You can tell a lot about the state of a Baya Weaver’s love life from the condition of his nest. These birds are among the most accomplished avian architects in the world. Their lovely homes are made with fine strips harvested from grass, paddy or palm fronds held together by elaborate knots. It takes approximately 1000 strips and hundreds of trips for a bird to complete a nest.
A male bird displays his skill for his partner when he weaves his nest. When it’s half done, and in the ‘helmet stage’, he begins to call out to passing females, flapping his wings and inviting them to drop in. He’s left it half done, so she can come and inspect it, noting how tight the weave is and whether he has chosen the location with care: is it high enough on a tree? Are the branches thin enough to discourage predators? Everyone knows that the best nesting locations are thorny branches, overhanging water.
Only once his nest wins her approval, will he complete their home and add a long entrance tunnel. By ensuring their doorway is suspended upside down, he is making it harder for water to seep into the home or for a predator to creep in. Sometimes, his partner will help with the interiors, adding tasteful bits of mud to help seal the nest and stabilise it in strong winds.
Considering all this, it shouldn’t be a surprise that Rahula Perera, an avid birdwatcher and a trustee at the Federation of Environmental Organizations (FEO) in Sri Lanka, is used to seeing incomplete nests – each nest representing a rejected young suitor who still has skills left to master. However, he knows practice makes perfect. “The male will get better at building a nest, and next year or the year after next, he will win a partner,” says Rahula.
A nest to call their own
When you hear the word nest, you’re likely to think of a cup-shaped construction made of twigs and grass perched on a junction of a tree. However, as demonstrated by the Baya Weaver, nests actually come in an extraordinary variety of shapes, sizes and utilize different building materials. Some are perched on a branch, but you could equally find one hanging under it, buried in the soil or even floating in the middle of a lake; some are lined and padded, others just sit on bare rock.
Nests are primarily built to protect eggs and then give hatchlings the protection they need as they mature. In order to construct a sturdy abode, birds become clever foragers, finding raw materials all around them. For instance, when Rahula sees Sunbirds flying close to the walls of his home he knows they are in pursuit of spiders – the insects will make a quick, tasty snack, and their webs are essential raw materials for a Sunbird nest. In this case, it is the female who does most of the building, and she uses the sticky threads to help suspend her nest from a large leaf. If you have a small water body in your home, you might even find a Sunbird nest hanging above it, says Rahula explaining that the moisture can help the birds ensure their eggs, which are sensitive to dry air, enjoy optimum conditions.
Other birds don’t just prefer to hang above the water, they want to be on it. The Little Grebe, which can be seen in Wilpattu in September, constructs a floating platform made from twigs and submerged aquatic vegetation. They build in shallow waters, so they can anchor the nest to the bottom, and will rely on surrounding vegetation for camouflage. When the eggs are laid, the birds cover them with plant material, both to hide their nest from sight but also to maintain the right temperature and humidity which will allow the eggs to hatch.
Whether they’re building in the trees, on the water or in a hole in the ground, many birds are simply doing the best they can to protect their young.
Nature vs Nurture
Looking at this dazzling array of models, it would only be natural to wonder, how do birds settle on the kind of nest they want to build? Most species build distinctive nests, and they’re born knowing what to do, says Rahula, adding however that there is also experience involved – the Baya Weavers, for instance, can learn and become better nest builders over time.
Another example of this are the Yellow Billed Babblers. These gregarious birds are called the Seven Sisters by locals in Sri Lanka, because they so often appear in groups. However, experts know these aren’t just a set of siblings, rather it’s a big family, comprising a mother and father, and two sets of children from different clutches. The older batch helps raise the younger, and they learn from their parents as they do it, Rahula explains. Nest building is an important aspect of their training and the young birds learn how to construct and maintain large bowl-like nests using roots, dried grass and even coconut husk as their base materials.
Birds are able to accomplish these feats of architecture using basically their beaks and claws, and it’s lucky that the former are so reliable. Whether used to delicately weave together a cup for a nest, or to hammer out a hole in a tree, the beak is the tool of choice.
Woodpeckers in Sri Lanka come in nine different species, but they all have straight, hard, wedge-shaped beaks designed to chisel wood. Tapping noisily at trees, they pry away the wood and fish for fat, delicious larvae with their long tongues. Sometimes, they keep chipping away until they excavate an opening 6 to 18 inches deep. The new nest is then lined with wood chips and made ready to hold 2 – 5 eggs.
So safe and warm are these nests, that they are much in demand with other birds including owls and hornbills. However, the Sri Lankan Grey Hornbill will sometimes add another layer of protection – before the eggs are laid, the birds seal the female off in the nest behind a fortress of mud, droppings and fruit pulp in order to keep predators out. The female is completely reliant on her partner to feed her and their children through a narrow slit in the wall.
Whatever shape and form they take, nests reflect not just the environmental challenges, but also the lifespan and size of the bird in question. “Large raptors typically use the same nesting location over many years,” explains Rahula, noting that they will redecorate, repair or replace parts of the nest as needed before laying a new batch of eggs. On the other hand, smaller birds such as the Red-Vented Bulbul might build a new nest every season, sometimes in a lampshade in your house! All birds choose their location with care – trying to ensure nests are not vulnerable to the weather, or to predators.
Camouflage
When push comes to shove, many birds will risk their own lives to protect their young. In fact, the most motivated actor in the world is a Lapwing with something to hide – a nest full of tender eggs. “They call it a broken wing display,” says Rahula explaining that if a predator gets uncomfortably close to the nest, the bird will land a few hundred metres away and pretend to be injured while calling loudly. “It’s trying to lead you away from its nest.” Researchers have found that nesting Lapwings sometimes modify their behaviour if they’re suspicious about a watching human – they may even make ‘false nest visits’ to throw you off the scent.
The birds are forced to go to such lengths because they are nesting out in open country, often perched on a slight mound. It helps that their eggs, and later the chicks, tend to be well camouflaged – combined with their parents’ brave antics, this is often enough to keep them all safe. However, like many other ground-nesting birds, Lapwings are especially vulnerable to predators and human-related impacts, especially in agricultural areas.
Rahula has a profound admiration for these plucky birds. “We might think a Baya Weaver nest is more advanced, and involves greater skills, but at the same time you have to have guts to lay your eggs out on open ground.” Only birds who are completely assured in their ability to camouflage themselves perfectly would risk it. “For me that’s an even greater creation,” says Rahula. “However you look at it, every nest is a masterclass in how to build a home to suit your habitat and your environment.”
Box: Nest observation etiquette
The study of birds’ nests is known as caliology. Birds themselves are quite careful about approaching their chosen nest site, and many will pause, and look around before they plunge into a hedge or shrub. You may see them collecting the material, or hovering near a particular branch as they begin building.
Nests are so distinctive that experts sometimes need to take just one look before they can tell you which species built a particular nest. And if you were still in doubt, you could peek in and identify the bird by the eggs. If you’re keen on observing a nest and are in a position to do so, ensure you keep your nest visits to a minimum and avoid encroaching on them during the first days of incubation when it’s critical that the eggs be maintained at the right temperature. Parents seeing you approach the nest, may feel compelled to leave, so try not to visit unless they’re out foraging for food.
Never handle birds or eggs in the nest – eggs can be easily cracked, and small nestlings are fragile. Remember that smart predators might be watching you, and could follow in your footsteps.
Keeping all this in mind, Rahula says the right etiquette is to simply leave the nest alone: “This is the period in which the birds are most vulnerable to predators,” he explains. “You don’t want to draw attention to them at this point.”
