Fish Versus Feather: Georgia’s Salt Marsh Smackdown
At Science Friday, we love a smackdown, whether it’s a debate over which mammal has better sonar—dolphins versus bats—or which planet is the best to host signs of life—Mars or Venus? But when it comes to fish versus birds, we don’t need to manufacture drama. Nature gave us its own.
Corina Newsome, a graduate student at Georgia Southern University, was studying how seaside sparrows adapt to nest flooding, an environment where the most likely predators are animals like minks and raccoons. That’s when she caught on film a very unusual interaction: A fish entered a sparrow’s nest, and killed one of the new hatchlings.
Newsome joins Ira to explain what she saw, and how climate change is helping to turn the tables on this predator-prey relationship.
A Mummichog is depredating a Seaside Sparrow in the nest!
This predator-prey interaction was made possible by nest flooding…which is expected to increase with sea level rise.. pic.twitter.com/c00D4XMIZb
— Corina Newsome (@hood_naturalist) February 10, 2021
Help monitor bird populations and nesting success as a participant in NestWatch a national monitoring effort from the Cornell Lab of Ornithology. It’s the perfect time to start! Anyone, anywhere can become a certified NestWatcher, build nest boxes, and advance bird science. Visit NestWatch.org to get started in time for Spring!
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Corina Newsome is the co-organizer of #BlackBirdersWeek, Community Engagement Manager for Georgia Audubon, and a Masters student in Biology at Georgia Southern University in Statesboro, Georgia.
IRA FLATOW: This is Science Friday. I’m Ira Flatow. Here at Sci Fri you know we love a good debate. We’ve pitted Mars versus Venus, clash dolphins versus bat sonar, and now there’s some new contenders. Here’s Sci Fri producer, Katie Feather, telling us more about it. Hi, Katie.
KATIE FEATHER: Hey, Ira. Are you ready for another SmackDown?
IRA FLATOW: I am ready to rumble.
KATIE FEATHER: How do you feel about birds versus fish?
IRA FLATOW: Well, it depends on the wine you’re serving. Oh, you mean in a fight?
KATIE FEATHER: Yeah. Yeah, it’s usually the birds getting the better of the fish, right? Like, the fish are typically the prey, the birds are the predators?
IRA FLATOW: Yeah, that’s how it goes.
KATIE FEATHER: But Corina Newsome, a bird researcher and community manager for Georgia Audubon, captured the first ever instance of a fish predating a bird’s nest.
IRA FLATOW: No. How does a fish get into a bird’s nest?
KATIE FEATHER: Right? Well, this is where things get a little sad because these birds Corina is studying, seaside sparrows, they make their nests in these three foot tall marsh grasses. And with climate change their nests are getting flooded.
IRA FLATOW: I see. So the tide comes in, the nests are underwater now, and that sets the stage for the fish versus bird showdown,
KATIE FEATHER: Right.
IRA FLATOW: And she captured all this on video. If you ask me, that was kind of lucky.
KATIE FEATHER: Right? That’s what I wanted to ask her first. How did she happen to have a camera aimed at a nest at the exact right moment.
CORINA NEWSOME: So as part of my research for my master’s degree I’m studying nest predation in the seaside sparrow. I was actually focusing on mammalian nest predators like raccoons and American mink and rice rats, but the nature of having a camera on a nest is that you see anything that goes on behind the scenes of marsh life. And then one night there was a nest flooding event where a fish jumped into the nest. Was definitely not expecting that observation, but it happened to happen while I was looking for mammalian predators.
KATIE FEATHER: So what should we know about the seaside sparrow, the bird that you’ve been surveilling?
CORINA NEWSOME: So the seaside sparrow is a species of sparrow that when you look at it doesn’t necessarily stand out visually. It’s probably what you would imagine is the typical sparrow appearance. But they are a species that is found throughout the Atlantic and Gulf Coasts of the United States. And here in Georgia, you can see this bird in the salt marshes and you can actually observe them from some of the causeways that lead from, for example, Brunswick to St. Simons Island.
