The Science of Birds - Wetlands as Bird Habitat

Episode Date: September 15, 2021

In this episode, we’re going to look at wetlands as habitats for birds.We’ll start with how to recognize—how to define—a wetland ecosystem. Then, we’ll get into why these ecosystems are so important to birds. How do birds use wetlands as habitat? Next, I’ll highlight a few examples of bird species that depend on wetlands. Then we’ll talk about the conservation issues surrounding wetlands, and how their loss is affecting birds.~~ Leave me a review using Podchaser ~~‍Links of InterestWetlands InternationalWhere Are The World’s Wetlands? [Map]Support the show

I like the word swamp. To me, it's evocative and romantic, like the word jungle or archipelago. A swamp is a mysterious, maze-like place full of strange creatures and unknown dangers. What comes to your mind when you hear the word swamp? For some people, a swamp is just a muddy, smelly place crawling with snakes and humming with clouds of mosquitoes. I won't deny that this is an accurate description of, at least some swamps. Then we have bogs, bayous, fens, and marshes. Are these just different words to describe the same sort of place? What's the famous line from Romeo and Juliet? Something like, What's in a name? That which we call a swamp by any other name would smell just as fetid.

In fact, there are real significant differences between swamps, bogs, fens, marshes, and the like. differences that biologists and ecologists have sorted out over many decades of research. What we're talking about here are wetlands. A bog is one type of wetland, a swamp is another type of wetland, and so on. Wetlands of all kinds and all sizes are scattered across the planet. They're on every continent, from the polar regions to the equator. And wetlands are among the world's most biologically diverse ecosystems. So, not surprised. Surprisingly, wetlands tend to be jam-packed with birds. Sometimes they're practically overflowing with birds. Thousands of bird species depend on wetland habitats for at least

part of their yearly cycle. Waterfowl, shore birds, wading birds, grebes, flamingos, cranes, loons, raptors, kingfishers, and songbirds are some types of birds commonly found in wetlands. This ecosystem provides birds with vital resources like food and shelter. and birds themselves are often key players in the old circle of life in a wetland. As predators or as prey, birds can be integral members of the complex food webs in these watery environments. So birds need wetlands, and at least sometimes, wetlands need birds. And since we need birds, you and I, we should probably appreciate and value swamps, bogs, and marshes in all their mucky, smelly, mosquito-infested excellence.

Hello and welcome. This is the Science of Birds. I am your host, Ivan Philipson. The Science of Birds podcast is a lighthearted, guided exploration of bird biology for lifelong learners. In this episode, we're going to look at wetlands as habitats for birds. This is the first time I've created an episode that focuses on one ecosystem. In the future, I'll also do episodes for different types of temperate forests, tropical rainforests, grasslands, rocky shores, rivers, and so on. Today, we'll start with how to recognize how to

define a wetland ecosystem. Then we'll get into why these ecosystems are so important to birds. How do birds use wetlands as habitat? Next, I'll highlight a few examples of bird species that depend on wetlands. Then we'll talk about the conservation issues surrounding wetlands and their relationship to birds. All right, let's get into it. Most of us already have a sense of what a wetland is. It's easy, right? You got some land, you throw some water on it, and there it is. Now it's wet.

It's a wetland. How hard is that to understand? It's actually not as simple as that, is it? For example, most lakes are not considered. wetlands, at least not in a technical sense. And neither are rain puddles. So what makes a wetland a wetland? There are a bunch of different ways scientists have defined wetlands, and these definitions can get technical. We don't want to get into all that right now, so let's keep it simple. A wetland is a flooded area. It might be flooded for a few weeks or months every year, or it might stay

flooded for years at a time. So there's a cycle of flooding. Most wetlands dry up at least occasionally. The floodwaters are usually shallow, less than a few feet deep, and they flow slowly, if at all. True wetlands come in many forms, many flavors, but they all share a couple features, their soil and their plants. A wetland has what we call hydric soil. Growing out of that hydric soil are plants we call hydrophytes. I'm sure you recognize the root word there, hydro, which comes from the Greek word for water. Hydric soil is soil that's saturated by water, either for a season or two or year-round. Soil that's been waterlogged for a while has very little oxygen in it, and that's enormously important because the roots of most plants need oxygen.

