| Birds are the true architects of the natural world. | | | | also for the adults who are sitting on them. It |
| Not only do they design fascinating and | | | | usually takes several weeks for the eggs to |
| complicated structures, the variety of materials | | | | hatch so it's critical they remain hidden from |
| used is absolutely amazing. From tree cavities to | | | | predators and protected from the elements. Nest |
| cliff banks to simple platforms birds utilize any | | | | structure often provides insulating properties, |
| sort of natural substance they can maneuver with | | | | either by the materials used - such as feathers - |
| beak or foot. They're not above making use of | | | | or the nest location with respect to prevailing |
| man-made structures or objects either, which is | | | | winds and sun exposure. |
| why it is so easy to enhance your bird watching | | | | Nest Materials |
| activities simply by providing a properly designed | | | | When it comes to nest building, we think of grass, |
| bird house or some dog hair, then watching them | | | | mud, feathers, and twigs, as mentioned in several |
| go to work. | | | | of the above nest types. Indeed, all of these are |
| The act of nest building is triggered by hormones. | | | | common 'fabrics' in nest architecture. We could |
| Other factors such as migration, day length, food | | | | add to that list what may seem like strange |
| availability, and territoriality also contribute, though | | | | items: guano, spider web, snake skin, shells, saliva, |
| such behaviors are themselves subject to | | | | fur, even human artifacts such as string, plastic, |
| hormonal influence. The reproductive organs of | | | | buttons, shoelaces, and jewelry! Each of these |
| birds are significantly reduced in size for most of | | | | has a purpose, believe it or not. For example, |
| the year, an adaptive strategy so they have less | | | | manure helps disguise the scent of nestlings, |
| weight to carry in flight. Once hormones kick in, a | | | | thereby fooling predators. (Look up references on |
| male's testes and a female's ovaries increase in | | | | burrowing owls!) Saliva acts as a super-glue. Insect |
| size enormously. On post-mortem examination, it | | | | and spider silk add tensile strength and can also |
| is simple to tell the reproductive status of a bird | | | | repel rain. Nuthatches smear pitch around the |
| simply by checking the size of these organs. Once | | | | entry hole of their nest and then rub ants in the |
| the breeding season is over, ovaries and testes | | | | pitch; the combination is both a both a chemical |
| shrink back to tiny little structures located ventral | | | | and a mechanical deterrent to ward off |
| to their kidneys. | | | | marauders. |
| Nest types | | | | If that weren't enough, it is not uncommon for a |
| Most people are familiar with the size and shape | | | | bird to deliberately build near a colony of bees or |
| of a robin's nest which is a mud and grass | | | | wasps, a truly ingenious way to keep parasites |
| structure often found in our yards or even built | | | | like botflies and warbles away. |
| over the porch light on the front steps! But there | | | | The Construction Process |
| are many other types of nests made with a host | | | | So how complicated is it to be a bird 'contractor'? |
| of innovative materials. Here are a few examples | | | | Some species are so lazy, they prefer not to |
| of nests you may find when you're out exploring. | | | | build at all and simply take over a previously built |
| - Cavity nests: Created in trees by woodpeckers | | | | nest masterminded by another species in a |
| or natural weathering, tree cavities make homes | | | | previous year. The great horned owl is a class |
| for many species, including tree swallows, | | | | example. This species often uses old magpie, |
| woodpeckers, nuthatches, chickadees, house | | | | crow, or hawk nests, adding a new twig or two |
| wrens, bluebirds, wood ducks, saw whet owls and | | | | and being quite satisfied with that. Several species |
| many more. Some birds may even build a nest | | | | of shorebird use little more than a slight |
| where they find the 'artificial' cavities in human | | | | depression in natural substrate, camouflaged by |
| structures, such as stove vents, dryer vents, | | | | rocks, earth, and vegetation. Other species have |
| chimneys, eaves, soffit, and under shingles. The | | | | such complicated nests they literally need to |
| classic bird house, manufactured by humans in a | | | | make over a thousand trips back and forth, |
| variety of shapes and styles, caters to many | | | | carrying needed materials. |
| cavity nesters. | | | | In most cases, a new nest is built each year |
| - Cups: Commonly seen on ledges or in the crook | | | | though a few species will return to the same nest |
| of a branch, a nest cup is usually a woven circular | | | | year after year, adding materials and making |
| bowl made from grass, leaves, string, hair, and | | | | repairs to any damage that may have occurred |
| mud or saliva to help hold it together. Many | | | | over the winter. |
| species make this type of nest, such as | | | | A newly constructed nest is beneficial for several |
| blackbirds, goldfinches, robins and barn swallows. | | | | reasons. Firstly, nests need only last a short time |
| The two latter species may build their nest cups | | | | as the entire time-line from egg-laying to fledging |
| on an artificial nest platform secured to the side | | | | may be as little as six weeks so it is |
