As I was tending the garden last week, I was interrupted by a loud buzz. I looked up to see a male ruby-throated hummingbird investigating the bird feeders filled with seed. He was obviously looking for his feeder – the one with the sugar-water solution – and, upon not finding it, flew away in what I imagined was disgust. I was caught unprepared again; I thought I had covered all my bases by putting some blooming impatiens out. Nope – he completely ignored them, even though all the books list these among the hummer’s favorite nectar-producing plants.

I used to wonder what hummingbirds do in the absence of feeders and exotic flowers provided by humans. Especially in early spring, when hardly anything is in bloom yet. I had seen them visiting dandelion flowers; I was more surprised when I saw one sipping tree sap that had formed on the stub of a broken branch. But, I theorized, this can’t be a very reliable food source. Although hummers also eat very small insects and spiders, nectar is their primary energy source; without it they’d die within a few hours.

I soon found that hummingbirds have a guaranteed nectar source in early spring when blooming flowers are scarce: sap wells drilled by the yellow-bellied sapsucker. This sap is similar to flower nectar, providing sucrose and amino acids, and attracting many small insects that hummers eat. Researchers call this relationship commensal: one species benefits from another, and neither suffers from the interaction.

Scientists also think ruby-throats time their migration and limit their range to that of sapsuckers, so closely are they dependent on them. Female hummingbirds will even construct their nests near a sapsucker’s sap tree. This makes a lot of sense, because once she mates, the male leaves her to raise the young by herself. She probably couldn’t do this without a ready, reliable source of nectar.

Which brings me to the next topic: putting out hummingbird feeders. There are volumes of information on this topic, some of it hotly contested. I have chosen information gleaned from the University of Maine Cooperative Extension brochure, “Understanding Ruby-Throated Hummingbirds and Enhancing Their Habitat in Maine,” which I paraphrase below.

Recent research indicates that the nectar and sugar-water solutions we concoct are not as nutritious as real nectar. While they may be beneficial to hummers during early spring and early autumn, making feeders available all summer may actually do more harm than good – especially if they are not maintained properly.

Sugar-water solutions can ferment quickly (one to two days) and can harm the birds if consumed. Mold and bacteria also grow quickly in artificial nectar, posing an additional health threat to the birds. It is important, then, to boil the water well (four parts water to one part sugar most closely mimics natural nectar; any unused portions should be refrigerated and discarded after a week), and to keep feeders scrupulously cleaned. Washing them with a drop of dish detergent and disinfecting them with a 10 percent bleach solution (rinsing well and allowing to air dry before refilling) is recommended.

Many people put red dye into their sugar-water solutions, believing it is needed to attract the hummers. Nothing could be further from the truth – I have never added red dye (which some believe may harm the birds) and hummers flock to my feeders. The homemade sugar-water solution described above is also recommended over store-bought nectar mixes, most of which contain red dye.

To view the Cooperative Extension pamphlet on hummingbirds, visit http://www.umext.maine.edu/onlinepubs/htmpubs/7152.htm, or contact UMCE Publications Distribution Center, 5741 Libby Hall, Room 114, Orono, ME 04469-5741. Their phone number is (207) 581-1387. This guide is an excellent source of information on the hummingbird’s life and habitat needs.

The answer to all this feeder maintenance, of course, is to provide plenty of the hummer’s favorite flowers (many of which can be grown in containers) around your property. This is not only healthier for hummers, but enhances your environment as well.

Chris Corio, a volunteer at Fields Pond Audubon Center in Holden, can be reached at fieldspond@juno.com