How India’s coasts and estuaries help shorebirds and seabirds stay alive

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Shorebirds and seabirds in the order Charadriiformes are some of the most noticeable animals living near our coasts. Only passerines have more families and species than this group of birds, which are very different from each other. They live all over the world, from the Arctic to the Antarctic. They can be found on land and in the water, in almost any kind of environment. Because of this, their ways of breeding and moving are very different.

Even though it is clear that Charadriiformes is a single group, there has been debate about how the families in this group are related. According to the most recent research, the order is made up of three main groups: the Charadrii, which includes plovers, oystercatchers, avocets, stilts, and thick-knees; the Scolopaci, which includes sandpipers, snipes, jacanas, and painted-snipes; and the Lari, which includes sandpipers, snipes, jacanas, and painted-snipe (which includes skuas, skimmers, gulls and terns). The first two groups are often called “shorebirds,” while the last group is made up of “seabirds.”

Temperatures climb, the world burns, ice melts, pandemics erupt, and now the seabirds are dying.

Stay alive! I said to the gannets. I say it to geese, terns, every herring gull I see, raiding every bin. Stay alive! Stay alive!@KathleenJamie for @LRB https://t.co/vblfnVpWVu

— Iona Lawrence / @IonaLawrence@mastodon.social (@ionaflawrence) August 24, 2022

This article talks about a few important ecological aspects of shorebirds and seabirds, with a focus on the species that live near our coasts and estuaries and the biggest problems that need to be solved to protect them, both globally and locally. Shorebirds, which are also known as waders, are small to medium-sized birds that live on all continents and are often found in open areas, especially wetlands. Most of them spend at least part of their lives on tidal flats near estuaries or ocean shores. Others live in grasslands, rivers, lakes, and lagoons on land. Because these birds live in many different places and in different kinds of habitats, their bodies and bills have changed in many different ways. Shorebirds can use different food sources because their bodies look different. This lets them live together in large numbers at key spots along their migration routes. Flyways are routes that are used by several species and include all of the breeding, stopping, staging, and non-breeding areas that a population uses over the course of a year.

There are about 215 known species of shorebirds in the world. They live in 14 different families. Charadriidae and Scolopacidae are home to the most different species. Both in how they look and how they act, these two families are very different. Members of the Charadriidae family, which includes plovers and their relatives, have relatively big heads, short bills, and big eyes that help them hunt by sight. They do this by using a “run-stop-peck” strategy, which is thought to be the most basic way for shorebirds to hunt.

On the other hand, Scolopacidae members, such as sandpipers and their relatives, have bills that are longer than their bodies and come in different shapes (for example, upturned in godwits, straight in knots, decurved in curlews, wedge-shaped in turnstones). Most members of this family use touch to find buried prey, often using mechanoreceptors at the tip of their bills. Others use their tongues that look like brushes to eat biofilm.

One more big difference between Scolopacidae and Charadriidae is where they breed and how they move around. Most sandpipers live and breed in the north, but many of them make amazing journeys to the very south of the world. Most plovers, on the other hand, breed in temperate and tropical zones and don’t tend to travel far.

One of the most interesting things about shorebirds is that they can move from one place to another. Over 60% of the species of shorebirds move short distances or long distances. Several of its members do some of the longest and most dangerous migration flights in the world, travelling more than 30,000 km each year. Shorebirds move every year from places where they breed to places where they don’t breed, where they may spend up to ten months.

From an evolutionary point of view, migration strategies develop when the benefits of moving seasonally are greater than the benefits of staying in one place. But because the world has seasons, birds have to fly long distances, which takes a lot of energy. Different species have come up with different ways to migrate and go on trips of different lengths and times. Most species migrate by flying for short amounts of time and stopping for short amounts of time to eat and drink. This is called “hopping.” Others may fly long distances with breaks to rest and refuel (“skip”) in between. Lastly, in the worst cases, some shorebirds may make one very long migration flight (“jump”) instead of several short ones. Some species that live on the Indian shores and estuaries use the second strategy. They fly very long distances without stopping. Red knots fly about 8,000 kilometres in six days, and godwits fly more than 10,000 kilometres in seven days. Shorebirds’ long-distance migration flights are made possible by the energy and metabolic water they store under their skin, mostly as lipids but also as proteins in their flight muscles.

Shorebirds that migrate put down a lot of triglycerides right before they leave. At the same time, they build up their flight muscles without doing any more exercise. So, they can double their weight before they migrate. To do this, they spend a lot of time looking for food and eat a lot more during a period called hyperphagia.

Seabirds are birds that live in and get their food from the sea. This includes birds that live in coastal areas, estuaries, wetlands, and oceanic islands. Seabirds are in the suborder Lari of the Charadriiformes, which has about 127 species. Most of the time, gulls and terns make up this group on Indian coasts. From a morphological point of view, Lari is a group of different things. Small species weigh 170–220 grammes and have a wing span of 84–86 centimetres. Large species weigh 810–1,335 grammes and have a wing span of 128–142 centimetres. Some members can only eat a few kinds of food, so they are called specialists. Others, on the other hand, can eat a wide range of things, so they are called generalists. Also, they move across the equator and travel long distances through different oceanographic systems.

