While many people see snags (dead or dying upright trees) as eyesores that detract from the beautiful natural environment, they should be appreciated for the vital ecological functions they provide for many of our feathered friends. So, three cheers for snags!
Hooray for nesting habitat!
Over eighty species of North American birds nest in cavities of snags. Cavity nesters can be divided into two groups- primary and secondary cavity nesters. Primary cavity nesters are the property developers, as they excavate their own nest cavities. This group includes the Pileated Woodpecker with its characteristic oblong entrance hole and the Hairy and Downy Woodpeckers with their circular entrances. Even though primary cavity nesters can spend up to 6 weeks building their nests, they often do not reuse them, leaving them available for secondary cavity nesters, who nest in cavities but are do not make them. This community is quite diverse ranging from House Wrens to Wood Ducks to American Kestrels to Eastern Bluebirds.
Hooray for roosting habitat!
Winter storms, or even cold nights, can be challenging for birds. Many species seek refuge from the elements by roosting (resting at night) in snag cavities. The warmer microclimate provided by these holes help the bird save critical energy (up to 40%). The savings are even greater if the bird roosts socially with others. Birds regularly select cavities that maximize their energy savings, choosing deep cavities with limited volume, small entrances, and high sun exposure. Furthermore, these cavities also provide roosting birds with some protection from being detected by predators.
Hooray for food!
Many species of insects also make their homes in snags. Beetles and ants, in particular, can become plentiful under the bark of dead and dying trees. This abundance of food attracts species of insectivorous birds in droves, especially woodpeckers. Pileated Woodpeckers, for instance, can spend up to 75% of their foraging time on snags.
Species in Peterborough that you might observe using snags include Black-capped Chickadees, nuthatches, wrens, Tree Swallows, European Starlings, American Kestrels, all of our woodpeckers, many of our owls, and even Turkey Vultures! If you are near water, be on the lookout for Wood Ducks or mergansers coming in and out of their cavity nest!
If you are lucky enough to own property with a snag or two, please consider leaving them standing for your feathered friends. This is particularly important in urban and suburban areas where snags were often removed when the area was developed, and there is a lack of older trees that would have eventually replace them. Lastly, if there are no snags in your area you may consider erecting artificial cavities (nest boxes), while they will not provide foraging habitat, they may provide a safe place for nesting or roosting.
For more information on snags and nest boxes visit: