New evidence from studies of migrating ducks is required reading for monarch-lovers
- Andy Davis
- Dec 27, 2025
- 4 min read
Hi blog readers,
Welcome to another edition of this crazy blog-thingy, where I break down the science that you need to know if you love monarchs. And today's topic is just that. You need to know this. Especially if you are one of those people who is STILL rearing monarchs in captivity, thinking you are helping, despite all of the scientific evidence out there on this practice.
I'm talking about some hot-off-the press research by teams of ornithologists and geneticists, who recently teamed up with duck hunters, to investigate the genetics of wild mallard ducks, like the ones pictured below. These are the ducks that you see on ponds throughout North America, often in cities, and, these are a migratory species too. These are also a species that duck-hunters love, and because of this, their North American populations are closely watched and studied.
The other important thing to know here, is that because of the heavy hunting pressure, there have been many private and even government-sponsored efforts over the years to "supplement" the wild population with captive-raised mallards. For decades, people that run private game preserves have been raising these ducks by the hundreds and thousands and releasing them to provide more birds for their hunters. There have even been releases of captive-raised mallards from other countries into the U.S.
All of these efforts have led people to wonder what happens if these captive-raised mallards mix (i.e. mate) with wild mallards, especially if the captive-raised birds are less fit. Well, now there are some answers to these questions, and the results are not good. It turns out that the captive raised mallards do have poor genetics. And it turns out, the captive-raised birds are indeed less fit. What's more, the annual influx of hundreds of thousands of these captive-raised birds into the wild population has now led to the "watering down" of the genetics of the wild population, so that many of the wild birds now have some of these captive-raised DNA in them.
In fact, genetic analyses of samples of thousands of ducks from around the U.S. has shown that in the Atlantic coast region, there are so many birds with captive DNA in them, that only 26% of all mallards there are completely "wild." The below picture is from a summary piece from Outdoor Life magazine.
Now, here is where it gets really scary. In recent years, ornithologists have also been studying the differences between captive-raised and wild mallards, and all of their research points to one conclusion - the captive birds are not good at migrating, and in so many ways. For starters, captive-raised mallards have shorter wings than they are supposed to have! They also don't eat as much or store as much fat as they need to before the migration period. If they do attempt to migrate, they often go in the wrong direction. They also require more and longer stopovers during the journey. You get the picture.
So, you can see how the genetic mixing of lots and lots of captive-raised birds into the wild population will eventually lead to problems, specifically in the migration ability of the (formerly-wild) population.
And apparently, the duck-hunters are now reporting that there are fewer mallards migrating than there used to be.
I'm going to put some links to some summary pieces of this research below, if you want to know more. Keep in mind that I only covered the basics in this post.
OK, so if you haven't figured it out yet why this is important for monarch-lovers, let me spell it out for you here - this situation is eerily similar to what is happening now with monarchs in North America, where we have millions of captive-reared monarchs being released by butterfly farms and hobbyists each year. Multiple research projects over the last decade have shown that captive-raised monarchs are not as good at migrating as wild monarchs are. Research has also shown that farm-raised monarchs have really, really bad genetics, to the point where their DNA no longer resembles wild monarch DNA, even though the butterflies "look" like monarchs. And to top it all off, we now have evidence that the annual fall migration of the monarch population has indeed been declining over the last two decades. All of this research is covered in prior blog entries, listed below. So you can see how this situation matches what is happening with the ducks.
Incidentally, I'll also point out here that this exact same situation is ALSO playing out now in the world of migratory salmon, where researchers in the Pacific Northwest have been studying their migration ability, and how it is being impacted by releases of millions of farm-raised salmon. Basically, the same thing is happening - the wild salmon population is getting watered down with all of the captive-raised DNA, and this is reducing the entire population's ability to migrate successfully. This research is also covered in one of my prior blogs, listed below.
As you can see, I keep tabs on these new findings from other taxa, especially where migration is concerned. We ALL should be doing this, in fact. Now that we can see the exact same thing happening to two completely different taxonomic groups (ducks and salmon), why should it come as a surprise that it would be happening too in the monarchs?
Please stop releasing captive-reared monarchs. Just stop.
Links to prior relevant blogs:
Let me end here with some full disclosure - I have a small flock of captive ducks, including mallards, on my property that I keep for eggs and sometimes meat! The flock has a huge coop and a well-built, caged run, and, they are fully spoiled by my kids. I can also tell you one thing I've noticed about them - they are not the smartest animals, nor are they even able to fly very well. That's all fine for my needs, but I can see first hand how bad it would be if these birds were to mix with any wild ducks.
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