Here's where hydrophites come in. These are aquatic plants that have adapted to growing in the low-oxygen hydric soils that characterize wetlands. Hydrophytes you might be familiar with include cat tails, water lilies, reeds, wild rice, papyrus, and duckweed. Which hydrophite species you find in a particular type of wetland depends on things like water depth, salinity, temperature, and the duration of flooding. Marshes, for example, are dominated by herbaceous hydrophites, like, reeds, rushes, and sedges. Marses typically lie at the edges of lakes or streams. A swamp, on the other hand, is a wetland associated with forest. Swamps have woody plants like trees and shrubs.

Likewise, bogs, fens, wet meadows, and all the other wetland types have special plants and physical characteristics that set them apart from each other. Collectively, all of these wetlands cover between 4 and 7% of the Earth's surface. That isn't a whole lot, really, when you consider the biological importance of wetlands at the global scale. A disproportionate amount of the world's biodiversity is concentrated in wetlands. Acre for acre, or hectare for hectare if you prefer, wetlands are as rich in plant and animal species as many rainforests and coral reefs. Why are wetlands brimming with so much life? Here are a couple reasons.

Number one, wetland ecosystems are rich in nutrients. Wetlands receive nutrients from the streams and rivers that flow into them. Those nutrients, combined with ample sunlight and water, power the food chain. The result is that wetlands produce enormous amounts of food. This is in the form of plants, insects, and other invertebrates, and on up the food chain to fish and birds. Reason number two. Wetlands are usually at the meeting place between dry, land-based ecosystems and fully aquatic

ecosystems like lakes, rivers, and the ocean. So in wetlands, you find terrestrial species rubbing shoulders with aquatic and amphibious species. It's a big party and everyone is invited. Some large wetlands can provide habitat for hundreds of bird species. For example, over 400 bird species are found in the Okavango Delta in Botswana. The Okavango Delta is one of the world's biggest wetland complexes. Every year, the Okavango River floods and then drains out over thousands of square miles in the Kalahari Desert. So this river never reaches the sea.

It forms an inland delta, an expansive oasis of pools, channels, and islands that regenerates every year. The floodwaters evaporate after a... few months, and the delta becomes relatively dry, and then the cycle repeats the next year. Among the many birds found in the Okavango Delta are species like the Makoa Duck, African Jakana, Slady Egret, African fish eagle, waddled crane, and Pell's Fishing Owl. Those of us who live in North America may be more familiar with another enormous wetland complex, the Everglades. Isn't that just the best name Everglades. I just love it. Anyway, this is an enormous swath of tropical wetland and

grassland in southern Florida. Here, too, you find over 400 bird species. Examples include red-breasted Morganser, mangrove cuckoo, wood stork and roseate spoonbill. The physical, geological conditions of the Everglades are unique. Seasonal floodwaters, leaving Lake Okeechobee spill across a vast shelf of limestone bedrock. The water flows slowly southward as a shallow river that's about 100 miles long. Oh, and the river is 60 miles wide. That's 60-60. Isn't that crazy? As far as I know, you won't find this dramatic combination of geology and hydrology anywhere else in the world.

Multiple wetland ecosystems have evolved in the Everglades, including wet prairie, sawgrass marsh, cypress swamp, and mangrove swamp. Together, these offer a wide diversity of foraging and nesting habitats for birds. There's a handful of other large and ecologically significant wetlands around the world. You may have heard of some of them. The Amazon River Basin and the Pontinol in South America, Kakadu National Park in Australia's Northern Territory, the Sunderbans in India and Bangladesh,

the Danube Delta in Romania. Seriously, who comes up with these super cool names? Okavango, Pantanal, Kakadu, Sunderbans, the Everglades. Whoever was in charge of naming these big wetlands, I say give that person a raise and a promotion. But wetlands don't have to be vast and globally significant like this to provide habitat for birds. There are countless small marshes, bogs, and seasonal ponds all over the place. Some are in relatively mundane locations, like at the edge of a golf course or in the state of

Nevada. There are a few wetlands within a 20-minute drive from my house. They may not be worthy of national park status, but they're great places to go birding. And there's a good chance that you too have a wetland nearby and that it's home to some interesting birds. From a bird's perspective, what's so great about wetlands? What do wetlands have to offer in terms of habitat? Well, wetlands are what biologists call highly productive environments. That means they generate a lot of biomass quickly. Most of the biomass produced in a wetland is in the bodies of organisms at the bottom of the

food chain. plants, insects, and other invertebrates like mollusks, fish, and amphibians. If you're a bird, all of those tasty plants and wiggling critters are like a big buffet waiting to be annihilated by you and your voracious buddies. Few other ecosystems offer such bounty to birds. And maybe this goes without saying, but wetlands have something else that's essential to birds. Water. You can imagine that wetlands are especially important for birds living in the desert.

