Lorraine Julien | Jun 05, 2013


by Lorraine Julien


Birds are among the world’s most skilful nest builders. Few other creatures exhibit such a variety of architecture or materials. Many birds place their nests inside shelters (My brother is wishing he’d covered a section of aluminum soffit on his cottage now that a Robin has built a nest there. It’s great for the Robin but kind of messy on the deck and steps!)

Usually the male selects a good location and then the female does most of the actual nest building. Each different species has its own unique nest-building technique and constructs the structures without ever getting confused. Kingfishers, for example, burrow in riverbanks, Woodpeckers drill cavities in trees; other birds use natural tree hollows or birdhouses. When small family farms were prevalent with lots of old barns, Barn swallows seemed to be everywhere. Now, partly because of this lack of habitat, their numbers are dwindling like so many other insectivores. Most birds, however, construct nests in the open – on the ground or among the branches of trees and bushes.

The simplest type of nest is none at all! Some birds do not build nests but are choosy about the nest site. Some just “scrape” the ground then lay eggs directly on the ground or on trampled vegetation such as the Short-eared owl. Nightjars do not even make a scrape. Two eggs are laid directly on the ground. If you’re walking near a farmer’s field you may startle a pair of Bobolinks. Unfortunately, they make nests directly on the ground, quite often in a cornfield that is soon ready to be plowed or a hay field that will soon be cut. Obviously the nests are very susceptible to destruction by farm equipment. Bobolinks are now classified as “threatened” under Ontario’s Endangered Species Act, 2007. Since the eggs are laid in late May and early July, it forces farmers to avoid growing and rotating certain crops.

The Hummingbird nest can be a tiny, exquisite bowl fashioned from lichens and plant down fastened with spider silk about 10 to 30 feet above the forest floor. Hummingbirds lay the smallest eggs – usually two pea-sized eggs are laid in the nest cup. Cliff swallows make neat bottle-shaped homes of mud plastered against walls. Some birds of prey such as Osprey, Eagles and Herons, construct stick nests eight or ten feet wide and deep with a depression in the middle.

When the parent birds leave the nest in a search for food, their offspring are completely defenceless. Their nests are concealed with great skill in treetops, holes in trees and cliffs, or even in tall grass, and provide a safe, hidden shelter for the chicklets. We’ve all seen Crows being chased by little birds, probably after the Crows had eaten their young.

Nests also provide protection from the cold. Since birds are hatched featherless, and since their muscles do not get any exercise within the egg, they are relatively immobile and need warm, cozy nests to insulate them from the cold. Scientists believe that all birds once laid white eggs, as their reptilian ancestors did. Colour and markings gradually evolved as protective camouflage.

Robins build their nests from dried grass fibres and small twigs. After a soaking rain, they take a beak full of mud back and forth to the nest site a few hundred times. The grasses are woven together, cementing them to each other and to the supporting branch or windowsill with mud. The mud acts as an adhesive but also prevents cracks from developing. Next, the nest is shaped into a perfect baby cradle lined with the softest grasses and hairs they can find. When mud is used in nest building, the birds usually select a location under an overhanging cliff or man-made structure to prevent rain from softening and destroying the nest.

The Goldfinch nest is an open cup of small root and plant fibres lined with plant down, often woven so tightly it can hold water. The nest is lashed to supporting branches using spider silk. It takes on average about six days of non-stop work before the nest is finished. It’s often built high in a shrub where two or three vertical branches join, usually shaded by overhanging leaves or needles. Goldfinches wait until June or July to build their nests once milkweed, thistle and dandelions have produced the seeds they need to feed their young.

Most birds are hard at work building their nests but an exception is the Brown-headed Cowbird. It’s so lazy that it lays its eggs in the nests of other birds leaving the eggs to be hatched and raised by another species of bird. This sometimes works but, in the case of the Goldfinch, the Cowbird babies only live for two or three days as they can’t survive on the all-seed diet of the Goldfinch.

I couldn’t finish this column without mentioning a human example of a bird nest design. Remember the 2008 Summer Olympics and Paralympics in Beijing, China? The Beijing National Stadium was known as the Bird Nest Stadium because of the design of its steel beams and the bird nest shape.

I’ve barely scratched the surface here on the various types of bird nests and their construction by the spectacular birds that build them. 


 

Please feel free to report any observations to Lorraine Julien at This email address is being protected from spambots. You need JavaScript enabled to view it.  or Steve Blight at This email address is being protected from spambots. You need JavaScript enabled to view it.

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