The Science of Birds - Bird Habitat: Rocky Shores and Sandy Beaches

Episode Date: September 25, 2024

This episode—which is Number 104—is all about rocky shores and sandy beaches as bird habitat. These environments offer birds very different resources and challenges. We explore the geology behind these habitats—how high-energy waves shape rocky cliffs and headlands, while the deposition of sediment builds up sandy beaches. Alongside this, we discuss the dynamic interaction between birds and their coastal homes, and how species like gulls, shorebirds, and seabirds have adapted to thrive in these unique settings.The episode highlights the incredible diversity of bird species found along coastlines worldwide. From puffins nesting on rocky sea cliffs to plovers skittering across sandy beaches, coastal birds have developed specialized feeding and breeding behaviors to survive in their often harsh environments. We also examine how tides and wave energy shape the coastal ecosystem and offer rich feeding opportunities for birds during migration and in their non-breeding seasons.Finally, we touch on the many challenges coastal birds face from human activity—habitat destruction, disturbance, pollution, and climate change—all of which threaten these delicate ecosystems. But amidst the challenges, coastal environments remain awe-inspiring places for birdwatching, providing opportunities to witness some of the most dramatic bird spectacles on Earth.   ~~ Leave me a review using Podchaser ~~Link to this episode on the Science of Birds website Support the show

Ah, the seashore, such a romantic and exciting place to visit. Where else can you get sand kicked in your face by a bully on the beach? Where else are you as likely to welcome radiation from space to scorch your flesh? And where else but on the seashore can you start a small, woman-owned business selling seashells? The coast beckons us with not just the sound of crashing waves, but also the sounds of birds, like the iconic call of the herring gull, and the beautiful grunting calls of cormorants. We find all sorts of birds where the land meets the sea, sandpipers, Clovers, gulls, pelicans,

Gannets, raptors, puffins, and more. The mixture of species you encounter on the coast varies by season, habitat, and region. In many places around the world, birding on the coast can be super fun and rewarding. Wave-battered rocky headlands and sandy beaches are two of the important habitats used by birds in coastal areas. Patches of rocky and sandy shore,

are often found side by side, alternating along even a short stretch of coastline. But each of these two habitats is quite different. Each offers birds a unique combination of resources, opportunities, and challenges. Hello and welcome. This is the science of birds. I am your host, Ivan Philipson. The Science of Birds podcast is a lighthearted exploration of bird biology for lifelong learners. This episode, which is number 104, is all about rocky coastlines and sandy beaches, and the

ways birds use them as habitat. Different physical, geological processes create and maintain these two environments. and those processes influence which kinds of organisms can thrive there, from kelp, crabs, snails, and barnacles to fish mammals and birds. Today we'll start by looking at the physical properties of rocky coasts and sandy beaches, and we'll see how those properties interact with living things to create dynamic ecosystems. Birds are key players in those ecosystems all around the world, But birds use other coastal habitats too.

If you've ever taken a road trip along the coast, you've probably noticed that besides rocky cliffs and flat beaches, there may also be habitats like estuaries, mudflats, salt flats, lagoons, and mangrove forests. Each of these is an important habitat for birds, and I'll cover them in future podcast episodes. Today, however, we'll keep our focus on the rocks and the sand.

You know a rocky shore or a sandy beach when you see one. But what do you know about how these places come to exist, geologically speaking? Now, if you've got it all figured out, well, congratulations. You can just tap the skip forward button a few times on your podcast. tap. But for the rest of us, it's worth taking a few minutes to consider the basic geology of rocky coasts and beaches so that we can get a deeper understanding of how birds use these habitats. A section of shoreline can be classified into two broad types, which type depends on whether the shore is being actively torn down or built up. First, we have high-relief

erosional shorelines. High relief means having rugged topography, the opposite of flat, right? So this type of shoreline has steep slopes and prominent cliffs. High relief erosional shorelines are formed through the action of powerful forces of erosion, mostly from waves. Waves carve out awe-inspiring arches and sea stacks that protrude prominently into the water. The relentless erosion of rock, Day after day, year after year, shapes bluffs, cliffs, and terraces, resulting in an intricate coastal landscape. In North America, places with these features include the coasts of Maine, Alaska, and the Pacific Northwest. Countless other rocky shores exist around the world, from Ireland to northern Japan to Tasmania.

