ducks are different in that respect in that the females are the ones that are philopatric. That plays a role in the mating systems of ducks. So anyway, we're back to the progression through the winter. They go back north to the females breeding site. The male generally defends, male ducks display some sort of loose territoriality where they defend an area around the female. They're not necessarily vigorously defending the habitat where the female is. And there's variation here too, so we don't need to get into all those specifics, but as the female proceeds into incubation, starts laying her eggs and completes the clutch of egg, it's around the time when she lays that last egg and begins to incubate that their pair bond begins to weaken. And the male will gradually start to wander a little bit farther from where that female is.

Mike Brasher: Now he doesn't completely abandon her, typically. Again, just speaking generally, he doesn't typically abandon her immediately upon laying that final egg. He's sort of balancing his interest. He wants to stay close enough to that female such that if she loses that nest to predation, or weather, flooding, whatever the case may be, chances are she's going to try to re-nest. He wants to be there close enough so that he can be that-

Chris Jennings: That's why he's sticking around.

Mike Brasher: Right. One of the other things that you see, as the females are laying their eggs, whenever they're laying their eggs, they go to the nest and they lay the egg in the morning typically, and then they're there for a few hours and then they're off the nest for the rest of the day. They go back and hang out with that male, so they're maintaining that pair bond.

Mike Brasher: Then once she lays that final egg, begins to incubate, she's on the nest majority of the day from that point forward, the male begins to sort of pursue other opportunities. The longer into incubation she goes, the weaker that pair bond gets. And he eventually gets to a point where he might try what's called an extra pair copulation. He may try to find another female. The other female could participate in that willingly, but more commonly it's something called forced copulation, which also can be called rape and it can be very unpleasant for the female, and in some extreme cases it can actually lead to the death of the female. You see a lot of these males whose females are off in-

Chris Jennings: That's kind of a situation where you see four or five males-

Mike Brasher: Chasing, vigorously chasing a female and driving her and sort of corralling her to the ground. It's not a pleasant thing.

Chris Jennings: Yeah. Nature's not always nice.

Mike Brasher: It's not, but the extra pair paternity is one of the things that that's called when you have young or eggs in the nest that are fathered by different males, that's fairly common in ducks. Certainly in northern hemisphere. You see that a little bit. You see this extra pair copulation a little bit in geese, but not so much if you think about it, because the male is there with the female all through incubation. The male actually helps with the parental care, provides parental care for the goslings.

Mike Brasher: And one of the other questions that I often times get is why don't the male ducks help care for the ducklings? The simplest way to kind of work that through your mind is to think about, well what can a male duck really do?

Mike Brasher: Like, you go up and try to approach a brood of goslings, and the male and female to that. I mean those are big birds. They can beat the crap out of you. So their presence can actually be very effective at preserving their investment-

Chris Jennings: They can defend the nest.

Mike Brasher: ... in the goslings, right.

Chris Jennings: Where a duck, it doesn't really... Their best chance is to stay hidden, not be seen type approach. Not the male, but the female rather than have the male stand out front like a big Canada goose.

Mike Brasher: That's right. And male ducks in general, and there are some exceptions in general in Northern Northern hemisphere here are, they're brightly colored. They attract attention to themselves, and that's exactly what the female doesn't want. And the male is not very effective at warding off predators for brood or for the nesting hen. So there's not a whole lot to be gained by that, and it's not as simple as that because a lot of other factors influence that.

Mike Brasher: There are some ducks that are perennially monogamous, like swans, geese, not in North America, but in some extreme cases they're highly specialized ducks like usually associated with very limited habitats, like stream dwelling ducks are the best example where you can actually have some. Torrent ducks and blue duck, African black duck, I think they actually do pair for life. The other thing that-

Chris Jennings: Now, let me clarify this because-

Mike Brasher: It's a lot to unpack here.

Chris Jennings: So when you say pair for life, so we're saying geese pair for life.

Mike Brasher: Yeah.

Chris Jennings: What happens when a fox eats that goose?