| of your house or garage. | | | | counterproductive to spend a lot of time and |
| - Hanging baskets: The colourful Baltimore oriole | | | | energy on something that is required temporarily. |
| makes a delicate grass basket that hangs from a | | | | Secondly, avian parasites can accumulate in the |
| branch and sways in the wind, looking for all the | | | | nest materials, then persist over winter so when |
| world as if it will fall apart in a mild storm. | | | | the nesting pair returns in the Spring, there may |
| However, orioles aren't the only ones who weave | | | | be enough parasites to pose a serious health risk |
| baskets. Other species like the bushtit also weave | | | | to nestlings, perhaps even contributing to their |
| baskets, using moss, hair, and plant fibers. | | | | mortality. |
| - Mud tubes: Who hasn't seen the amazing globular | | | | Conversely, making simple modifications to an |
| nests of cliff swallows? It takes hundreds of trips | | | | existing nest, rather than starting from scratch, |
| from the mud source to the bridge, building, or | | | | saves time and energy, resources that are |
| cliff wall that is host to a cliff swallow's tubular | | | | priceless to almost all birds. |
| nest. Each little mud ball is mixed with saliva to | | | | To maximize efficiency, birds tend to build |
| create enough sticking power to hold it all | | | | relatively small nests. Again, temporary |
| together. | | | | accommodations do not need to be large. |
| - Platforms: Gathering branches, twigs, grass, | | | | Another advantage of a small nest is the ability to |
| (even green herbs), into a rather untidy mass, | | | | hide it from predators more easily. Perhaps the |
| many raptors build their nests on top of a | | | | most important reason for a small nest relates to |
| supportive platform, using both natural and | | | | the super-speedy rate at which nestlings grow |
| man-made foundations. Some are relatively small | | | | into fully-flighted juveniles. Imagine developing |
| and inconspicuous, hidden from potential predators. | | | | from a new-born baby to an Olympic caliber |
| Cooper's hawks and sharp shinned hawks are | | | | athlete in just six to ten weeks! The nutrition |
| likely to build these. Others are huge in both size | | | | required to accomplish this is astounding but even |
| and stature, like those made by osprey and | | | | the best nutrition is not enough without adequate |
| eagles. Adding materials year after year, both | | | | leg support for maturing birds. As a nestling |
| ospreys and eagles can accumulate hundreds of | | | | grows, it must keep its legs firmly tucked |
| pounds worth of nest material that increase in | | | | beneath its body or the legs grow sideways, in a |
| size, perhaps reaching 7 feet across and as many | | | | splayed-leg fashion that is ultimately fatal. |
| feet deep. One nest was known to weigh well | | | | Therefore, the close proximity attained in a |
| over a ton when it finally collapsed. Platform nests | | | | crowded nest ensures that won't happen. |
| may be located atop an old magpie nest, in a | | | | Bird Nests and the Law |
| sturdy tree, on a cliff edge, or on a man-made | | | | The vast majority of bird species in North |
| structure such as a power pole, a bridge, or an | | | | America are protected by an International treaty |
| artificial nest platform. The green plants added | | | | known as the Migratory Bird Treaty Act. This |
| each year are known to contain natural repellents | | | | protection is extended to their nests and all of its |
| that help ward off insects and parasites. | | | | occupants. It is against the law to harm, move, or |
| - Tunnels: Kingfishers and puffins, two species | | | | harass nesting birds. If a bird builds its nest in a |
| that feed on fish, gouge out tunnels in dirt banks | | | | location that may be dangerous or inconvenient to |
| or on cliff edges overlooking their favourite | | | | a homeowner, they must obtain permission from |
| hunting zones. Burrowing owls will use the | | | | their local and/or federal wildlife authorities in order |
| pre-made tunnels created by rodents such as | | | | to remove it. The wisest choice is generally to |
| Richardson's ground squirrels. | | | | leave it where it is; it is not difficult to co-exist |
| - Ground: Many species hide their nests | | | | peacefully with most species. Keep in mind how |
| somewhere on the ground, sometimes protected | | | | short the nesting season is and how enjoyable it |
| by a low-growing bush, sometimes protected only | | | | can be to watch the labour-intensive process of |
| by the fantastic camouflage of the substrate | | | | rearing baby birds until that momentous day when |
| itself. Shorebirds, ducks, and a lot of songbirds | | | | the fledglings venture out of the nest for the first |
| build this type of nest. Even some birds of prey | | | | time! |
| will nest on the ground, such as short eared owls, | | | | If you think nest building is fascinating, the |
| snowy owls, and ferruginous hawks. These | | | | intricacies of egg-laying will blow your mind! Watch |
| raptors have evolved in areas where they may | | | | for a future article on this subject, as well as a |
| not see a tree for weeks on end, so they have | | | | fistful of other cool topics on wild birds and |
| adapted accordingly. The main purpose of a nest | | | | mammals. |
| is to hold eggs while they are incubating. This is a | | | | All rights reserved. |
| very vulnerable time, not only for the eggs but | | | | |