By Terry W. Johnson
The plight of neotropical migratory birds is well documented. These are the birds that nest throughout North America and winter in Latin America, a kaleidoscope of birds including orioles, warblers, vireos, thrushes, tanagers and other colorful songsters. The fact that many of them are suffering frightening population declines is a major concern for conservationists.
Biologists were once of the opinion that habitat losses on winter and breeding grounds were the most serious threat faced by many of these birds. However, research conducted during the past two-and-a-half decades suggests that a dramatic loss in suitable stopover areas used by the birds on their spring and fall migrations is also playing a significant role in their alarming population losses.
Believe it or not our yards can help in conserving these migratory songbirds by providing high-quality stopover areas.
Stopover areas are simply places where birds can pause on migration, to rest and refuel before continuing their journey. They are, in a way, much like the gas stations and restaurants we visit on a trip to Disney World or other distant destination.
The best stopover areas for fall migrants contain abundant fat-rich berries and fruits and, to a lesser extent, insects. Migratory birds will remain at these pit stops anywhere from a day to weeks before moving on. How long the stay is often dictated by weather and how much food is available.
While a few species fly nonstop from where they breed to wintering grounds, most make a number of stops along their migratory pathway. It is estimated that an average songbird stops every 165 miles during its south-bound migration. Consequently, these migrants depend on the availability of these feeding and resting sites before they reach the southeastern United States' coastline. From there they must fly nonstop at least 500 miles before making landfall.
The fuel that powers their migration is fat. Fat accounts for up to 50 percent of the weight of long-distance migrants. Birds that are unable to accumulate enough fat prior to and during migration fall into the warm waters of the Gulf of Mexico and perish. It is estimated that half of all fall migrants fail to return to North America the next spring.
Many of the songbirds that make this epic journey are primarily insect eaters. However, an amazing thing happens just prior to migration. As summer days become increasingly shorter, many long-distance migrants drastically switch their diet to include high-fat berries and fruits. In one study, the majority of the 69 insect-eating species studied made the switch. Fruits and berries made up to 80 percent of their diets as they prepared for the fall migration.
A few of these that birds make this dramatic dietary switch are tree swallows, red-eyed vireos, scarlet tanagers, yellow-rumped warblers and Baltimore orioles. The birds that are most successful in storing fat are those that eat a combination of fat-rich berries and fruits as well as insects. Interestingly, in the case of some species, the birds that eat the most berries and fruit show the greatest weight gains.
Biologists theorize that there are many advantages to making this dietary switch. Since fruits and berries often are found in great abundance in a relatively small area, fall migrants are able to spend less time and energy searching for them than they would trying to catch insects. Additionally, birds that dine on fruits and berries suspended from branches in dense shrubs and trees are less likely to be caught by hawks and other predators than they would if chasing down insects in the open.
Biologists have discovered that small areas, even as small as a typical backyard, are vitally important pit stops only if they provide a cornucopia of fruits, berries and insects. The problem is even small high-quality pit stops are in short supply. Sadly, with urban sprawl and other land uses gobbling up more wild habitats each day, this problem will only get worse. With that in mind, one of the best ways that we can personally offer a much-needed helping hand to these migratory songsters is to transform our own yards into high quality stopover areas.
If you are interested in taking on this task, the first thing you need to do is take a close look at your yard. Check for the presence of woody vines, shrubs and trees that bear fruit and berries from August through October. If you find that these plants are missing or in short supply, begin planting them this fall.
Before you begin, take a page from Mother Nature's guide to landscape design. By that I mean that the next time you visit a healthy forest, take note of the fact that the forest consists of distinct layers of vegetation. The limbs and foliage of the tallest trees form a large umbrella over the forest. Below that will be a layer of much shorter trees that form what is called a mid-story. Saplings and shrubs grow in a level below the mid-story. Finally the layer closest to the ground is blanketed in grasses, forbs and other herbaceous plants.