Mike Brasher: Good question.

Chris Jennings: So does the male, like let's say the fox eats the male. Does that female goose just wander around aimlessly and never raise another brood again?

Mike Brasher: No. There are instances of mate loss, ducks and geese, swans. It happens due to harvest, it happens due to natural mortality as you described. And in in nearly all of the... I can't say nearly all the cases, but basically it's readily documented that those individuals will repair. The bird's not going to be so heartbroken that it goes through the rest of his life unpaired. Now there are some consequences to mate loss. There's been some work, I believe it was Brant that showed, I can't remember if it was a female, maybe it was the females whose male mate was shot. They repaired sometimes rather quickly, but they suffered reduced survival as a consequence of that. Presumably because of the additional costs associated with the process of repairing. Because they're being courted and chased and having find a male and all. They can't just pull out the Tinder app and just do whatever they do there.

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Mike Brasher: For ducks, when we talk about mate loss, this is another area. A lot of times you think about mating systems, what in the world does this have to do with waterfowl conservation, waterfowl management? Actually has a lot to do with it. When you start talking about the consequences of mate loss as result from harvest. That's one of the reasons why frameworks don't get... probably the primary reason why frameworks right now don't go any farther than the end of January, is because when you start going into February, there's a cost. There's a real cost to those females losing that male mate into February because they want to get back to the breeding ground as soon as they can, initiate that nest as soon as they can, because early nesting is consistently correlated with higher productivity, which relates to persistence of wetlands throughout the summer. The later you go, the more likely it is that the wetlands are going to dry out, and your brood's going be left high and dry. So there are real management implications to these... an understanding of mating systems of waterfowl.

Chris Jennings: And that kind of leads me to, as you're discussing the very scientific aspects of this, and I'm approaching this as a duck hunter. What am I seeing in late December, mid January. I mean I hunted Mississippi for the last seven or eight years, and it was guaranteed that by like January 10th, I had pinto courtship flights over our blinds. People are like, "Oh look at those flocks of pintos" and like it was literally courtship flies and people didn't understand that these birds are actually setting the precedence for the breeding season now.

Mike Brasher: Yes, absolutely.

Chris Jennings: It's during hunting season.

Mike Brasher: Yes.

Chris Jennings: And then also, we modify our tactics to follow this behavior. I think duck hunters don't really understand some of the things that we do, are actually related directly to waterfowl behavior and the life cycle of waterfowl. As in these late season tactics that we talk about with less calling, less decoys, sometimes getting off the beaten path to find these small little pockets of water. But what you're actually doing is, you're setting it up for a pair bonding scenario to get away from the crowds. You're attracting these male, and sometimes female ducks into a smaller body of water that typically would be reserved for a pair bonding situation. And I think that's one thing that hunters may not really understand what they're doing as far as following the life cycle of ducks.

Mike Brasher: Absolutely. And that's why a hen mallard decrescendo can be deadly for a lone drake mallard, that's cruising above you. I can stomp on the brakes and set the wings hundreds of yards high, if he hears that... this because he's getting desperate.

Chris Jennings: He's looking for that.

Mike Brasher: It's later in the season. He's getting close to that breeding season. And there's a male bias sex ratio, more males than females. So some of the guys are going to be left out come breeding season. It's pretty cool to be able to understand what the birds are going through at that time, and to use it to your advantage as a hunter and in our case. The other thing that we'll caveat there, is that just remember that the timing of that pair formation varies among species. Mallards, black ducks, pintails, gadwalls those are some of your earlier pairing species. Divers typically pair later, and again, that relates to some of their foraging behavior and-

Chris Jennings: Divers are always out there doing weird stuff anyway.

