As I write this I can look out my window and see a busy house sparrow going from the birdfeeder, to the suet feeder, to the blossoms of the pineapple guava bush. The sparrow eats a few sunflower seeds, takes a few pecks from the suet, and then yanks on the sweet fleshy petals of the red and white guava flowers (Feijoa sellowiana).
Bees and other insects seldom visit the guava flowers and they are pollinated almost entirely by birds. As the bird yanks on a petal, the pollen is shaken from the stamens onto the pistil and fertilization takes place. I first noticed this with mocking birds, and then with Hooded Orioles. Today is the first time I've seen a sparrow doing this work. The sparrow may not know it but he (she?) is making sure that I'll have a good crop of guavas this fall.
Just yesterday I was speaking to a group of gardeners about my book, Safe Sex in the Garden. I mentioned how terribly common whitefly-infested hibiscus and Rose of Sharon plants were becoming now in many large cities, especially those with the worst air pollution. The air pollution, largely from the exhaust of all those cars and trucks, stresses and weakens many landscape plants, and this leaves them vulnerable to attack from insect pests.
I explained that when insects such as whitefly, aphids, scale, or mealybugs feast on our ornamental plants, they secrete large amounts of a gooey, nutrient rich substance we euphemistically call "honeydew." On this honeydew dry airborne black mold spores land, stick, germinate, and quickly start to grow. The mold flourishes as long as it has a continuing source of insect-supplied honeydew. Among other things, the dark mold spores on the leaves cut down on the amount of sunlight the plant can receive, and thus further robs the plant of needed food from photosynthesis.
As the mold grows and spreads it turns the infested leaves and stems a fuzzy white or a sooty looking black. The entire effect is one of dirtiness, as indeed it is. The mold quickly reproduces itself by releasing billions of microscopic-sized airborne mold spores. These spores float in the air, we inhale them, and allergy and asthma are the result.
Today there is great interest in indoor toxic mold, and yet outside in far too many of our gardens there is another mold spore epidemic well underway.
I often write and speak about male plants in our gardens and male cloned street trees lining our city streets, and about all the allergenic pollen that these male clones produce. Often overlooked in this discussion is the effect of mold spores from our landscapes. Overlooked even more, is the contribution to our good health from small birds.
Yesterday after my talk, a lady told me that she always feeds the birds in her yard and had done so for many years. She said she feeds them crumbled up small bread crumbs and that some 25 to 30 birds await her every morning. She also said that her own hibiscus plants are thriving, full of flowers, and unlike those of her neighbors, are bug free. "I see the birds eating the whiteflies and aphids from the hibiscus," she said. "I know that they are what is keeping it so clean."
She is completely correct in this assumption, too. I also have seen small birds picking clean an infested bush. One day several years ago, a friend and I sat in his kitchen and watched as a small flock of tiny gray bushtits alighted in the blue mallow shrub next to the window. We knew the bush was loaded with aphids because we'd just been talking about it. As we watched, the little birds jumped from branch to branch, eating aphids. A half hour later when we went outside, the entire bush was aphid clean.
Sometimes you will read that seed-eating birds mostly just eat seeds, but this isn't true at all. Almost all wild birds eat insects. I encourage you to feed the birds, to encourage wild birds in your yard. Not only may they pollinate your guava trees, but they will also help rid your garden of insect pests, all the while making the air you breathe fresher and cleaner.