Birds flock to these oases to guzzle water, if for no other reason. All that food and water in a wetland are pretty excellent resources, for sure. Birds need them to survive. But beyond mere survival, a bird is going to need lots of extra food and water if it plans to raise some chicks. This is one reason why so many bird species choose to nest in wetlands. These ecosystems also provide breeding and nesting habitats. On top of all that, wetlands can offer birds and their babies refuges from predators. After all, a duck paddling around aimlessly in the middle of a marsh is less vulnerable than a duck waddling around aimlessly on land.

And if you build your nest so that it's surrounded by water, it's like you've got a moat around your castle. Ground-dwelling predators like foxes, cats, and snakes should have a harder time getting to your nest. This might be why many wetland birds build their nests on mats of floating vegetation or on small islands. So wetlands are great habitats for birds because they provide food, water, nesting sites, and a bit of safety from predators. Some bird species live in the same wetland all year long. They stick around, riding out the yearly cycle of flooding and drying. The aptly named marsh wren, for example, is a nortland. North American species with many resident populations in wetlands.

But lots of other birds use wetlands for only part of the year. Some breed and nest in wetlands for the spring and summer, then move into other ecosystems for the winter. This might involve a long-distance migration to the other side of the world, or just flapping a short distance away into, say, a nearby forest or grassland. Another scenario is that a particular bird species might use one kind of wetland for breeding and another kind during the non-breeding season. For example, black-necked stilts in the western U.S. will often make their nests in freshwater

marshes far from the coast. These same birds might then migrate south to spend the winter in Mexico or Central America. There they hang out in salt marshes and mangrove swamps. So black-necked stilts use freshwater inland wetlands for breeding and salty coastal coastal wetlands when they aren't breeding. Migration in birds requires an outrageous amount of energy. Birds have to eat a lot to power their long-distance flights. This brings us to another opportunity for wetlands to make themselves useful to birds. As we've discussed in other episodes of the podcast, some populations of migratory birds

will gather in great numbers at so-called staging areas, where they gorge themselves on food. They fatten up to prepare for their long journeys. And where can birds find heaps and heaps of food? That's right, wetlands. Many of the world's most important migratory staging areas are indeed wetlands. Wetlands are also commonly used as stopover sites along migration routes. These are places where birds come down to rest and refuel for maybe a day or a week before moving on. breeding habitats, wintering habitats, staging areas, stopover sites, these are all vital for the

survival of birds. This brings us to the acronym IBA. No, I'm not referring to the Intelligent Badger Academy or the Impractic Bicycle Agency. IBA in this case stands for important bird and biodiversity area. I guess it should be I.B.B. but it's not, it's just IBA. Anyway, IBAs are sites around the world identified by the organization Bird Life International

as being, well, important to birds. There are multiple criteria for designating an important bird and biodiversity area. Maybe I'll do an entire episode on IBAs at some point and we can go deeper into that. For now, I just want to point out that

of the almost 14,000 IBA, across the globe, at least 40% are in wetland ecosystems. Some of these wetland IBAs are tiny. Take Chancery Lane Swamp in Barbados, for example. It has an area of only three hectares. But don't let that small size fool you. Chancery Lane Swamp serves as a stopover site for shorebirds migrating over the Caribbean islands. It also provides important feeding habitat for one particular species, the little egret.

Then there are much larger IBAs like Old Crow Flats, way up north in Canada's Yukon territory. Old Crow Flats covers an area of 800,000 hectares. Here, sedge marshes fringe the shores of about 2,000 small lakes and ponds. This area is home to half a million ducks and other waterfowl in the summer. Now let's take a closer look at wetland-dependent birds. These are species that can't live without wetland habitats. They need wetlands during at least one part of their life. Most of the world's so-called water birds are wetland-dependent species.