High-relief erosional shorelines are more common along the active margins between two tectonic plates, Uplift and volcanic activity are common where two continents are smashing into each other So there are more rocks being formed And more rocks being pushed up to form hills and mountains Also, the coast on these tectonic boundaries Usually has a narrow continental shelf A narrow steep shelf can allow more significant wave energy to build up

So that waves can directly slam into the shoreline with their full force Now in places where massive glaciers once flowed into the sea, like during the ice ages, fjords formed after the glaciers melted away and then the sea level rose by hundreds of feet, and that filled in the glacial valleys with water. Fjords and other rocky shores form some of the most majestic, visually stunning coastlines in the world. And high-relief erosional shorelines are also where you occasionally find hidden sea caves bristling with boobie traps, and pirate ships full of legendary treasure. Then we have low-relief depositional shorelines.

These have gentle slopes, sandy beaches, and sometimes barrier islands. But habitats like estuaries and mudflats are also in this category. Low-relief depositional shorelines are formed by the accumulation and deposition of sediments like pebbles, sand, and mud, which are carried by rivers or coastal currents. This results in wide, flat coastal plains that often have relatively calm waters and sheltered bays. The specific low-relief depositional shoreline we're talking about today is sandy beach. Beaches are characterized by rapid and extreme changes, making them highly dynamic environments. We find them more often on the passive margins of continents, like much of North America's east coast.

Sandy beaches are located in areas with low wave energy, a wide continental shelf, and significant input from offshore sediments. Now, even though these areas are defined by the deposition of material, that doesn't mean they don't experience some erosion. These are highly dynamic environments, after all. For example, currents and waves might deposit deep layers of sand on a beach in the summer, only for powerful storms to come along the following winter and strip away most of that sand. All of this exciting, sandy action happens in what scientists call the swash zone. This is the part of a beach that's regularly covered and uncovered by waves as they move up and down the shore. It's the area where water from breaking waves rushes up onto the beach, and that's called the swash,

and then it flows back down. That's called the backwash. Not to be confused with backwash, the thing you should be very concerned about when your friend asks if you want the last few sips from their bottle of mountain dew. The swash zone experiences the most frequent interaction between land and water and plays a crucial role in sediment transport, shaping the beach's structure over time. This zone extends from the waterline to the highest point waves reach during high tides, or when there are large. waves. Within the broader intertidal zone, which we'll talk about in a moment, most of the wave action happens in the swash zone. Now, what about Dunes? No, no, not Dune with a capital

D, the award-winning series of science fiction books and films. What with the spice and the giant sandworms and all that? No, I'm talking about Dune. on a sandy beach. Dunes form when wind transports dry sand inland from the beach and deposits it around obstacles like driftwood or plants, or I suppose, empty plastic bottles that once contained mountain dew. As the wind slows down near these barriers, sand accumulates and small mounds begin to form. Vegetation such as beech grass plays its part by stabilizing the dunes, trapping sand with their roots, and leaves, allowing the dunes to grow larger over time. As more and more sand gets deposited and with the anchoring effect of plants, dunes can become major features on the landscape,

serving as natural barriers. They can protect coastal areas behind them from erosion and storm surges. Other kinds of barriers can form along sandy coasts. The depositional environment can create structures like sand spits and barrier islands. These dynamic lands, these dynamic land, waveforms can slow down or block wave activity. They protect other vulnerable ecosystems found further inland, like salt marshes, tidal flats, and lagoons. So if nothing else, when you see rocky shores, think erosion. They're being torn down by the elements. And when you see flat sandy beaches, think deposition. These are being built up as new material is laid down. Here, in Oregon, where I live, our coast has beautiful examples of both types of shoreline.

