Nature

A Little Nest That Nestles Where the Roses Bloom

A Cape Weaver bird lays the foundation of its complex hanging nest, woven of stout grass

The strict definition of a nest is a place where a bird lays its eggs and raises its offspring. Thus it can cover everything from a windswept cliff-ledge where a couple of Guillemot eggs roll around, to the snuggest woven structure a Weaverbird can prepare. Of course, the nest does not have to be in a tree. The simplest nests are the open scrapes of shorebirds, where the parents rely on the camouflage of their plumage and of the eggs to make the nest unnoticeable. A cliff-edge can house a few sea-bird eggs on bare rock, a rock-cleft can serve for a Puffin’s hideaway, or a huge mass of sticks can grow over the years to form an Eagle’s eyrie. Inaccessibility is the key to safety here.

How safe is a nest?

Some birds rely on communal nesting for safety. Large numbers of birds nesting together can discourage or bewilder a potential predator. Thus, we have the development of rookeries, where a group of tall trees will be filled with huge untidy nests and the raucous cry of the parent Rooks; or there are the riverside cliffs perforated with the multiple burrows of Sand-martins. Mostly, though, birds choose to hide their nests in deep cover, and breed in a small group. The nest may be hidden in a cleft or hole in a tree-trunk; it may be fixed firmly in the fork of a tree-branch; it may be in a cavity in a wall. It may even be in an old kettle or the engine of an abandoned car, examples of crossovers into the world of Mankind especially popular with Robins. The choice of nestsite is often reflected in the shape of the eggs, though these are by no means hardand-fast rules. Birds that nest in holes or cavities tend to produce round eggs, as there is no danger of them rolling away. Birds who make cup-shaped nests seem to produce lightly conical eggs, which can pack together rather more neatly. Birds that nest on open flat sites tend to have eggs that taper sharply. This has been interpreted as preventing them from rolling far, as they tend to roll in short curves, and allowing the eggs to be packed together much more tightly to enable the entire clutch to be covered simultaneously by the parent’s body.

How is a nest made?

When we think of a nest, of course, we picture the soft, reassuring, cup-shaped nest that used to grace the Nature Table at school. About three inches across, made of tiny interwoven twigs and grass stems, soft and slightly squashy, with a lining of feathers or, in some cases, a skim of dried mud. These familiar little nests vary of course in size, and in the details of their construction, but even an expert will be hard-put to identify the nest-maker, even if the eggs are present, from seeing the nest alone. The only safe way to be certain that you have identified the user of the nest is actually to observe the parent birds using it, sitting on eggs or raising their young. And of course, this must be done with enormous care, from a distance, without in any way disturbing or frightening the adults. Once you have found the nest, there is no need to keep watching it. Enjoy the comings and goings of the adults and, later, the fledglings, from a safe distance. The intricacy of the construction is what usually impresses with these little nests. When one considers that the entire structure has been built by means of a beak, by instinct, the feat is astounding. But these are not the most intricate nests by any means. The Long-tailed Tit, a not infrequent visitor to any garden, prepares a tiny nest, hidden deep inside a bush or dense tree, and strongly fixed in place. It is the size of a pint-pot, woven of fine twigs, soft grass and moss bound with spider-web silk. The entrance is near the top, and closes almost completely; inside, the nest is lined with between one and two thousand tiny feathers. Once the nest is nearing completion, one parent enters it and wriggles around to achieve the final roundness and smoothness. Then the egglaying can begin. As the family hatches and grows, the nest grows with it. It is elastic, and can swell considerably to accommodate the growing chicks and the parent bird (usually the female) that is feeding and tending them. The Swallows and House Martins have a very different approach to nest-building. These reject the usual nesting materials in favour of mud! We are all familiar with the cup-shaped nests attached to the eaves of houses. Everybody calls these “Swallow’s nests” but they are not. Only the House Martin builds like this, forming the nest from wet mud which it plasters in place then allows to dry before adding the next bit. The nests tend to be communal, but not closely packed. The same House Martins will return year after year to the same nest to breed. Swallows tend to nest in barns, building a cup-shaped nest of mud on a secluded beam or ledge. Swallows also will return to the same nest year after year. For both these species, it is good if you can provide an area of wet mud for them to use if the weather is dry. Swifts choose to nest in cavities in roofs or walls. They don’t use mud to line these, just an untidy scatter of twigs and dry nesting-material.