The term water bird is usually applied to ducks, geese, swans, grebes, loons, shorebirds, herons, ibises, and the list goes on. Basically, birds that splash around in the water. Waterbird isn't a very technical term, and its definition is, well, kind of ill-defined. Also, since biologists and other scientists are so enthusiastic about using hydro to mean water, hydric soil, hydrofights, hydrology, instead of water birds, shouldn't we be calling them hydro birds or hydro avians, hydravians? In any case, many bird species are wetland dependent, and that's especially true of water birds. Some entire bird families have a strong connection to wetlands. This is true for the family Raleady. These are the rails,

galanules, coots, crakes, and the like. These are classic wetland birds. Similarly, most members of the Jakana family and the Heron family are strongly wetland dependent. According to data from BirdLife International, at least 10% of the world's most endangered bird species depend on wetlands. We'll circle back in a few minutes to talk about wetlands and bird conservation. But first, let's look at a few representative bird species that are wetland dependent. The Black Turn, Clydenius Niger, is a member of the family Laridie. This is the gull family, which also includes the turns. The Black Turns breeding plumage is unusually dark for a species in the family Laridie. It has a black head and underside,

with silvery gray wings. It's a gorgeous, elegant bird. These turns live far out to sea or along tropical coasts in the northern winter during their non-breeding season. But in late spring, Black Turns fly to inland regions in North America, Europe, and Western Asia. They settle in freshwater marshes and get to work building their nests. The terns construct their nests so that they float on the water. The nest is a wobbly structure made of soggy vegetation. The eggs sit only a few centimeters above the water's surface. Some research suggests that the shells of Black Turn eggs are adapted specially to these damp conditions.

Black turns are highly social. They tend to build their nests clustered together in a wetland, in loose colonies. And these birds also forage together in flocks, ranging in size from a few individuals to more than a hundred. The diet of this species also seems to reflect its wetland-loving lifestyle. Black turns eat a lot of bugs. Other turn species eat mostly fish in the breeding season. Black turns eat some fish too, but they love.

to chow down on dragonflies, beetles, grasshoppers, spiders, and all those sorts of crunchy critters. Freshwater marshes are often teeming with invertebrates like these, even where fish are rare. Unfortunately, black-turned populations have declined in parts of their wide range. The major problem is that humans have, in many places, destroyed or trashed the wetland habitats of these birds. On that cheerful note, let's move on to our next example, the Reddy Duck, Oxyura Jamaicances. This funny little duck lives throughout North America, the Caribbean, and in parts of South America. The males are good-looking birds, with a chestnut-colored body, a black-and-white head, and a bright blue bill. The Reddy Duck is a diver. It swims around underwater, foraging

for aquatic invertebrates. Research on this bird suggests that its favorite food by far is midge larvae. Midgees are tiny flies. Their worm-like aquatic larvae are found in enormous numbers in some wetlands. Most of the world's population of ruddy ducks, over 80 percent, breeds in a special region of North America called the prairie potholes. This is a vast area of the Great Plains, spanning parts of the U.S. and Canada. The prairie potholes region is riddled with thousands of shallow ponds and other wetlands. These potholes formed about 10,000 years ago at the end of the last ice age. As the great continental glaciers receded, they left behind massive chunks of ice.

As one of these chunks of ice slowly melted away, it left behind a depression, and that depression filled with water to become a pond, a pothole. Thousands of years later, grasses and hydrophytes colonized the prairie potholes. And then came the midges and other aquatic insects. And hot on the heels of those insects were the ducks, including our friend, the ready duck. The wetlands of the prairie potholes region provide vital breeding habitat for a bunch of other duck species too, like the mallard, redhead, blue-winged teal, gadwall, and northern pintail. The PPR, those of us in the industry, call the prairie potholes region the PPR.

This region produces so many new ducks every year that people call it the Duck Factory. I know we're talking about verdant wetlands out under the open sky, but Duck Factory just makes me picture a huge industrial building complete with smokestacks. It's dark and greasy inside, full of clamoring machines, rotating gears, and criss-crossing conveyor belts. Everywhere you look, there are ducks on conveyor belts gliding by. They're quacking and looking mildly bewildered. Here are a bunch of ring-necked ducks, and there go some American widens. Ducks fall off the end of their conveyor belts, one by one, into big cardboard boxes.