We have lots of craggy headlands formed of black basalt rock. We've got dramatic cliffs, caves, and towering sea stacks. Sandwiched between these headlands are flat sandy beaches. And if you'd like to learn more about the geology of the Oregon coast, might I suggest you watch the 1985 documentary film called The Goonies? Great examples of sandy beach habitat are all over the place. Just to name a few, there's Southern California, the Gulf Coast of Texas, southeastern Argentina, southern Portugal, Sri Lanka, and the beaches around Perth, Australia. Now, so far, we've been talking about how the environment changes as you move along the length of the coast,

as you move parallel to the shoreline. But scientists also divide the shore into zones along the vertical column as you move from the ocean to dry land. There are three major zones that are important when it comes to bird habitat. First, there's the subtidal zone, which is below the low tide line. The subtidal zone is always underwater. Then, moving up higher, there's the intertidal zone. This is the area between the high and low tides. So the intertidal zone gets submerged by water and then exposed to air on a predictable cycle every day.

Finally, we have the supra tidal zone. This is the area above the high tide line that is only occasionally reached by the highest tides or by waves during storms. The supra tidal zone might get plenty of salty spray and mist from crashing waves, but it's generally dry. All right, so I think you get the picture when it comes to the physical settings of rocky shores and sandy beaches. We just covered the basics. Birds that feed and breed in these habitats do so in very different ways. And we'll get into all of that soon. But first, let's talk about the actual types of birds that hang out in these areas.

Yay, we're finally going to talk about birds. Thanks for sustaining your interests, or at least your patience, in getting this far, as we've talked about rocks, swash, and pirate caves. So, what kinds of birds do we have at the shore? Well, I could just say shorebirds and end the episode right there. Drop the mic, and we're done. But shorebirds is only a small part of the answer, isn't it? In any case, what is the definition of a shorebird?

Well, there's no single technical definition. It's like when I did an entire podcast episode on seabirds. These words, shorebird and seabird, each refers to a mishmash of species from multiple taxonomic families. They may not all be closely related, but they share similar habitats and some at a adaptations. Shorebirds are generally defined as a group of species within several families in the order Karadriaformis. They're adapted to life in coastal environments. The four main families of shorebirds are one, scolopacity, which includes the sandpipers, curlews, turnstones, and all of those little buggers. Listen to episode 26 of the podcast if you want to learn more about the

family, scolopacity. Two, caradreidae. These are the plovers, dotaroles, lapwings, etc. Three, recurverostradi, which is the family of the avocets and stilts. And four, hematipodidae, the oyster catcher family. Other kinds of birds rub shoulders with these shorebirds in rocky and sandy coastal environments. We'll consider them, too, as we explore each of these habitats separately. But one thing to keep in mind is that relatively few bird species spend the entire year on the coast. If you studied a single patch of rocky shore or sandy beach over the course of a year, you'd see that the mixture of bird species there changes from season to season. There's one mixture of birds in the breeding season, another during periods of migration,

and yet another in the non-breeding season. Another variable here is that some species, like many seabirds, always breed in coastal areas, while other species have more broad habitat tolerances. The common raven is an example of the latter. Ravens sometimes breed on coastal cliffs, but they also build nests in habitats like mountains and deserts, far from the sea. All right, let's visit some rocky shores to see what's going on with birds in this habitat. Some of the world's most dramatic jaw-dropping bird spectacles happen on sea cliffs. Above the crashing waves, many species build their nests in rock crevices or on ledges.

The air is filled with harsh calls, the pungent scent of guano, and flapping sea birds as they come and go to the cliff. I've had some awesome birding experiences along the rocky coasts of places like Iceland and Alaska. On one occasion in Iceland, a single cliff I visited was teeming with Atlantic puffins, razor bills, thick-billed and common mers, black-leg kitty wakes, gluckus gulls, northern Fulmers, northern Gannets, European shags, and, yes, common ravens. On bird cliffs like this, we're mostly looking at species that fall within the broad category of seabirds. And what they're doing is nesting, often in great numbers. Cliffs are relatively inaccessible to land-dwelling predators, so they make great places to raise chicks. But seabirds

are here for only the breeding season. And even then, they're still getting their food from the ocean. They forage in the water, either near shore or far out to sea. In contrast, most of the shorebirds that spend significant time in rocky habitats are not there to breed. Their only interest is hunting for crunchy or chewy morsels of food. Examples include black turnstone, reddy turnstone, surfbird, wandering tattler, purple sandpiper, and rock sandpiper. These species breed in places like the Arctic tundra, often away from the coast. But during migration and in the non-breeding season, you'll find these chunky little birds hopping around with sure-footed confidence on slippery rocks in the intertidal zone.

