Restoring Our Birds
October 25th, 2022 by georgann
Canopy: “a suspended covering over a bed, entrance, etc.”, Webster’s Dictionary.
To us it means shelter from rain and snow. To a Scarlet Tanager it means a covered forested hillside or a welcoming neighborhood wooded lot. It means safe foraging for weary migrant warblers on a spring morning. It means a place for tanagers, vireos and warblers to build nests and raise babies.
We have lost much of our canopy in the metro-Atlanta area. Our once-prized continuous cover of crown foliage is disappearing under bulldozers. Large forested lands and small wooded lots are succumbing to urban growth and sprawl. Contiguous forest canopies are now reduced to fragments surrounded by homes and yards. Developers are quick to claim “environmentalism” and proud to call their leftover fragments “greenways”. But are these patches of green large enough to retain the birdlife that once used the larger forests?
Recently a number of studies testing the size of forest fragments have been completed. The research shows that there is a distinct and persistent decline of songbirds in small fragments of forest, of less than 100 acres, despite their composition. No longer are these forests home to neotropical migrants like Hooded Warblers, Black-throated Warblers, and Ovenbirds.
These small fragmented forests have one thing in common. They are surrounded by neighborhoods that have become hostile to them. These neighborhoods contain Brown-headed Cowbirds that parasitize bird nests and many home-owners feed dogs and cats, opossums, raccoons, Blue Jays and Crows that prey upon eggs and nestlings.
Fernbank forest is an example of a small forest that has been severely influenced by hostile development. Thirty years ago, the forest had nesting neotropical species such as Hooded Warblers and Ovenbirds. Today, these birds are missing. They could not raise enough young each year to offset yearly mortality of adults. When a species’ population in the forest declines through natural or unnatural (cowbirds and cats) mortality, only a surplus of birds from another source can keep the population stable. Fernbank Forest, the population sink, has needed to rely upon heavily forested regions, the population sources, to supply it with steady flow of immigrants. Due to development, these population sources have become farther and farther away from Fernbank and the Druid Hills area.
So, do we worry about the size of the forest, its composition or the surrounding landscape? We cannot do much about the size of urban remnant forests, and the houses, shopping malls and highways are hardly going to go away. Can we control the disturbances within the forest itself? Is clear-cutting, logging and loss of canopy as threatening as the development around the forest?
Interestingly, an old-growth forest that has not endured windfalls, fires or logging lacks the variety of bird species found in a diversification of mixed aged vegetation composed of four layers; the ground cover, the herbaceous level, an understory or shrub layer, and finally, the tall canopy. Our forests, wooded lots and surrounding landscapes need to managed to keep their complex diversification necessary for healthy populations of birds
Step outside on a summer day and survey the canopy cover in your neighborhood. An old established neighborhood such as Druid Hills has old towering trees with immense crowns reaching out from tree to tree, even extending across the twisting small streets. Next, inventory the treeless patches such as your house and yard, which have created a canopy gap. As we have seen, this is not so bad as long as you have retained or planted some understory shrubs and trees. If, however, you have extended your gap into a yard of turf with little or no vegetation, then you have added to the loss of bird diversity in the neighborhood.
True, we all can’t live on wooded lots; the developers have seen to that. But we can lessen the devastating impact of endless turf with islands of bird-friendly vegetation. Vary your landscaping by using native plants that are drought-resistant and functional providing seeds, nuts or berries to birds. Choose native trees and shrubs that have varying heights and leaf textures. Plant deciduous and evergreen vegetation.
Try to see your yard through the eyes of a Wood Thrush, a Ruby-throated Hummingbird or a Red-bellied Woodpecker. Remember the canopy is important, but so is the bed under it.
Birding Adventures, Inc.
Georgann Schmalz
Ornithologist
www.birdingadventuresinc.com