Once filled with newly minted waterfowl, these boxes are taped shut and shipped off to all corners of the continent. It seems business is booming at the duck factory. The next bird I have for you is the snail kite, rostramus sociabalus. The snail kite is in the family of hawks and eagles. It's a raptor. But this ain't your grandma's raptor. This bird has a highly specialized and, frankly, sort of bizarre diet. And you know the punchline here. It eats snails. Not just any old snails, mind you, but apple snails. of the genus Pomasia. Apple snails are large, globular, and fully aquatic.

They live in wetlands. And therefore you find snail kites in wetlands. In the U.S., snail kites breed only in Florida, including the Everglades. The species is more widespread across Central and South America. The upper bill of this bird is sharp-tipped, narrow, and it curves downward. sharply. This sort of sickle or hook-shaped bill is ideal for prying apple snails from their shells. The plump snails are meaty and nutritious. So I guess it's not really that bizarre that a bird evolved to specialize in finding and eating them. It's just kind of crazy that the bird happens to be

a raptor. But just a quick side note here is that there's another wetland-dependent bird that specializes on eating apple snails. The Limpkin, Aramis Guarana. The Limpkin coexists with the snail kite in some of the same habitats. Apple snails are such good eating that two distantly related bird species independently evolved to prey on them. Only where you find apple snails in high densities will you find snail kites, more or less. The specific wetland habitat shared by the bird and its gastropod prey is defined. by factors like vegetation, water depth, water clarity, and the duration of flooding. Historically, there was only one species of apple snail in the U.S., in Florida.

But sometime in the 1990s or early 2000s, a non-native apple snail was introduced to Florida. We don't know exactly how the snail arrived, but it was probably some well-intentioned but misguided kid who dumped their aquarium out in the marsh. You're free, Mr. Snail. Now you can live in the wild. Go forth and multiply. This exotic apple snail is large, it grows quickly, it can withstand droughts, and it lives in large densities. It spread rapidly throughout the southeastern U.S. Research on snail kites has shown that the birds have actually expanded their breeding range into new territory, into places where this invasive apple snail has become established. This is interesting, right? Because it suggests that the presence of apple snails is the most

important habitat factor for the kite. To a snail kite, maybe there's nothing intrinsically valuable about a wetland. Wetlands just happen to be where all the food is. Not surprising, I guess. It's like me. I don't hang out at Taco Bell because of the convivial ambiance. No, I'm there for a high-quality cuisine. Cuisine that, if I've learned anything from experience, I will almost certainly regret eating in about 45 minutes. Moving on to one final bird for us to consider. The sharp-tailed sandpiper, callidress acumenata. The yearly life cycle of this bird parallels that of many other birds in the family scolopacety. It's a fine example of a shorebird. Sharp-tailed sandpipers are strongly migratory. In summer, they breed way up in Siberia, on tundra habitats at the edge of the Arctic Ocean. They aren't necessarily restricted to wetlands up there, but they frequently build their nests in or near mossy bogs. After breeding, these little birds fly all the way down to the southern hemisphere. Most spend their non-breeding season in Australia. Once there, sharp-tailed sandpipers do use wetland.

habitats. Compared to the black turn and snail kite, the sharp-tailed sandpiper is more flexible in the types of wetlands it occupies. Mud flats, salt marshes, flooded grasslands, inland marshes, rice fields, it's all good. Each of these wetland ecosystems is rich in food. The diverse menu for sharp-tailed sandpipers includes worms, insects, mussels, crabs, and other invertebrates. So the point here is that this sandpiper, A, isn't very dependent on wetland habitat for breeding, but B, it does depend on wetlands for the rest of the year. However, C, it makes use of a wide variety of wetland types, rather than just one or two. Humans have a complicated relationship with wetlands. On the one hand, we value wetlands, or at least we

used to because they provided us with clean water, plentiful plants to gather, and animals to hunt. On the other hand, humans have often viewed wetlands as wastelands, where disease and death await us. Swamps and bogs are spooky places in folktales where children go missing. Places inhabited by horrific creatures like the monster grendel in the story of Beowulf. The list of creepy wetlands found in literature and pop culture is a long one. Mostly, it seems, humans have simply treated wetlands as an annoyance, something that's in our way. The trend over thousands of years has been to drain or fill wetlands. We get rid of them to make room for agriculture, for cities and housing tracks, for man-made lakes, golf courses, amusement