One affectionate name for this group of birds is rock pipers. Among other shorebirds, some plovers will also venture into rocky areas to find food. But I can't think of any plover species that really specialize in foraging among rocks. If you know of some, let me know. Of the 12 oyster catcher species in the family hematipodity, some both breed and forage along rocky shorelines all year long. Two species that are strongly associated with rocky habitat are the black oyster catcher and the blackish oyster catcher.

That's right. one species is named the black oyster catcher, and there's another one called the blackish oyster catcher. For real. Geez, while we're at it, why not have species with names like the off-black oyster catcher or the unquestionably black oyster catcher or the sooty oyster catcher? Actually, that last one is real. There is a species named the sooty oyster catcher. In any case, these species with black plumage are camouflaged against the dark wet rocks of

their habitat. Like the examples I gave in Iceland, some gull and turn species in the family Laredi breed on rocky shores. Another example is the Inca Turn in South America, which nests in cliff crevices or among boulders. In terms of gulls, many of them are generalist predators. They'll sometimes catch invertebrate prey among the rocks as well as make their nests there. Now look, I know that nobody likes penguins, but I suppose for the sake of being thorough I should at least mention penguins. All penguin species feed in open water, but in terms of where they lay their eggs, some species breed on rocky shores.

The Humboldt penguin, for example, has small breeding colonies on the rugged rocky coasts of Chile and Peru, and Galapagos penguins make their nests in crevices among volcanic rocks. Certain raptors will also nest on seaclifts. Examples include peregrin falcon, jeer falcon, and white-tailed eagle. One major group of birds that is not well represented in rocky shore habitats is that of perching birds, species in the order paceriformis. And I'm not really sure why that is. Maybe it's because this environment doesn't offer enough of what passerine birds like to eat,

like insects and or small seeds. But there are some exceptions. For example, the rock pippet, anthus petrosis, is a perky little songbird with dull, streaky, grayish-brown plumage. It breeds and forages among rocks on the coasts of northern Europe. Rock pippets eat all sorts of small animals, some of which are found in the intertidal zone among the rocks and seaweed, and others that are more terrestrial. So it seems it's at least possible for passerine birds to make a full-time living on the rocky coast. It's time to leave the rocks behind for a bit as we walk on the beach, wiggling our toes in the soft sand, trying not to get hit in the face by any stray frisbees, drones, or beach balls.

A sandy beach is, in some ways, a harsher environment than a craggy seacly cliff. at least in the eyes of a bird looking for a place to raise some babies. The beach is often more exposed to the sun and wind, and there may be fewer places to hide from predators. That said, quite a few birds do nest on beaches, and we'll get to that. But more often, the birds we see methodically patrolling or skittering across the beach are just there to find food, in their non-breeding season or during migration. Superficially, it might look like there isn't much food to be found on the beach,

and relative to rocky shores, that's more or less true. But many bird species have figured out that there is actually a lot to eat here, if you have the skills to find it. The dominant bird groups we see on beaches include shorebirds like sandpipers, plovers, and oyster catchers. Gulls and turns, too, are major players in beach environments. Sanderlings are among the most famous beach birds. They're the adorable little sandpipers that run around back and forth in groups on the wet sand as the waves move in and out.

Sanderlings breed on the tundra in the high Arctic, but they migrate south to spend the winter on sandy beaches around the world. Plovers of various kinds, which, remember, are in a different family from the family of sandpipers, are more common on beaches than in rocky areas. In North America, a couple examples are the piping plover and the snowy plover. Some populations of these species breed on coastal beaches. They make simple scrape nests in the sand, lined with small pebbles and shell fragments. Australia is home to a real beach specialist, the hooded plover, Caradrius Cuculatus.

