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In Bird Friendly Cities, key threats to birds are effectively mitigated, and nature is restored so native bird populations can thrive.

Helpful Resources

  • Josh Russell

Cavity Nesting Birds

A Place to Call Home!

Cavity nesting birds use holes in trees or shrubs, called cavities, as their nests. Birds like the Pileated Woodpecker are primary cavity nesters. These birds excavate their own hole in snags (standing dead or dying trees), by hollowing out a dying tree’s inner cavity. In the process of this, these birds provide an essential role in pest control for our community, feeding off many insects (like the Emerald Ash Borer), and aiding in preventing their spread to nearby trees.

Additionally, when they abandon the cavity that they had made, they provide the home for secondary cavity nesters. These birds live in abandoned or natural cavities and include birds like Black-Capped Chickadees. Cavity nesting birds are an essential part of a healthy, diverse ecosystem. Therefore, it is important that we make an effort to help these species in our community. This can be done by:

Selecting the right trees to plant and maintain

White Cedar, Eastern Hemlock, Birch, Aspen, and Sugar Maple trees are native to Peterborough and provide the right type of snags for a variety of primary cavity nesting birds. Different birds however, are drawn to different types of snags. When accommodating the various needs of different cavity nesters, the greater diversity of native trees planted, the better.

Leave standing dead and dying trees alone unless they pose a safety risk

In the past, there has been a tendency to remove dead and dying trees, however, there is a direct relationship between snag abundance and the number of cavity nesting birds in a community. This is primarily due to the fact that fewer snags causes greater inter-competition between cavity nesting birds as well as other species that utilize the cavity, such as mammals like flying squirrels. Therefore, as long as they do not pose a safety risk in our community, an effort should be made to leave all snags standing.

Allowing trees to mature into taller, wider trees

Many species need trees to be a certain height or diameter in order to use them as snags. For example, the Pileated Woodpecker requires snags that are at least 35cm in diameter. To attract these essential species, we need to protect and maintain older trees in the community, in addition to planting new trees.

Planting prickly shrubs to deter predators

Many smaller cavity birds prefer shrubs, like Common Elderberry, Dogwood, and Cranberry bushes, to trees. However, this puts them at a higher risk for predation from threats like neighbourhood cats. Planting shrubs with thorns and trimming your shrubs more often can protect these birds.

Creating suitable and sustainable bird boxes to attract cavity nesters

Due to the decrease in suitable excavation sites for primary cavity nesters, there are fewer available natural cavities for secondary cavity nesters. In place of this, proper bird boxes can be used to supplement natural cavities.

Non-Cavity Nesting Birds

Rather than nesting in cavities, non-cavity nesting birds construct their nests from many different natural materials found in their environment. These can include materials such as grasses, mosses, twigs, and mud. However, due to the amount of litter found in our community, many birds have also started to use anthropogenic materials such as plastic bags, fishing lines, aluminum foil, and cigarette butts in their nests as well. These materials are toxic and are especially dangerous to chicks if accidentally ingested.

In order to protect birds from using these materials, homeowners can leave dead twigs, leaves, dry grass, feathers, moss, bark strip, and pine needles in their backyards to encourage natural nest building.

Note that it is harmful to leave out any non-natural materials like plastics, tinsel, cellophane, aluminum foil, and dryer lint. Please do not provide these materials to any wild animal.

Non-cavity nesting bird species build distinct and unique nests. The most popular types of bird nests include cup nests, woven nests, platform nests, and scrapes.

For help identifying which bird a nest may belong to, visit Nest Watch.

Common types of bird nests

  • Cup nests: Generally made of grasses, twigs, mud, and spider silk. These nests are shaped like a cup, with a large indent in the center that holds the bird's eggs. Oftentimes, these nests can be found in forks of branches and in bushes.

  • Woven nests: Generally made of woven grasses and reeds. They can be found hanging off of tree branches.

  • Platform nests: Generally, made up of many sticks piled upon one another to make a flat nest, softened with the addition of grasses or dirt. These are sometimes found on the tops of trees, or in high vantage points, to give the bird a 360° view of prey.

  • Scrapes: The simplest form of a nest is a scrape nest. The bird scrapes a small indent into the ground and softens it with grasses, leaves, and rocks.

Birds will nest in a variety of locations including in trees, on the ground, in shrubs, on buildings, on telephone poles, and on many other structures. However, there are many advantages for birds that nest on native plants over those that nest on anthropogenic structures. Native plants host a greater number of insects that many birds feed off of. Additionally, birds that nest on anthropogenic structures are at a higher risk of nest destruction due to human interference. For example, a homeowner may need to remove a bird nest if the nest is built in an air vent or if they are repairing a roof on which a bird has nested.

Many times, near a nest, you may come across a baby bird that is on the ground. Before you panic, please consider that the baby may be fledgling and this is a normal life stage for most birds.


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