They live in these coastal marshes and they’re adapted to life in the salt marsh in a variety of ways. One of which, of course, being that they place their nest at a height of the ground that in theory, hopefully allows them to avoid nest flooding, which increases if they are lower to the ground. And the risk of nest predation, which increases if they are higher off the ground. If they happen to lose a nest to nest flooding, if a high tide is higher than they are prepared for, their offspring die in a flooding event. They’ll build another nest right away, but they’ll build it higher off the ground.
But because the threat of predation from terrestrial predators increases the higher a nest is off the ground, that of course, while relaxing, may be the threat of flooding increases the threat of nest predation. They’re essentially trying to optimize the perfect nest location to avoid those opposing threats.
KATIE FEATHER: How often did you catch something happening on these cameras and how many of them did you have out there for the study?
CORINA NEWSOME: So at one time I had somewhere between five and seven cameras that were active typically at one time. And whenever a nest would stop being active, whether it was because it failed from predation or flooding or abandonment for some reason or if it was successful and it fledged, I would move the given camera to a new nest. And so even though I was looking specifically at mammalian nest predation, there was all kinds of drama and interactions happening in the marsh. So I was able to catch nest predation happening from a mammal only about six times total.
I was able to also catch predation/territoriality from marsh wrens, which is another species of bird that lives in the same ecosystem as the seaside sparrow. They’re very territorial, about half their size and they would fly to sea side sparrow nests and poke holes in the eggs and fly away. So their whole goal was to make sure that that nest failed. And so I was able to catch some kind of interspecies interaction about 12 to 15 times over the course of my field season.
KATIE FEATHER: You must have gotten kind of attached to these nests when you were setting up these cameras. Like, I can imagine that you’re a little bit invested in the success of them.
CORINA NEWSOME: Yeah, definitely. So for starters, the labor of setting up a camera in a tidal environment with lots of equipment that’s sensitive to saltwater and putting it on a nest takes a whole lot of work. So I really, even for that reason alone, was wanting to see a nest succeed. But also understanding the threats that seaside sparrows are facing in their ecosystems currently and what they’re projected to experience in the future. Because of climate change, for example, sea level rise is expected to engulf the marsh so their habitat availability is going to be reduced and fragmented.
They’re also exposed to increased flooding events that is expected to increase the frequency of flooding. So understanding that they are facing a world of threats in the future and even currently makes me want every single nest that I see to be successful. That’s not always the case and there is an intricate web of interactions in the marsh. And the mammals that are out there serving as predators need to eat as well. And as much as it is a natural occurrence and a natural interaction, I was really sad any time a nest was not able to successfully fledge.
KATIE FEATHER: Yeah. And you were saying the predators need to eat, but apparently these fish do, too. So what do we need to know about this fish. Like, you don’t normally think of fish as a bird predator.
CORINA NEWSOME: Right. So this fish is called the mummichog, which is a very resilient, you could say, species of fish. They can tolerate a really wide range of environmental variables. They can tolerate wide ranges in PH, in dissolved oxygen. They’re extremely hardy. Some have even described this fish as the raccoon of the fish world because they can survive and eat a wide variety of items. They’ve even been sent to outer space to see how they adjusted in a weightless environment and they did just fine. So that pretty much tells you everything you need to know about the mummichog.
But because they’re omnivores, they can digest and do go after both plant and animal material. It’s not surprising that they would attempt to eat any kind of piece of flesh, right, in their path. But I was surprised to see how readily the mummichog went after a chick that, compared to the size of the mummichog, was fairly large, right? And it had no hesitation to grab it and start attempting to rip pieces of meal off of the chick while it was in the nest.
KATIE FEATHER: Yeah. Oh my gosh, just you describing the piece of flesh is sending me back to watching that video. It’s this video of this mummichog eating the baby sparrow. I was incredibly conflicted about it because it was fascinating and cool, but also somehow really upsetting. It was hard to resolve those feelings in myself when I was watching it. What was your first reaction when you saw this mummichog and the baby sparrow?