This is a stocky, medium-sized plover with a blackhead, red eye rings, and a red bill. that has a black tip. Hooded plovers scamper around on beaches in southeastern and southwestern Australia. They make their little scrape nests between the high tide line and where the dunes begin. Some oyster catchers are more at home on sandy beaches than among the rocks. This is true for the American oyster catcher, for example, which prefers to breed and forage in sandy or marshy areas. In the family Laridie, turns and skimmers of Quite a few species breed in sandy coastal areas. Examples include Royal Turn, Australian Fairy Turn, and Black Skimmer.

As for gulls, yes, there are a bunch of species around the world that hang out on beaches, looking for their next big score. They hunt small invertebrates, they eat scraps of whatever lying around, and they harass other birds to steal their lunches. And when humans are on the beach, gulls like to swoop in brazenly to, to snatch French fries, pizza, chicken strips, or just about anything that we are trying to eat. Some gulls also nest in sandy areas, like on barrier islands. But I don't know of any gull species that nest exclusively on beaches.

Now I should mention that some birds in the family are deity also show up on beaches and rocky shores alike. These are the herons and eagrots. They stalk the shore for prey like three. fish and crabs. Examples I'm thinking of are the western reef heron, found on the coasts of Africa and southwestern Asia, as well as the Pacific reef heron, found across Southeast Asia and Australasia. Last and definitely least, we have the penguins. Uh, penguins. Perhaps the best examples of species that sometimes breed on sandy beaches are the African penguin and the Magellanic penguin.

At this point, we've got a sense of the general kinds of birds living in both rocky shore and sandy beach habitats. They spend time in these places to feed or to breed or both. Let's look more closely now at the food resources in the two environments. The sea offers a veritable cornucopia of edible delights. Most of the prey animals taken by birds, are at least partially aquatic and are adapted to salt water. They live in or at the edge of the sea for their entire life cycle. So we're talking things like fish and marine invertebrates like crustaceans, mollusks, and worms. Birds we typically think of as sea birds are the ones that catch fish and other prey out in the water.

They might forage close to shore or many miles out at sea. They eat mostly fish and squid. Seabirds come to the coast mostly just to breed, otherwise they spend the rest of the year on the open ocean, far from land. The vast majority of shorebirds, in contrast, are not swimmers or divers. They walk around on land in search of food. They peck and probe as they forage for small invertebrates, among rocks in the sand or in shallow tide pools. And speaking of tide pools, rocky areas in the intertidal zone are conspicuously rich with invertebrate life and kelp. Clinging to the wet rocks are critters like mussels, barnacles,

snails, limpetes, crabs, sea stars, and urchins. Tide pools are also teeming with anemones, small fish, and shrimp. When the tide is low and these prey animals are exposed to the air for a few hours, birds get busy foraging among the rocks and pools. But it isn't necessarily always easy pickings for the birds. Those marine invertebrates have adaptations to protect themselves. To resist both predators and the pounding surf, many of them attach themselves very firmly to the rock, like they're attached with crazy glue. It takes a lot of effort to pry them loose. Many invertebrates also protect themselves with spines and or thick shells. Earlier we talked about the rock pipers.

You know, species like surfbird, ruddy turnstone, wandering tattler, and the purple sandpiper. Well, some of these birds have strong, stout little bills that make it possible to tug and pry invertebrates off of rocks. Hard-shelled prey like mussels and barnacles are actually swallowed whole. They're crushed in the bird's muscular. gizzard, which contains small rocks or grit that work sort of like teeth to grind up food. There are also small intertidal animals climbing around on the rocks that aren't so firmly attached. These include crabs, slugs, and isopods. These guys try to avoid being eaten

by hiding behind boulders, under shells or small rocks, or among layers of kelp. But then along come birds like ruddy turnstones, black turnstones, and wandering tattlers, and they turn stones or shells with a flip of their bills. Or they probe into masses of kelp, crevices, and so on. I have some happy memories of watching groups of these plump shorebirds as they forage on the Oregon coast. There are often multiple species working the rocks side by side, walking and hopping along and snatching up prey. Things on the beach are quite different. A different suite of marine invertebrates is found in this environment. They're either on the surface of the sand or buried under it.

