(Editor's Note: The writer is an associate professor of sociology at Adelphi University and a Woodbury Resident.)

You don't have to go to birding hot spots like Costa Rica or the Galápagos Islands to encounter the mystery of birds. They literally may be right outside your door as I discovered this spring.

Mystery #1. Who's That Knocking at My Door? One cool gray afternoon there was a persistent tapping sound coming from outside, on or near our front door. My wife and I looked at each other apprehensively. I walked into our kitchen, parted the blinds and peered outside. No one was there. The answer to our question was there, however, in the form of a 5.25" bird, the black-capped chickadee. Flapping its wings, seemingly suspended in mid-air, it was pecking away at our door frame. Astonishingly it had pecked about an inch deep into the wood and some five inches in length. There was other damage as well, but it was impossible to determine what had caused it. In short, the doorframe had to be replaced. Termites we wondered. The exterminator said no, but other people in our condo had suffered similar damage we were told. I plugged the hole with steel wool to deter the birds. The culprit(s) did return only to be repelled by the unpleasant texture of the steel wool. The question, however, remained. What were they after?

Mystery #2. Why at 3:45 am.? Last fall the aluminum siding on our house was replaced. Since then we have not noticed the same number of house sparrows that had previously taken up residence in the eaves of our house. We had seen a few and heard a few in the trees but nothing like previous years. We have seen no bird fly into the seemingly impossible-to-get-into slit(s) near the roof which they commonly used to do. For a few weeks now both my wife and I have heard a bird singing pleasantly and somewhat loudly at a quarter to four. While we have no proof, we both believe it to be a house sparrow. We don't care that much if the singing is that of another bird. We do wonder why the bird sings at this hour. I have considered the possibility that this is a bird which was hatched and fledged in our house and perhaps not old enough yet to strike out on its own. Thus it perches in the tree pining and sighing for the lost nest of its youth. Our question and you may have guessed it by now, is, why at 3:45 a.m.?

Mystery #3. Where's the nest? The fence of our patio, metal street signs, railings, a car hood and tree branches are all perches along the feeding route of a couple of mockingbirds. It is there that they perch to look for caterpillars, insects and other tasty morsels in the street and on the grass. They then fly off basically in the same direction, which is where I assume their nest is located. I also assume that there are either hungry chicks or a mate incubating eggs at their nest, which is likely to be in smallish trees or shrubs.

It is in the misty morning that the mockingbird's dun color stands out against the still green leaves as one perches on a Stop sign. The long arched tail twitches as it turns and flies toward me. The whites of its wings and tail whirl like a helicopter, as it crosses the road and lands on another metal street sign. Bent and firmly grasped in its bill is a bug. Intensely determined, the bird looks around, stays a while and flies possibly back to the nest. In my experience, birds returning to a nest where there are fledglings to feed don't go straight there but perch nearby to check things out before returning.

One afternoon I watch a mockingbird on the Stop sign. It comes off and starts to fly to what I assume will be its next perch, the sign in front of my house. Its whites stop blazing, its wings are cupped and it lands on the wet asphalt zigzagging like a plane in trouble trying to land on the deck of an aircraft carrier. What is it doing? The bird quickly helicopters up to the sign holding firmly in its bill what appears to be a shiny green caterpillar. It looks around for a while appearing impressively grim and soon flies off. Oh, about their nest, I never seriously investigated where it was because I became fascinated with their hunting.

Mystery #4. Have they come to deposit an egg? One day I see two brown-headed cowbirds on our patio fence, a male and a female. They quickly cross the road to another lawn. There, a second female joins them. The male, its rich brown head atop a glistening coal black body, hunts alone on the grass that yields its bounty like a smorgasbord table. It gets four or five morsels, including something long and yellow. Meanwhile the two females, a drab brown, hunt together at the fringe of the lawn while constantly looking up.

The cowbird has a very interesting characteristic. It doesn't incubate its own eggs, but rather puts them in the nests of other birds hoping that they will do what it won't. I only see these birds here in the spring when other birds may be incubating their eggs. Were the cowbirds looking up at a tree for insects or a possible nest? Were they looking for predators like the mockingbirds who might chase them from the rich hunting ground? It is unlikely that the cowbird would try and place an egg in the larger mockingbird's nest, which is also an aggressive defender of its territory. If they were checking out potential nest sites to place an egg, it would likely be that of a smaller bird, possibly the house sparrow.

Standing there I silently murmur to them, "while you're at it, check out the next sites of the black-capped chickadees. If they're busy incubating an extra egg, they'll have less time to come to my door."