Mike Brasher: Interestingly enough, one of the hypotheses for why divers pair later is that how do they feed? They dive. Well, when they dive, the male and female can't really see one another. So it becomes more difficult for the male to effectively stay with the female, and defend her from other males that may be trying to pair with her. So if you're a male, it's like I need to just wait until I get closer to the breeding season, to the breeding grounds. Otherwise, I'm risking pairing and losing track of this female. And so something as simple as that is one of the hypotheses that I've seen for why divers pair later. Teal are another species that pair later. That's really interestingly enough, that's believed to be related to their inability to carry back to the breeding grounds as meaning nutrient reserves as a larger bodied species.

Chris Jennings: So they don't pair until they get back up to the prairies or-

Mike Brasher: They're on their way back up. It's all hedging type thing. You don't want to wait too late, but then you don't want to be too early too because it's of no good, because one of the advantages of a hen being paired in the winter, is that she has access to better resources. It's been demonstrated many times that pairs are dominant to too lone, unpaired birds. And so a female wants to have access, and wants to have that protection, but that protection is only valuable if that female is of sufficient structural size in order to take advantage of those nutritional resources and carry them back to the breeding grounds with her.

Chris Jennings: That's one point, that brings it full circle really all the way back to habitat on the ground. I know Clay, our awesome podcast producer and I, we went up to Nebraska a few years back and there's, I don't think in my opinion, there's probably anywhere greater to watch courtship flights than in Nebraska in March in the rainwater basin. Nearly every species that you can imagine up there and you've got redheads, you've got pintails, gadwall, they're all, you can see these different courtship variations and it's a very impressive site.

Chris Jennings: But that's March, and now you're halfway, well probably three quarters of the way, back to the breeding grounds. Halfway for some for sure. And the importance of that habitat there, that stopover country is what we've used in reference to that rainwater basin area and how you'll have these tiny wetlands that will have 10,000 pintails on it and it's very impressive. And like you were talking about there, now you're talking about the nutrients and can they get that spring migration, the fulfillment that they need from the habitat to make that full migration all the way back to the breeding grounds to then get into their courtship behavior. So it all comes full circle right there.

Mike Brasher: It's one of the most fascinating aspects of waterfowl biology and an ecology to me. I'll leave you with this. One of the other sort of correlates to mating systems in waterfowl. We described how geese and swans and whistling ducks pair for life. And then we described how dabbling ducks are seasonally monogamous. What's the big difference between those groups when we talk about geese, swans, whistling ducks versus your dabblers and divers, other ducks.

Chris Jennings: Plumage.

Mike Brasher: Exactly. Technically it's called... Ducks, when you have a male and female that have different plumage, it's sexual dichromatism. The males and females are different color. The birds that pair for life, geese, swans, whistling ducks, the males and females are similar in appearance. They're monochromatic.

Chris Jennings: They don't need that flamboyant look to attract a male. Or female, I should say.

Mike Brasher: Sexually monochromatic. That's right. But just as I said, there are always exceptions. Think about model ducks. Think about black ducks.

Chris Jennings: That's right.

Mike Brasher: They're sexually monochromatic males and females are similar in appearance with some differences, the bill coloration. So there are always exceptions, and other examples that require you to delve a little bit deeper and ask the question, well, why did the males and females develop similar coloration patterns in that duck species, but not all of these others?

Mike Brasher: So it's a really fascinating area, both just from a general understanding of waterfowl biology, but as you pointed out, much of this discussion has very real application to where and why, and what time we delivered habitat conservation, or need the habitat on the ground to benefit these birds. And so hopefully we'll have an opportunity in the future to delve into some of these individual topics in a lot more detail with some other experts that we bring on because it's one thing to read about it. It's another thing to study it entirely, and I know there are some folks out there that can help us with some of these conversations, so it's pretty cool.

Chris Jennings: Awesome. Look forward to it. Mike, thanks for joining us. Thanks for dumping this vast amount of waterfowl mating systems knowledge on us.

Mike Brasher: My pleasure.

Chris Jennings: I'm sure the audience will benefit from it. A special thanks to our producer, Clay Baird does an awesome job getting the podcast out to our audience and special thanks to you, our audience for supporting wetlands conservation and listening to the DU podcast.

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.