parks, and so on. We also drain them to reduce breeding habitat for disease-carrying mosquitoes. As an example, in the early 1900s, the governor of Florida was hell-bent on draining the Everglades. Napoleon Bonaparte Broward, yes, that was really his name. Napoleon Bonaparte Broward wasn't the first or the last person who campaigned to drain the wonderful wetlands of Florida. To reclaim land for agriculture and development, Broward wanted to, quote, Drain that abominable pestilence-ridden swamp. So where has this kind of thinking gotten us?

Data from the organization Wetlands International shows that since 1900, 64% of the world's wetlands have been destroyed. And if we look further back in time, we have lost an estimated 87% of our wetlands in the last 300 years. Today, wetlands are one of the most endangered ecosystems. systems on the planet. Many are destroyed outright for development, agriculture, and grazing land. And even when they aren't completely destroyed, wetlands are vulnerable to pollution and over-fertilization from agricultural runoff. Human activities easily degrade these ecosystems.

Climate change may bring additional threats. For example, saltwater could drown some coastal wetlands as sea level rises. There's a lot of ongoing research into how resilient coastal wetlands might be in the face of rising sea level. It seems the jury is still out on that one. In any case, the catastrophic loss and degradation of wetlands over the last few hundred years means millions, or maybe even billions, of birds have lost critical habitat, habitat they need for breeding, overwintering, foraging, and migration. Okay, deep breath. So is the story of wetlands all doom and gloom?

Thankfully, no. Although wetlands are still disappearing and they face an onslaught of continuing threats, there is hope. In the last hundred years or so, scientists have learned a lot about the value of wetlands to human communities. We now know that wetlands provide us with ecosystem services. To name just a few examples of the services wetlands provide, we have flood control, water purification, groundwater replenishment, storm protection in coastal areas, and support for commercial fisheries. And most importantly, wetlands give people like you and me somewhere pleasant to go look at birds on

the weekend. I'm kidding, of course, but seriously, wetlands are awesome. them for so many reasons. Even people who don't give a hoot about birds, turtles, or alligators might be motivated to protect wetlands if they understand how these ecosystem services benefit human populations. Thankfully, millions of people out there do care about the birds, wildlife, and ecology of wetlands. Conservation organizations and governments in the last 60-plus years have been working hard to protect the world's remaining wetland ecosystem. And there has been a lot of progress in restoring wetlands, too. And you know how to restore a wetland, right?

You get some land, you throw some water on it, and there you go. Now it's wet. Congratulations, it's a wetland. Restoration complete. I'm going to lunch. If you haven't already, you might want to consider some ways that you can help protect wetland habitats and the birds that depend on them. Maybe support an organization like the Nature Conservatives.

or the Audubon Society. Or perhaps you can volunteer for a wetland restoration project in your area. Get out there and fix up your local swamp. And just like I'm trying to do right now, you can simply spread the word about the importance of wetlands, about how they're vitally important, not just for birds, but for us too. I hope you enjoyed our little expedition through the question,

Magmire today. Did you learn a few things? Are you looking forward to the next time you get to muck around in a wetland to see what birds are hiding in there? I sure am, especially after putting this episode together. I want to give a warm, fuzzy thank you to my patrons who support this podcast via Patreon. Their help makes this show possible, and it really motivates me when I sit down to write that next episode. My newest patrons are Jason, Kate, Aloncis girl, Pete, Gretchen, Chris, Patricia, Craig, and Meg. Thanks so much to all of you. Your support means a lot.

If you'd like to support this podcast, you can check out my Patreon page at patreon.com forward slash science of birds. You can always send me an email if you have something you'd like to share. Maybe a question or comment about the podcast, or perhaps you'd like to confess that it was you who dumped a, an aquarium full of invasive snails into the Everglades. In any case, my email address is Ivan at Scienceofbirds.com. You can check out the show notes for this episode, which is number 35,

on the Science of Birds website, Scienceof Birds.com. This is your once and future host, Ivan Philipson. I look forward to learning about birds with you next time. Cheers. Thank you.