Crabbs, isopods, amphipods, and insects are common on the surface. Lurking under the sand are things like clams, shrimp, burrowing crabs, burrowing snails, and an assortment of worms. No, again, we're not talking about dune, so no giant sandworms. isn't dune. Shorebirds, gulls, and passerine birds foraging on the beach can hunt the surface dwelling invertebrates using their eyesight. Plovers with their big eyes are especially well adapted as visual hunters. But many sandpipers live up to their names by probing into the sand with their long bills. They can access all those weird critters beneath the surface. The longer the bill, the deeper the probing. So species with different bill lengths have access to different

subterranean prey. This mode of foraging depends on the sense of touch, on tactile sensations. Now on just about every beach in the world, there's another micro-habitat used by birds looking for snacks. And that is the rack line. Rack is spelled W-R-A-C-K. A rack line is the collection of debris that accumulates on a beach at high tide. Marine rack is a jumble of kelp, sea grass, seeds, drift wood, shells, exoskeletons, skeleton skeletons, fish carcasses and human garbage like styrofoam, plastic, nickelback CDs, and fishing gear. And also among the rack, you might find the occasional glass bottle sealed with a cork, and inside there's a rolled up piece of paper with a message scrawled by a lonely castaway begging for rescue.

To us humans, the rack line can be smelly and kind of unattractive with all that rotting kelp and dead stuff. But this is actually a really important part of the ecosystem on a sandy beach. The organic material washed up on shore is used by many organisms as food or shelter. Birds poking around in the rack can glean all sorts of small invertebrates to eat. Hiding in there are small critters like amphipods, isopods, and insects like kelp flies. So that was the rack line. And lastly, we have the scavengers.

Birds like gulls, vultures, and ravens get excited when the dead body of a marine mammal, large fish, turtle, or mermaid washes up on the beach. Something like a massive whale carcass is a glorious gift from the sea for a scavenging bird. It's a mountain of meat and fat. And all that rotting flesh attracts countless insects and other invertebrates. Those tiny critters in turn can become prey for other kinds of birds. This is where some passerine birds might be more commonly observed on the beach. For example, there's a published paper where a scientist observed a black Phoebe, picking insects off the carcass of a sea lion on the California coast.

The Black Phoebe is in the tyrant flycatcher family, Tyrannity. You wouldn't normally think of it as a beach-dwelling bird. Another species that is a true beach lover is the blackish Sinclodes, which has the scientific name, Sinclodes, Antarcticus. It lives on rocky, sandy, and grassy shores of southern South America and the Falkland Islands. And yes, it's true, I'm talking about. talking about another bird with the word blackish in its common name.

I'm not doing this on purpose, I swear. Black oyster catcher, blackish oyster catcher, black phoebe, blackish synchlodes. Geez. Anyway, this Sinclodes bird, it's also a passerine species in the family fernariadee. It catches insects and other small invertebrates wherever it can find them. That includes on mammal carcasses, on piles of poop in penguin and other sea birds, colonies, in the intertidal zone, on floating kelp beds, and along the rack line. And apparently the blackish Sinclodes is such a bold, opportunistic little bugger that it will

follow people around on the beach, snatching up any invertebrates they kick up. And this bird will even saunter into people's houses to scrounge for things like breadcrumbs and butter. Let's take a few moments now to consider how birds use rocky shores and sandy beaches as places to breed. As I mentioned, most true seabirds only come to shore because they have to. None of them have figured out yet how to make nests that float on the open ocean or anything like that. So they come to land to plop down some eggs and raise their fuzzy, loud, insatiable babies. By nesting at the bleeding edge of where the land meets the waves, seabirds can stay close to their source of food. Rocky cliffs are attractive to these birds because they offer some of the best protection against land-dwelling predators.