CORINA NEWSOME: So that sparrow hatchling was in the nest with two sibling eggs that had not hatched yet. And that hatchling had actually emerged from its egg earlier that day, so it was only hours old. And so when I was watching this video and I saw the water start to enter the nest, my heart broke because I think this chick is brand new to planet Earth, right? And the first thing it experiences is cold water surrounding it and trying to survive. But then when I saw the fish jump into the nest I remember screaming. I couldn’t even watch the rest before I started texting all of my friends and my colleagues and my advisor like, you all, a fish is in a seaside sparrow nest. What is happening.
And so I essentially kept watching the video and was live texting my colleagues. And then when I saw the fish grab the chick, because at first I saw the fish basically look up at the chick and I was like, it wouldn’t. And sure enough, it did. It grabbed the chick. And so while I am saddened right to my core, I was even tearing up. I had tears on my face. I was stunned. I could not believe what I was seeing. That was the most incredible, unexpected interspecies interaction that I have ever witnessed. And just the thought that like, these are the kinds of things that go on in the marsh at nighttime during high tide that people don’t ever get to see. Because I mean, who’s just going out into the salt marsh putting cheap video cameras on seaside sparrow nests.
So my mind was blown. I was very sad. But it was also very cool.
KATIE FEATHER: So can we assume that mummichogs may be making meals of little baby sparrows all the time in these marsh grasses?
CORINA NEWSOME: So it’s hard to know how frequently this interaction presents itself. Nest flooding is a threat that seaside sparrows have been facing for a long time, even before the climate change scenario that we’re in now because they have behavioral adaptations to this threat. But it would not surprise me if in fact, this was a relatively common occurrence for nests that were low enough to the ground where the tide was able to enter the nest. And once chicks are over a certain size, I wouldn’t put anything past a mummichog. But I would doubt that they would maybe pursue it as a food item as readily.
But since I released that footage in the publication and on social media, I actually heard from another woman who studies salt marsh birds and puts cameras on nests as well that she has seen fish coming up to an approaching seaside sparrows in the nest. So it is definitely happens and I think it’s probably a regular occurrence, though I don’t know how frequently.
KATIE FEATHER: Wow. This just opens up just a whole new side of the fish v birds debate SmackDown. Because you always imagine birds getting the better of fish and now the tables have turned in this scenario. It’s crazy.
CORINA NEWSOME: Exactly. And I am team bird through and through. But I will say, this was a cool win for the fish.
KATIE FEATHER: Could the seaside sparrow just find a more hospitable environment to live in because this one seems to be really attacking it from all sides.
CORINA NEWSOME: Yeah. So it would be great if seaside sparrows essentially had the evolutionary time to kind of adjust and maybe adapt to living in a slightly different environment that was not so threatened by climate change, but seaside sparrows are extremely well and specifically adapted for life in the salt marsh. They are adapted for drinking saltwater, right? Their renal system is really well equipped for that. Their eggs can survive for 30 minutes completely submerged without drowning. They’ve got all kinds of adaptations that set them up for life in the salt marsh.
But unfortunately, the threats from climate change are happening so quickly that there is really not time for something as drastic as an ecosystem change for a bird like the seaside sparrow. So our best bet for protecting this bird into the future and preventing their extinction is to make sure that their habitat is able to exist for as long as possible into the future and in as much space as it possibly can exist going into the future. And addressing the threats that are facing their habitat including sea level rise and exposure to nest predators. And hopefully those management techniques will help to preserve this species and prevent their extinction.
KATIE FEATHER: Well, we’ll have to leave it there. But this is such an interesting story and thank you for the work that you do and for bringing us this video and this new piece of information that no one knew was happening between fish and birds. And we appreciate you.
CORINA NEWSOME: Absolutely. Thank you so much for having me.
KATIE FEATHER: Corina Newsome is a master’s student in the Hunter Lab at Georgia Southern University and Community Engagement Manager for Georgia Audubon. For Science Friday, I’m Katie Feather.