One Lease Agreement That Is For The Birds

Neighbors/ Severna Park

May 16, 1991|By Robert Lee | Robert Lee,Staff writer

Some families will do anything for waterfront property on the Severn.

In a purple martin community in Sullivan's Cove, nature's lease on an apartment for a young family looking for a starter home means cuckoldry for the male and suffering an average of 2.2 rapes at the hands of their landlords for a female.

"That's some condo fee," says Ornithologist Eugene Morton, a researcher for the Smithsonian Institution at Washington's National Zoo.

Morton has been unraveling the mysteries of the unique landlord-tenant relationship since he moved into his Sullivan's Cove home in 1975.

Raising martins began as a hobby for Morton, who now keeps three "high rise" units with 24 apartments each in his front yard. It's something Americans have done for centuries, going back to the Cherokees, who hollowed out gourds for them.

The largest member of the swallow family, martins are valued for their songs, their voracious appetite for bugs and their ability to chase away crows that can devastate a corn harvest. French fur traders also reported that one could collect the martins whole at the end of the year and grind them into a martin powder that repels bugs and moths.

Man-made martin houses have become the most common nesting area for the birds who naturally live in woodpecker holes.

Morton only decided to conduct a full scale study of the breeding habits of his annual guests after hearing aninexplicable bird-song and witnessing several rapes (euphemisticallycalled "extra pair copulations" or "EPCs" by ornithologists) in his garden.

Morton's research shows that worms aren't the only things early birds get.

Each year, in the first weeks of April, adult martins arrive in this area after a tremendous journey from their winterroosts in the urban parks of southern Brazil.

These mature males pick out choice penthouse apartments and battle among themselves to control as many other units as possible so they can lease them out to younger birds later.

One now-fabled male -- his purple martin's majesty perhaps -- reigned over an entire 24-unit condo for four years,Morton says.

Once control over the apartments are established, the older female martins arrive and all the adults match up into monogamous couples. The couples spend the next month building nests, copulating and laying eggs.

The martin houses resemble the picture of suburban bliss familiar along the rest of the Severn, until about mid-May when the elder males start acting very strangely. With all the young wives happily committed to marital bliss and egg-laying in their respective nests. The males -- ever seeking EPCs -- begin to wander.

Each morning at about 4:15 a.m., the adult males start flying out above the river. Each one taking his own slow circular path, and singing his own unique song.

The piercing song notes cover 30-square-miles of ground and hundreds of cubic miles of air attract yearling males who have just arrived from Brazil and are presumably looking for some affordable housing so they can start a new life.

Initially, Morton was at a loss to explain why these elder males would spend theirmornings singing a song that brings young, feisty competitors into their feeding turf.

"The question that really prompted this study was why would the males be singing these damn songs in mid-May insteadof guarding their mates like they usually do," Morton said.

Then he made the connection that the young males, in turn, attract young females, and . . . "More EPCs. That's the name of the game. That's whythey breed (in colonies); it allows the older males to produce more young than they can care for," Morton said.

Morton made the connection watching the elder males, now finished with their nest-building chores, lurk around in his garden in wait of unsuspecting and fertileyoung females.

"They have a Machiavellian intelligence," he said."They have the ability to remember past interactions and figure out future interactions.

"It all happens very quickly -- copulation just takes a couple of seconds. If an older male gets within a meter orso of a yearling female when she's gathering nest materials alone that's all it usually takes," Morton said.

"The female always looks very indignant after an EPC," he said. "But we're still trying to figure out whether they encourage EPCs as a means of trading up for superior genes."

Martins raise between 4 and 6 chicks in their nest-holes each summer.

And all the luring and lurking pays off for the elder males where it really counts. DNA "fingerprinting" studies conducted by Morton show that of the chicks raised in elder martin nests 96 percent are legitimate. By contrast, only 29 percent of the chicks raised in the yearling nests are the genetic offspring of the yearling males.

Morton speculates that the young males don't have any clue about what is happening until the next year when they make the early trip north with their elders.

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