They are relatively safe places to raise chicks. Small, rocky, or sandy islands are usually the ones. the best option because they usually lack any terrestrial predators. In that case, the only predators to worry about are other birds. Space among the rocks is a limited resource. Competition for the most primo spots can be fierce. One way birds minimize competition is by using different microhabitats for nesting. So some species make nests on small ledges, others tuck back into deep crevices, some use burrows in patches of soil, and others nest on grassy slopes at the lip of the cliff. And often seabirds just make their nests side by side, crammed together on

tiny ledges. They make use of every inch they can get. But living in crowded colony conditions has some advantages. Aerial predators like falcons, scuas, and gulls are still a threat, so having lots of eyes, scanning the sky can help to alert the entire colony to any incoming danger. And as an individual bird, you are less likely to get singled out by a bloodthirsty falcon or whatever. You might get lucky and get lost in the crowd. Safety in numbers and all that jazz. As I mentioned, sandy beaches can be more hazardous as a place to lay your eggs. Birds that nest on beaches tend to make inconspicuous nests.

Simple scrapes in the ground, maybe lined with a few shells, are what many species make do with. The shorebirds, turns, and gulls that nest in the sand have eggs with camouflaged shells. And the chicks, too, have cryptically colored plumage. They blend in with the sand. The chicks are also precocial. They're born with a downy coat, eyes open, and ready to run if necessary. Besides the threat of predators, one of the biggest natural challenges for birds breeding on the exposed coast is storms. Nests can be destroyed by powerful winds and chicks may drown in the surging tide during a storm. On top of all the nests, the nests. natural challenges faced by birds in these coastal environments, there are a bunch of human-related

threats, too. In other words, anthropogenic threats. The list of these is long. It's estimated that more than a third of the world's human population lives within about 60 miles or 100 kilometers of the coast. And the population density of humans near the coast is twice the average global density. The results for birds and other organisms living on the coast have been decidedly not awesome. Most countries have developed or otherwise heavily degraded more than 50% of their coastlines. Flat sandy beaches are easier to develop than rocky shores, so the former habitat has been the most heavily affected by humans. Natural, relatively undisturbed coasts are few and far between. These are mostly in the far north of Canada, Russia, and Greenland, and they amount to

only about 15% of the world's coastline. So we're talking about habitat destruction at a massive scale. Problems exist even on beaches that still have lots of sand and that appear to be okay and semi-natural, because human frolicing and fun in the sun on these beaches can disturb foraging and nesting birds. I mean, all of our sand castles are probably disturbing to birds because they think our children are gearing up for some kind of medieval holy warfare, turning the beach into a bloody battleground. But seriously, people and their dogs on the beach stress birds by chasing them. And people accidentally crush eggs and destroy nests. Our cats kill birds on beaches. Other invasive species can cause devastation too. For example, hooded plovers in Western Australia are routinely

killed by non-native foxes. And let's not forget oil spills! The Deepwater Horizon oil spill in the Gulf of Mexico killed as many as 100,000 seabirds. The Exxon Valdez oil spill that happened in Alaska in 1989 may have killed three times as many birds, so 300,000. Oil spills are a lot of dramatic, singular events, but trash and wastes wash up on our coasts continually. The inundation of human-made objects on both rocky and sandy shores is insidious and seemingly never-ending. Pretty much every beach in the world is littered with all sorts of plastic that washes up with the waves. By some estimates, 46% of all shorebirds will have eaten some plastic in their lives. and about 25% of them will get entangled in fishing nets or other kinds of plastic garbage.

Birds that eat plastic can suffer a variety of ill effects. They might just die outright from choking or obstruction of their digestive systems. Or they might have reduced health and shorter lifespans. And plastics can also reduce a bird's ability to reproduce successfully. Okay, so far we have habitat destruction. destruction, disturbances because of recreation, invasive species, oil spills, and plastic waste. There can't possibly be anything else, right? Oh, wait. Yeah, there's one more big thing. Climate change. Of course, always climate change.