Seabirds are just as comfortable on land as they are in the air or on the water, and they often move from one to the other every day. To be so flexible, they must have unique physical and biological adaptations to an environment that has also shaped their behaviour, ecology, and population size. Their bills, feet, and body shapes have changed in many ways to fit different ways of life. This lets seabirds swim and dive using their webbed feet or even their wings to move through the water.

Even though all seabirds use their bills to catch and move food, they have different ways of using their bills for different kinds of eating. The Indian skimmer, which lives along our coasts, is a good example of a skimming boat. They have a special bill in which the lower mandible is longer than the upper mandible and is compressed on the side. This gives them a bigger surface area, which, along with the way they fly, helps them catch fish by skimming the water’s surface quickly with their lower jaw as they feel around for food. Not just bills have changed to help animals eat in marine environments. Since they eat in the sea, these birds also have to deal with high salt loads in their bodies. To do this, they use salt glands, which are organs that get rid of extra salt and are found in shallow depressions around the orbit above the eye. These salt glands help them deal with a diet that is high in salt. Also, like shorebirds, seabirds can handle fattening periods as a way for their bodies to adjust to migration.

“Life is the unknown and the unknowable, except that we are put into this world to eat, to stay alive as long as we possibly can.”
― Richard Bach, Jonathan Livingston Seagull#Nikon 📷 #NikonD7000 #SilverGull #NaturePhotography #wildlifephotography #shorebirds #seabirds pic.twitter.com/ubxWIOwShv

— Jacqueline M 📸🐦🐾 (@jacket1962) July 5, 2022

The seabirds are at the top of the food chain in the ocean. When they are breeding, they have to go fishing and then come back to their nest to bring food for their chicks. This is what ecologists call “central-place foraging.” During the time of year when birds aren’t breeding, social foraging is common, and usually involves more than one species. Foraging can happen during the day or at night, and it’s likely that these different times have come about because of how their prey act. Fish, crustaceans, and/or mollusks make up most of the seabird’s diet. But some species have started eating human-made things. To find food, different foraging strategies are used, which are usually related to the shape or function of the animal. Gulls pick up food from the ground, dive under the water’s surface, jump-dive, and do other kinds of diving to get food. For terns, well-known ways to catch insects are plunge diving, diving to the surface, dipping, and hawking. Some seabirds, especially gulls and skuas, scavenge for food. Most seabirds catch their food alive, but a small number of seabirds, like gulls and skuas, do this. Many species that eat leftovers have grown very quickly, and this is often put down to the fact that fishery waste has given them food for many decades.

Kleptoparasitism, which is when one animal steals food from another animal in a parasitic relationship, is another unique way to catch prey. Specialist kleptoparasites have adapted in ways that opportunist species don’t, like being able to find and attack hosts, carry food hidden in the proventriculus, stay in the air for a long time, and change their breeding schedule to match that of their host.

In the last few hundred years, there has been a rapid loss of biodiversity. One of the main reasons for this is the destruction and loss of habitats. This biodiversity crisis includes both species going extinct and the number of individuals in local populations going down. This can change the way communities are made up and how ecosystems work. Because of this, the numbers of both shorebirds and seabirds have been dropping by a lot. There are many reasons why population trends are going down, but climate change is one of the most important ones on a global scale. The effects of this threat are especially bad for species that live near the coast in places like estuaries and for those that breed in high latitudes, where climate change has already changed the ecosystem in big ways. Some of the biggest land-based threats are invasive alien species, native species that are causing problems (like those that have become too common), human disturbance, changes in land use and land cover, habitat loss, commercial and residential development, and hunting. Lastly, on the sea, some of the biggest problems are caused by bycatch (in gillnet, trawl, and other fisheries), pollution (oil spills, chemical contaminants, plastic, and marine debris), noise (busy shipping lanes, seismic surveys, and sonar), and prey depletion from overfishing, energy production, and mining.

Trouble in Paradise
In the last few decades, the Indian coasts and estuaries have been facing new threats and getting more polluted. Global data show that estuarine and coastal systems are some of the most heavily used and threatened natural systems in the world. This is true even though they provide important homes for many plants and animals and a wide range of goods and services for millions of people.

Because cities, industrial parks, and ports are close to coasts and estuaries, they have become contaminated with things like coliforms, hydrocarbon derivatives, pesticides, and heavy metals, to name a few of the most dangerous things. In recent years, problems related to the spread of alien species that are not native to the area have also become important. The ecosystem is protected by law, and both international and local communities recognise how important it is. This is a good sign that the Indian coasts and estuaries will stay a healthy ecosystem in the long run and continue to support shorebird and seabird populations.

Wildlife biologist Dr. Vaithianathan Kannan works for the Sathyamangalam Tiger Conservation Foundation Tamil Nadu Trust in Erode, Tamil Nadu.