August 20, 2011
THERE'S NOTHING LIKE the fluttering of tiny bird wings to enliven a garden. From their visual and auditory delight to their comic antics and familial behavior, these entertainers can inject a wonderful dimension to the garden. That's in addition to their role as predators, helping to keep down pest populations by feasting on harmful insects and weed seeds.
They can, however, become pests when they damage or consume our fruits and vegetables, build nests in our buildings or just plain hang around and leave their droppings behind. While overall they provide a greater benefit than detriment to home gardeners, too much of a good thing may turn into trouble — especially as you're about to harvest summer fruits or plant your fall vegetable garden. A number of our feathered friends can wreak havoc with food crops.
Knowing the favored foods of problematic birds and the time of year they are most likely to do their damage can help you effectively manage them.
Petite white-crowned sparrows (Zonotrichia leucophrys) with their distinctive black-and-white head and crisp gray breast love lettuce, grapes, strawberries and melons. House finches and house sparrows are frequent visitors to backyard feeders. The gregarious small-bodied house finch (Carpodacus mexicanus) has a fairly large beak; adult males are rosy red around the face, upper breast and rump. The slightly smaller, chunkier house sparrow (Passer domesticus) looks different from other sparrows; males are brightly colored with gray heads, white cheeks, a black bib and rufous neck. Both of these year-round residents are primarily seed-eaters; as they search for food, they unearth newly planted and sprouted seeds. They can also disbud and deflower fruit and nut trees reducing overall production.
Stocky, broad-shouldered blackbirds (Agelaius species) and boisterous European starlings (Sturnus vulgaris) are notorious for attacking lettuce and cabbage-family transplants, sometimes reducing leaves to ribbons. Blackbirds also love peppers, tomatoes and sweet corn, whereas grapes, cherries and strawberries can be wiped out by a flock of the iridescent purplish-black starlings.
Corn and sunflowers are favorites of the assertive blue and gray Western scrub jay (Aphelocoma coerulescens) and the coal-black crow (Corvus brachyrhynchos). Both of these wily critters can supposedly spot seedlings just as they emerge and tear them out to eat the tasty treat at the base. In addition, the ubiquitous common crow can make a mess — they're excellent problem-solvers capable of figuring out ways to raid garbage cans and discarded food containers.
Bird damage is usually most severe where birds find refuge, build nests or have other sources of food available. Modifying their habitat is a first step to managing annoying birds. By observing their activity, you may be able to identify changes to the garden that makes it less desirable to them like thinning branches of shade trees to discourage nighttime roosting of blackbirds, starlings and crows, or pruning shrubs to reduce protective cover for some smaller types of birds. If you feed wild birds and have problems with some of those same species, it may be time to reassess which birds you feed and/or what kind of feed you provide.
Exclusion techniques are generally easy to use, effective and support a bird-friendly environment. Well-placed bird netting, ¼- to ½-inch mesh plastic, can prevent or discourage most birds from causing damage to edible plants. To protect young seedlings, lay the mesh loosely over the top of the bed, providing support where seedlings are very delicate. Edges of the netting should touch the ground and be weighed down with a few stones. For raised beds, the netting should hang over the edges of the bed. If you have just a few young plants to protect, cover each with an inverted strawberry basket.
Where feasible, protect fruit trees by attaching netting to a frame to hold it away from the tree so that birds can't get to fruit at the outer edges of the tree canopy. You can also drape netting over the fruit tree and close it around the trunk to avoid trapping birds inside. Keep jays and crows away from your corn and sunflower seeds by planting in shallow trenches covered with an arch of chicken wire; leave the wire in place until the tips of the seedlings touch it, then remove the wire.
Scare tactics are another method of reducing nuisance birds, though their effectiveness may be short-lived, especially when dealing with crafty birds like crows. Birds generally don't like anything shiny or that moves; attaching streamers of reflective tape directly to fruit trees, hanging old CDs or pie plates from a fence or post near your berry patch, may dissuade birds from attacking ripening fruit. Frightening birds with a perceived predator (like a scarecrow or inflatable faux owl or snake) requires moving it to a new position every few days; birds will likely figure out it really isn't a threat and resume feasting on your crops.
A blast from an air rifle might scare a flock of crows away, but be warned not to aim at a bird; all wild birds except European starlings, house sparrows and common pigeons (aka "rock dove") are protected by U.S. law. The Migratory Bird Treaty Act of 1918, one of the country's earliest environmental laws, bans the "taking" of any native birds. "Taking" can mean killing a wild bird or possessing parts of a wild bird, including feathers, nests, or eggs.
Our feathered friends add so much to the garden; with a little careful observation and planning, you can have your cake (or apple or tomato) and eat it, too, by planting enough for you and the birds. The birds get their share, you get yours, it's not much extra work, and you'll reap the myriad benefits birds provide.
The University of California Marin Master Gardeners are sponsored by UC Cooperative Extension. For questions about gardening, plant pests or diseases, call 499-4204 from 9 a.m. to noon, and 1 to 4 p.m. weekdays, or bring in samples or pictures to 1682 Novato Blvd., Suite 150B, Novato.
For more information on identifying birds, go to the Cornell Lab of Ornithology at www.birds.cornell.edu.