Building castles in the air

The common bird's nest is a miracle of engineering and design, involving everything from spider's egg silk to feathers. Simon Hadlington reports

Of all the great architects of the animal kingdom - beavers with their dams, termites with labyrinthine mounds, wasps with papery nests - perhaps the most prominent are the birds. Each spring, millions of nests are constructed, using a vast array of materials, natural and man-made. Most are disposable - they are used for one season only - and yet they can be remarkably elaborate.

Of all the great architects of the animal kingdom - beavers with their dams, termites with labyrinthine mounds, wasps with papery nests - perhaps the most prominent are the birds. Each spring, millions of nests are constructed, using a vast array of materials, natural and man-made. Most are disposable - they are used for one season only - and yet they can be remarkably elaborate.

But despite their ubiquity, birds' nests have received surprisingly little attention from naturalists. Dr Mike Hansell, a biologist from the University of Glasgow, is trying to put that right. For many years, he has had an interest in the behaviour of animals that build structures, and in the early 1980s he turned his attention to birds' nests.

A search of the existing scientific literature revealed that birds' nests had not been studied in as much detail as might have been expected considering their range and number. Furthermore, there are few extensive collections of nests in museums around the world. "I feel very strongly that if you want to understand what birds are all about in terms of their natural history, you must have a collection of nests," says. Hansell,who has begun a collection of British birds' nests at the Hunterian Museum at the University of Glasgow.

Birds' nests appear to be incredibly complicated constructions. But on closer inspection they usually follow a relatively simple, if elegant, design. Hansell has identified four distinct components or "zones" of nests - some may include them all, others only one or two. The principal structure is the cup, which holds the nest together. Lining the inside might be a layer of insulation, while the outside might be clad in a thin skin of material, often for camouflage. Finally, if a nest is suspended - from a branch, say - it requires some sort of supporting mechanism.

One type of nest that the Glasgow researchers have studied closely is that of the long-tailed tit. In early spring, the males and females work together to build what Hansell describes as one of the most impressive-looking nests of any British bird. Typically, it is located in a gorse bush or bramble thicket, and is domed, giving an egg-shaped appearance with an entrance in the side.

Hansell has discovered that the long-tailed tit uses a Velcro-like substance as its main building material, which greatly simplifies the task of assembling the nest chamber. "The main part of the nest consists of a bag of a particular type of moss held together with a particular kind of spider silk," he says. "The silk comes from spiders' cocoons, the fluffy wrapping around spiders' eggs. The mosses that are used have small leaves. These become entangled in the loops of the silk - so there is the hook-and-loop principle of Velcro."

It has been known for a long time that spiders' silk is used in nest-building, but it had been assumed that the part used was the sticky silk from the web - rather than the eggs - whose tackiness was important for holding together the structure. "The bird begins by making the floor of the nest, then building up the walls with the moss-and-silk mixture," says Hansell. "What is wonderful about Velcro is that you just slap the two sides together and it sticks. So, from the birds' point of view, there is no especially complicated behaviour involved. While the structure does appear remarkably elaborate, it is not that difficult to assemble once the appropriate materials have been mixed."

Once the nest chamber has been built, the tit clads the exterior in a thin covering consisting of flakes of pale lichens and white flecks of spider silk. Often, pieces of polystyrene or fragments of newspaper are used. Finally, the inside of the chamber is insulated. Each long-tailed tit's nest is packed with about 1,500 feathers. "This in itself is interesting because the birds nest quite early and frankly there are not a lot of feathers to be found lying around," says Hansell.

One of the aspects of nest-building that has intrigued him is how birds manage to locate such large quantities of specialised construction materials. To attempt to understand how long-tailed tits found feathers, the Glasgow researchers planted piles of marked pigeon feathers in the vicinity of nesting birds near to Loch Lomond. At the end of the nesting season the nests were collected and the feathers removed and counted.

"From this work it turned out that the birds would fly only maybe 100 metres to find our feathers, and the feathers we planted made up less than 3 per cent of the total number in a nest," Hansell says. This seems to demonstrate that, despite an apparent absence of feathers, the tits have evolved ways of locating plentiful supplies. Often, large numbers of feathers from a given type of bird are found, suggesting that the tits locate a carcass, or a "plucking post" used by a sparrowhawk to strip its prey.

The relative simplicity of nest-building is an important evolutionary feature, Hansell believes. "If you look at a bird, you can hazard a good guess at what it feeds upon but you would have no real idea about what kind of nest it builds," he says. "A pointy beak will indicate that it is likely to eat insects, or a short, stubby beak that it is adapted for cracking seeds. A bird is anatomically adapted for feeding, but not for nest-building." So building a nest is all down to patterns of behaviour, rather than the possession of any physical adaptation. Because of this, there will be evolutionary pressure to ensure that building behaviour is as uncomplicated as possible.

Birds will tend to use a limited range of building materials, for example. "This is nicely illustrated by the blackcap warbler, whose nest is made entirely from the stems of grass," says Hansell. "The bird simply takes a dead grass stem and buckles it at points along its length to create a polygon. It stacks many of these up, one upon the other, with the distance between the buckling points getting greater - so creating larger polygons. The end result is a cup-shaped structure of extreme elegance and one that conveys a strong sense of 'design', and yet consists only of one building material and one building routine. This is often a feature of birds' nests: a beautifully designed nest can be made from very simple rules applied in a very simple way."

The Glasgow team has also been investigating whether there is a correlation between the size of a bird and the size of its nest. "You might think that a bird's nest would be more or less the same size as the bird," says Hansell. "In fact, we find a huge variation. A song thrush's nest, for example, does weigh about the same as the bird. But a humming bird's nest weighs only about half as much as the adult. At the other extreme is something like a magpie. Here the nest consists of a lot of large twigs lined with mud, often with a canopy over the top. This can weigh 20 times more than the bird."