Birds’ nests you can eat

One bird, the Cave Swift or Swiftlet, a distant relative of the swifts that swoop over our fields in summer, lives in southeast Asia and north Australia. It builds its nest in caves, as its name suggests, fixed to the cave wall by the curious method of binding the nesting materials with its own saliva. Like most saliva, this contains a binding-protein called mucilage, which sticks together the twigs, feathers, bits of seaweed and so on that form the shelf-like nest, and also ensures it adheres firmly to the cave wall. The Swiftlet’s diet is exclusively insects, but the nest-building males gorge themselves on seaweed, which causes an overproduction of saliva for nest-building and also imparts a briny seaflavour to the ensemble, which is what aficionados of this bizarre delicacy crave. I am told that the nests must be soaked in water overnight, the bits of feather and faeces removed, then the resultant gelatinous fluid is added to a chicken broth base with onions, sake and eggwhite to produce the desired treat. As Hilaire Bellock wrote in On Food, Birds in their little nests agree With Chinamen but not with me

The supreme nest-builder

Probably the most accomplished –certainly the most flamboyant - nestbuilder is the Weaver Bird. These are a group of finches slightly larger than a sparrow, who live in the tropical Old World, chiefly Africa south of the Sahara and India and Burma. There are about 100 species, each with its own nest-building characteristics. However, they fall into two basic types; the communal and the social. All Weaver Birds have the instinct to build strong nests by weaving together long strips of palm-leaves or stout grass. They

Inside, the nest is lined with between one and two thousand tiny feathers

By Mike George

Mike George is our regular contributor on wildlife and the countryside in France. He is a geologist and naturalist, living in the Jurassic area of the Charente

A Mute Swan builds a large but relatively unstructured nest at ground-level

A large colony of weaver-birds' nests

A Long-tailed Tit standing on its nest of vegetable material bound with spider-silk. Note the opening near the top of the nest. The bird is bringing feathers to line the nest

Nest with eggs of a Blackbird. The cup of the nest measures roughly 5 cm in diameter

The curiously translucent nests of the Cave Swiftlet. It is these that are collected to make birds' nest soup

"Edible-nest Swiftlet" by Mike Prince is licensed under CC BY 2.0

are the only birds credited with an ability to tie knots! About 300 or 400 strips of leaf, often some 18 inches long, will go to make one nest, which will be broadly shaped like an inverted vase about 4 inches high with a nest-chamber and in some species an entrance-chamber as well. The entrance itself is usually at the bottom of the nest, and may in some species be extended out into an entrance tube. In the social Weavers, each nest is separate, but one tree may contain many nests, each hanging free on its thin but strong attachment from a branch. The Communal Weaver species cooperate in making a huge structure among the branches, containing several nests. This structure is often used year after year. Interestingly it is the male Weaver Bird that builds the nest. When it is half-completed, he will display and call on it until a female signals her readiness to partner him. At this point he will complete the nest. The female may make some additions and alterations, but chiefly her job is raising the chicks. The male may then make another nest and entice a second female to raise a family in it!

So how can I observe a nest?

The answer is, don’t! If you find a nest, back off and leave it be. Do not touch it or peer in to see the eggs or chicks. If the parents are away, they will return directly, and they may well be frightened off by your presence. Take a quick photograph if you feel you must, but it is better not to linger. From a distance, note the details of the nest (where it was, if in a tree or shrub, what that was, how high off the ground, what type of country or urban environment it was in, of what was it constructed). Wait at a safe distance to see if an adult bird visits the nest – that is the safest way to identify the owner. The important thing is to protect the nest-builders and their family. Your curiosity, laudable though that is, comes a poor second! If you want to follow the progress of a clutch of nestlings in detail, there are plenty of websites with nest-cameras, set up by trained professionals, which allow you to watch the chicks’ development. The BBC Springwatch program normally follows several. You will learn more from these than from watching a solitary nest in your own garden – and in comfort!