A land manager's guide to conserving habitat for forest birds in ...

Photo: Lucas Foerster
6. Retain cavity trees, snags, and downed wood
Cavity trees are living or dead trees that contain holes used by
mammals and birds for nesting, feeding, roosting, or for escape.
Cavities can be excavated by woodpeckers during feeding or
nesting, or created naturally from decay and broken branches.
Over 50 species of birds and mammals in south and central
Ontario rely on cavity trees and snags for food and shelter.
Some, known as secondary cavity users, like Barred Owls,
nuthatches, Wood Ducks, and flying squirrels cannot make
their own cavities. They rely on retention of these natural
holes or old woodpecker cavities for habitat. Even in the
absence of timber extraction, cavity resources can be limited.
As both cavity trees and holes are reused for years by a range
of species, it is important for the land manager to retain them
as wildlife habitat. We recommended you strive to retain at
least 10 living cavity trees greater than 25 cm dbh in each
hectare of forest to provide habitat for cavity dependent
species. Trees should be selected from a range of species,
and with a range of cavity sizes to accommodate the suite of
species. Preference should be given to trees with cavities in
the upper bole, and if possible from tree species that
provide multiple wildlife benefits (e.g., mast producers
and supercanopy trees). Nest cavities in particular are the
most valuable.
Snags and decayed parts of live trees are an important
component of healthy forests. They serve as habitat and a rich
source of food for birds that drill into wood or flake bark to
find insects. This food source may be especially important
during the winter for non-migratory species, when food is
scarce. Snag retention guidelines can be difficult to attain
during harvesting operations, as any trees that are a safety
hazard must be cut down. The retention of a snag may require
a tree length no-cut buffer around it to protect the forest
workers. Ideally managers should leave at least five snags per
hectare, and more where possible. At least one snag and one
cavity tree should be large (greater than 50 cm dbh). Snags
will also become critical habitat in the future, as they fall over
naturally, increasing volumes of decomposing wood.
Downed woody debris (DWD) is not only an important
source of food for birds, but a critical component of the forest
ecosystem, providing habitat for salamanders, reptiles, insects,
bacteria, and fungi, aiding in nutrient cycling, and creating
structural diversity important for the regeneration of many
tree and plant species. In addition to an overall reduction in
the volume of DWD in managed stands, there is a shift
Female Wood Duck at cavity nest — Photo: Jeff Nadler
Snag — Photo: OMNR
Guidelines for Forest Management and Maintenance of Forest Bird Diversity 67