Hansell says that the relative size of nest could be important in avoiding predation. "The humming bird is small, so it might make as small a nest as possible to help conceal it. There is no way that a magpie can hide its nest, so it builds a heavy, highly fortified structure to make it difficult for a crow to nip in and grab an egg." A white stork's nest, constructed from twigs, grass, rags and paper, can grow to more than 2 metres across and 3 metres deep.

For Hansell, the study of birds' nest-building behaviour is a crucial part of their natural history and one that should be given greater significance. "People often express wonderment at the ability of some birds to use tools. And while this is undoubtedly astonishing, I do feel that when you look closely at how a bird constructs its nest this is at least as awe-inspiring."

Rumer was diagnosed with bipolarity, attention deficit hyperactivity disorder and post-traumatic stress disorder: 'I was convinced it was a misdiagnosis'
peopleHer debut album caused her post-traumatic stress - how will she cope as she releases her third record?
A long jumper competes in the 80-to-84-year-old age division at the 2007 World Masters Championships
FootballGerman sparks three goals in four minutes at favourite No 10 role
Arts and Entertainment
'New Tricks' star Dennis Waterman is departing from the show after he completes filming on two more episodes
tvHe is only remaining member of original cast
Lewis Hamilton will start the Singapore Grand Prix from pole, with Nico Rosberg second and Daniel Ricciardo third
F1... for floodlit Singapore Grand Prix
Life and Style
Walking tall: unlike some, Donatella Versace showed a strong and vibrant collection
fashionAlexander Fury on the staid Italian clothing industry
Arts and Entertainment
Gregory Porter learnt about his father’s voice at his funeral
Arts and Entertainment
tvHighs and lows of the cast's careers since 2004
Life and Style
Children at the Leytonstone branch of the Homeless Children's Aid and Adoption Society tuck into their harvest festival gifts, in October 1936
food + drinkThe harvest festival is back, but forget cans of tuna and packets of instant mash
New Articles
i100... she's just started school
ebooksAn unforgettable anthology of contemporary reportage
New Articles
Life and Style
Couples have been having sex less in 2014, according to a new survey
Arts and Entertainment
musicBiographer Hunter Davies has collected nearly a hundred original manuscripts
New Articles
i100... despite rising prices
Holly's review of Peterborough's Pizza Express quickly went viral on social media
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Volunteer Trustee opportunities now available at The Society for Experimental Biology

Unpaid Voluntary Position : Reach Volunteering: Volunteer your expertise as Tr...

Early Years Educator

£68 - £73 per day + Competitive rates of pay based on experience: Randstad Edu...

Nursery Nurse

£69 - £73 per day + Competitive London rates of pay: Randstad Education Group:...

Primary KS1 NQTs required in Lambeth

£117 - £157 per day + Competitive London rates: Randstad Education Group: * Pr...

Day In a Page

Scottish referendum: The Yes vote was the love that dared speak its name, but it was not to be

Despite the result, this is the end of the status quo

Boyd Tonkin on the fall-out from the Scottish referendum
Manolo Blahnik: The high priest of heels talks flats, Englishness, and why he loves Mary Beard

Manolo Blahnik: Flats, Englishness, and Mary Beard

The shoe designer who has been dubbed 'the patron saint of the stiletto'
The Beatles biographer reveals exclusive original manuscripts of some of the best pop songs ever written

Scrambled eggs and LSD

Behind The Beatles' lyrics - thanks to Hunter Davis's original manuscript copies
'Normcore' fashion: Blending in is the new standing out in latest catwalk non-trend

'Normcore': Blending in is the new standing out

Just when fashion was in grave danger of running out of trends, it only went and invented the non-trend. Rebecca Gonsalves investigates
Dance’s new leading ladies fight back: How female vocalists are now writing their own hits

New leading ladies of dance fight back

How female vocalists are now writing their own hits
Mystery of the Ground Zero wedding photo

A shot in the dark

Mystery of the wedding photo from Ground Zero
His life, the universe and everything

His life, the universe and everything

New biography sheds light on comic genius of Douglas Adams
Save us from small screen superheroes

Save us from small screen superheroes

Shows like Agents of S.H.I.E.L.D are little more than marketing tools
Reach for the skies

Reach for the skies

From pools to football pitches, rooftop living is looking up
These are the 12 best hotel spas in the UK

12 best hotel spas in the UK

Some hotels go all out on facilities; others stand out for the sheer quality of treatments
These Iranian-controlled Shia militias used to specialise in killing American soldiers. Now they are fighting Isis, backed up by US airstrikes

Widespread fear of Isis is producing strange bedfellows

Iranian-controlled Shia militias that used to kill American soldiers are now fighting Isis, helped by US airstrikes
Topshop goes part Athena poster, part last spring Prada

Topshop goes part Athena poster, part last spring Prada

Shoppers don't come to Topshop for the unique
How to make a Lego masterpiece

How to make a Lego masterpiece

Toy breaks out of the nursery and heads for the gallery
Meet the ‘Endies’ – city dwellers who are too poor to have fun

Meet the ‘Endies’ – city dwellers who are too poor to have fun

Urbanites are cursed with an acronym pointing to Employed but No Disposable Income or Savings
Paisley’s decision to make peace with IRA enemies might remind the Arabs of Sadat

Ian Paisley’s decision to make peace with his IRA enemies

His Save Ulster from Sodomy campaign would surely have been supported by many a Sunni imam