Wild Ideas: Songbirds turn to soft mast as food options dwindle  

This time of year, a lot of berries and other fruits of wild plants start looking pretty dodgy, but for some wildlife they are critical to surviving winter.

Flying insects are still appearing during warm spells and will likely do so throughout the winter. Even as days get colder, insect larvae will still be available, but mostly in and under logs, under detritus on the forest floor or in the mud along streams. While winter wrens, woodpeckers and some other birds are equipped to go after these hidden treasures, other birds are not. By early November, I was already seeing some songbirds that have arrived for the winter or were migrating through turn to another option — soft mast. Mast is the fruit of plants that wildlife eat. Soft mast includes grapes and and berries, while hard mast consists of nuts.

Every year since 1992, the Virginia Department of Game and Inland Fisheries (VDGIF) has joined with the Virginia Department of Forestry (VDOF) to survey hard mast from oak and beech trees, and soft mast from greenbrier, grape vines and dogwood, cherry and gum trees, which are only a few of the species that produce fruit that is available after the growing season ends. These surveys help VDGIF assess changes in deer, bear and wild turkey harvests and provide information to hunters and outdoor writers as they prepare for the hunting seasons, according to Gary Norman, VDGIF’s Forest Game Bird Project leader and coordinator of the joint mast survey.

The survey is conducted on public lands managed by VDGIF and the U.S. Fish and Wildlife Service. Norman also coordinates an eight-state regional survey, and is co-coordinator for VDGIF’s annual acorn survey (look for more on this in an upcoming column).

“I started the DOF survey with hopes of increasing our knowledge of annual production in the Piedmont and Tidewater areas,” Norman wrote in a recent email. He asked foresters to inspect the species he listed for the survey in August and “then at the end of the period report their impression of county-wide production.”

This year, the survey was conducted in 37 counties, mostly in the Piedmont and Blue Ridge physiographic provinces, where most state lands are located, but the other provinces were also included. Norman reports the soft-mast results were good across the commonwealth this year. All species surveyed yielded crops at or above their long-term averages except cherry, which was only slightly below its average.

Where I live, frost grapes (Vitus vulpina) — also known as winter grape, fox grape or wild grape — are plentiful. The vines grow up many of the trees along the forest edge here, including those in the copse near my deck, so I get to see who is eating the fruit and when. While the fruit is usually high in the trees, I do occasionally find branches with grapes lying on the ground. Dark purple at their peak, these grapes turn black and shrivel as they age. As with some commercial grapes that are used for dessert wine, a touch of frost helps concentrate the sugar in them, providing an energy boost for their consumers and making them one of the favorite fall fruits for many species of wildlife.

While I’ve seen fruit-eating birds, such as cardinals and cedar waxwings, dine on frost grapes regularly, I’ve also seen sparrows, pileated woodpeckers and squirrels picking them off the vines. On Nov. 8, I added the American robin to the list. The most common explanations as to why robins are increasingly overwintering this far north are global warming and the availability of fruits from honeysuckle or other nonnative ornamental plants used for landscaping. Apparently native grapes also help fill that role.

Another wild fruit that becomes more appealing to wildlife as other options dwindle is the pokeberry. The day after seeing the robin, the weather turned miserable — dark, cold and rainy. Despite the dank day, the birds that inhabit the shrubbery around the yard this time of year were out foraging, undaunted. I was also out, playing Frisbee with my dog.

Pokeberries, even when shriveled and black in fall, are eaten by a wide variety of wildlife. By Pam Owen

I caught a glimpse of a bird landing on a pokeweed a few feet away. It flitted too quickly among the branches in the pokeweed and a hydrangea nearby for me to identify it, eventually taking off. I at least did confirm it was eating the pokeberries, which by this time of the year are as shriveled and black as the frost grapes but are still eaten by many wildlife species.

Hawthorn berries are also eaten by a range of birds, especially in winter, particularly waxwings and thrushes (such as robins). However, I’ve yet to see any birds go after the berries growing on a hawthorn tree in the same garden as the pokeweed. These round berries, a bit bigger than pokeberries, stay bright red through most of the fall but start to turn dark and leathery by late November. Although they look better than the other choices to me, and are known to be sweet and mild at their peak by people who forage for them, I’m no bird. I’ll keep checking the berries as fall progresses, to see if they have any takers.

Hawthorn berries keep their bright red color through most of the fall and are eaten by thrushes, such as robins, and cedar waxwings. By Pam Owen

We only have a few dogwoods here, and they didn’t exactly produce a bumper crop this year. As Norman explains, the volume of mast produced by a plant species can vary from place to place.

The next sunny day, I took my camera and the longest lens I have (a 75-300 mm zoom) and walked a few yards into the forest above my house. A stream near the trail usually attracts a lot of birds that migrate here to spend the winter, including ruby-crowned kinglets and winter wrens. I couldn’t find either species, but I did spot a northern cardinal and a hermit thrush feeding on frost grapes high in a tree. With the distance, clutter of branches and inadequacy of my lens, I got subpar shots, but at least I could confirm both bird species were indeed eating the grapes.

In November, a hermit thrush leaves its usual habitat nearer the forest floor to feed on frost grapes high in a tree. By Pam Owen
Frosts concentrate the sugar in frost grapes, which are popular with many songbirds and other wildlife. By Pam Owen

© 2018 Pam Owen

Pam Owen
About Pam Owen 343 Articles
Writer, editor, photographer, and passionate nature conservationist living in Rappahannock County, in the Blue Ridge Mountains of Virginia. Two favorite quotes: By E.O. Wilson, who coined the term "biodiversity," "Nature holds the key to our aesthetic, intellectual, cognitive and even spiritual satisfaction”; by Douglas Adams, “I love deadlines. I love the whooshing sound they make as they pass by.”