If you were to study the feeding habits of birds that inhabit forests you would learn that different species of birds prefer to feed at different levels. Consequently, when planting fruit- and berry-producing plants, try to create as many of these levels as possible.
Woody vines that produce fat-rich berries such as Virginia creeper can provide food across all levels.
Also, whenever possible, use native plants in your landscape. These plants have co-evolved with the songbirds that migrate through Georgia. As such, they often bear fruit when the migrants are passing through. It is also wise to select plant varieties that grow best in your part of the state.
Here is a short list of some of the plants that will help your yard become a valuable fall songbird stopover site:
Wax myrtle: Wax myrtle berries are gobbled up in large quantities by fall migrants varying from tree swallows and yellow-rumped warblers to scarlet tanagers. This plant is especially important along the coast where wax myrtle thickets are rapidly being lost to development. Wax myrtle is tolerant to a wide range of habitat conditions, including salt spray.
Black gum: This tree produces 1/4-inch purple fruits. The berries are produced only on female plants. Although black gum is often overlooked, it is a valuable fall and winter food plant for a wide variety of wildlife.
Dogwood: Dogwood berries are relished by migrating songbirds and other wildlife. A number of varieties are available at nurseries specializing in native plants.
Hawthorn: Hundreds of varieties of hawthorns grow in the wild and a number of cultivars have also been developed. One of the most popular varieties is parsley hawthorn. Hawthorn fruits persist well into winter.
Hackberry: This tree produces dark red to purple fruits from September to October, and the fruits persist on the tree into February. At least 47 species of birds feed on hackberry fruit.
American beautyberry: The bright purple fruit of this plant attracts species such as catbird, wood thrush, northern mockingbird and American robin.
Crabapple: Select varieties that bear fruits ranging in diameter from a 1/4 to 3/8 of an inch. The fruits of some varieties persist throughout the winter. Crabapples are eaten by gray catbirds, mockingbirds and others.
Virginia creeper: This woody vine provides both attractive foliage and berries that birds relish. The fruit is consumed by great-crested flycatchers, red-eyed vireos, bay-breasted warblers, eastern kingbirds, tree swallows, hermit thrushes and others.
Pokeberry: The dark purple berries of this native perennial are eaten by eastern kingbirds, summer tanagers, hermit, Swainson's and wood thrushes, as well as hooded warblers and great-crested flycatchers.
Spicebush: The red berries of this native begin ripening in summer. They are a choice food of thrushes, red-eyed vireos and others.
Viburnum: The deep-blue berries of this native shrub are favorites of a number of birds including the hermit thrush.
Sumac: Sumac berries are consumed by gray catbirds, Baltimore orioles and scarlet tanagers, among others.
Elderberry: The berries of this plant are gobbled up by yellow-breasted chats, veeries, wood thrushes and others.
The list of plants that bear valuable fall berries and fruits also includes hollies, red cedar and Carolina snailseed.
If you are trying to create a great fall stopover area, one of your goals should be to offer birds with the greatest variety of food possible. This will ensure that some food will be available throughout late-summer and fall even when a particular plant doesn't produce well.
If you do decide to begin creating the ideal migratory songbird pit stop, don't try to do it all at one time. Plant a few berry and fruit-producing plants at a time. In that way you don't become overwhelmed with the job.
Another thing to keep in mind is that the size of your yard will dictate what you can plant. Some yards are simply too small to plant large trees such as hackberries. If you only have room for small trees and shrubs, plant those.
Once your plantings begin producing crops of fruits and berries, you will be amazed at the diversity of fall migrants that will drop in to dine just outside your backdoor.
Terry W. Johnson is a former Nongame program manager with the Wildlife Resources Division, a backyard wildlife expert, and executive director of TERN, the friends group of the Nongame Conservation Section. (Permission is required to reprint this column. Contact firstname.lastname@example.org.) Learn more about TERN, The Environmental Resources Network, at http://tern.homestead.com. “Out My Backdoor” columns archive.
The plight of neotropical migratory birds is well documented.