As the average global temperature increases, sea levels are rising. If rocky shore and beach habitats don't evolve, if they don't naturally migrate inland to keep pace with the rising tides, they can get wiped out. And as we all know, climate change is causing more frequent and more powerful storms. Hurricanes, typhoons, cyclones, whatever you want to call them, there are more of them and they're becoming more destructive. One way people have been trying to mitigate the threat of rising sea level and storms is with something called beach Armoring. Now, despite its name, Beach Armoring has nothing to do with the problem of sand castle proliferation and kids preparing for war by donning helmets and breastplates over

their bathing suits. In reality, Beach Armoring is a coastal management strategy that involves building barriers like seawalls and rock piles to protect shorelines from erosion and storm surges. By stabilizing the coast, Beach Armoring is supposed to defend infrastructure. and human communities against rising sea levels and extreme weather events. Notice that I said human communities, because beach armoring is pretty much all about people, not natural ecosystems. It can actually be a bad thing for ecosystems.

Because beach armoring disrupts the natural movement of sand and sediment, leading to increased erosion and loss of habitat for birds. It can also alter rocky shores by changing wave and, energy, and therefore changing the natural dynamics of that habitat. Basically, building massive artificial structures like this causes all sorts of problems for natural habitats, which shouldn't be too surprising, I guess. Anyway, these are just some of the anthropogenic threats to coastal environments and the birds that live in them.

I could certainly do an entire podcast episode on this topic. But that's enough doom and gloom for today. Don't you think? Many of my most memorable, awe-inspiring birding experiences have been in coastal environments. And many of my best non-birding experiences, too. There's just something magical about these dynamic places where the land meets the sea. They're poetic, but also fascinating from a scientific, ecological perspective. The enormous abundance of rich food from the ocean attracts birds from

many different lineages, and in some places it supports incredible numbers of individual birds. Birds have adapted to the natural dangers and often harsh conditions of life on the coast. The rewards must outweigh the risks. The many species can minimize competition and coexist because they've carved out their own ways of life, their own niches, by feeding a on different prey and nesting in different micro-habitats. And there's the seasonal procession of species, such that the way resources are exploited by birds changes over the course of the year. I don't know about you, but the next time I'm at the coast, I'm going to pay even more attention to what the birds are doing. I'm going

to give them some extra love and appreciation. That goes not just for the puffins, oyster catchers, cormorants, and sandpipers. But also for that most humble, standard-issue gull, standing on the beach alone, looking all pensive. I mean, what if we could hear that gull's thoughts? Maybe it's thinking, I don't like sand. It's coarse and rough and irritating. And it gets everywhere. I hope you enjoyed listening to Episode 104. After making this one, I am super pumped to get back out to the coast. It's been way too long.

I want to see some of these birds and these natural processes in action. I hope you get a chance to do the same. And hey, I'm happy to say we just hit the four-year anniversary of the Science of Birds podcast. Crazy. It's been so awesome to see the podcast reach more and more people over these four years. I get emails fairly often from people who've just discovered the podcast. And it's cool that if you're one of those new listeners, you're greeted with a back catalog of over 100 episodes to dig into now.

I love making this show just as much as ever, and I love the enthusiasm and passion of my listeners. Thanks for being so interested in birds that you put up with my dumb jokes. And thanks to all of my amazing supporters on Patreon, you guys aren't just spectators. you're taking an active role in making this podcast happen. A big welcome to my newest Patreon members. Ning, John Stoner, and Susan Karen Stinson.

Thank you all very much for the wonderful support. If you are interested in supporting this podcast, you can check out my Patreon page at patreon.com slash science of birds. You can also shoot me an email if you have something you'd like to share with me, like some deep thoughts about birds, about climate change, or maybe you're a digital marketing specialist for Mountain Dew and you want to give me a million dollars to drop some more not-so-subtle references to your fine product in my episodes? In any case, my email address is Ivan at Scienceofbirds.com.

Again, this is episode 104. You can check out the show notes for the episode along with a few photos of birds I talked about today on the Science of Birds website, scienceofbirds.com. Ivan Philipson, I wish you a joyful day. Cheers.