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

Male Black-throated Blue Warbler
— Photo: Garth McElroy
cooler temperatures created by the shading effect of the overstorey canopy. Woody
perennial plants (trees and shrubs) dominate the intermediate storey.
3. Understorey: includes the lowest vegetation layer such as mosses, ferns, grasses, small
wildflowers, and other low ground covering herbaceous or woody plants (shrubs and
tree seedlings).
Immediately following clear cutting or farmland abandonment, the bare land will begin
to support patches of herbaceous vegetation such as grasses and forbs. This habitat will be
suitable for grassland species like Eastern Meadowlark and Bobolink. As succession
advances, woody shrubs, seedlings, and saplings invade the area, providing habitat for
species like Gray Catbirds and Eastern Towhees. Early and mid-successional forests may
have two layers, an understorey of shrubs and young trees, and an overstorey of canopy
trees. Once the overstorey tree canopies become interlocking, the forest floor is typically
bare until canopy trees are taller and natural mortality or human intervention creates gaps
where light can reach the forest floor. Within late-successional or old growth forests,
structural diversity is usually high, there are extensive patches of dense herbaceous ground
cover, and understorey of seedlings and shrubs, intermediate layers of saplings and small
trees, a lower canopy of small trees, and a primary canopy of mature trees.
Overall, the age structure of forests within our human dominated landscape has shifted
towards younger forests, at the expense of species dependent on mature forest conditions.
Land managers can use management techniques to encourage old growth features and
pockets of high structural diversity. They should make an effort to preserve existing old
growth stands and provide for the development of future old growth stands by leaving areas
undisturbed or unharvested for 150 years or more. Controlling ungulates, particularly whitetailed
deer or grazing cattle, monitoring and controlling invasive plants and human
recreational activities may be necessary to protect understorey vegetation and sensitive
habitats in some areas.
Landbird Migration
Stop-Over Areas
Forests provide birds with food, water, and
cover, not only during the breeding season
but for some, throughout the year, and for
others, at critical stages during migration.
Stopover habitats are essential to successful
bird migrations. Migrating birds need these
critical stopover locations in the same way
we need gas stations, restaurants, hotels,
and rest areas when we take long trips.
Strategically located patches of woods,
wetlands, and other natural habitats with
adequate food and shelter ensure the
survival of a species. If development
continues to remove these habitats from
our landscape, it becomes increasingly
difficult for exhausted migrants to find
suitable areas to rest and refuel. Large
numbers of migrating birds move along the
shorelines of the Great Lakes, stopping to
rest, feed, and/or wait for inclement
weather to pass before attempting to cross
open water. Because each species has
different habitat requirements, they require
a variety of relatively undisturbed habitat
types, ranging from open fields to mature
forests. In particular, forested habitats within
5 km of the Great Lakes (especially Lake
Erie and Lake Ontario) provide roosting
areas, cover from predators and foul
weather, and food for large numbers of
migratory birds. Landowners and managers
can help protect important migratory
stopover areas by using restoration and
silvicultural approaches that maintain
forested land, especially along
watercourses and in areas where little
woodland remains. As a general rule, like
breeding birds, managing forests for habitat
diversity is good for migrating birds.
Diverse, mature forests with shrub and
sapling layers will provide a high diversity of
edible fruits and nuts in the fall that allow
migrants to replenish their resources prior
to the next leg of their journey.
Regenerating field — Photo: Harold Lee
Forest Birds in Ontario 19