Purple martins return to Georgia in spring

Posted: Sunday, March 29, 2009

In the birding world, few species generate more excitement than does the purple martin, a swallow that arrives in Georgia throughout the spring, with reports of "scouts" logged almost daily online.

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Purple martins, the largest of the swallows in North America, are dependent on man-made housing -- often a multi-compartment bird house or a rack of nesting gourds -- and faithfully return to the same locations each year from wintering grounds in South America.

It's understandable that human "landlords" anxiously await their return. Reports of "scouts" are watched by hobbyists nationally on an online data base (www.purplemartin.org) maintained by the Purple Martin Conservation Association (PMCA), a nonprofit conservation organization.

Purple martins commonly start arriving in southern Georgia January through March in the northern half of the state. Migration is drawn out with arrivals continuing into April.

Hobbyists marvel at the returns each year and sometimes wonder how a martin can get here so quickly after the first few warm days of spring. New research in which the PMCA participated gives some clues.

Published recently in the journal Science , a female martin -- fitted with a tiny geo-locater -- returned in spring from central Brazil to Pennsylvania in just 13 days. The feats astounded researchers. With a warm tail wind, a martin can cover more than 300 miles a day.

The first wave consists of the older martins -- at least 3 years old -- followed in a few weeks by 2-year-olds.

Martins 2 years or older are called adults, with adult males sporting full dark-purple color. Females are a bit drab with a gray breast.

One-year-old martins -- called "sub adults" -- arrive 10 to 12 weeks later than the older birds. These younger birds -- males lack full purple dress -- are more easily attracted to new housing locations.

The term "scout" is a misnomer. These are simply experienced birds that are eager to reclaim their housing. Some arrive dangerously early and may perish when cold temperatures clear the air of flying insects. Fortunately for the martins, many landlords today offer supplemental feeding of thawed crickets, live mealworms or even small bits of scrambled eggs flung into the air from a plastic spoon.

Many rural Georgian residents host martins, which are among birds that actually prefer to live near humans, perhaps because there are fewer predators.

The PMCA recently analyzed long-term data from the North American Breeding Bird Survey and found that populations overall are holding steady in North America.

There are exceptions. Michigan has lost more than 90 percent of its purple martins.

A generation ago, many people erected purple martin houses in the belief that these birds consumed mosquitoes, but according to the PMCA martins do not specialize. A martin's diet is diverse and includes many kinds and sizes of insects, from leafhoppers, flies and beetles to dragonflies, bees, wasps and grasshoppers.

In areas of decline, a waning tradition of offering housing is one cause. Even in areas of martin abundance, many people may try for years to attract them without success, or their colonies disappear.

Hobbyists may be unaware that problems such as competition from invasive non-native birds -- European starlings and house sparrows -- or predation from raccoons or rat snakes caused abandonment.

While generations of Americans have played host to purple martins -- the custom adopted from American Indians who hung out gourds -- specific techniques to help a colony thrive emerged in the past decade, based on research conducted by the PMCA and landlords.

Innovations include deeper compartments to protect nestlings from rain and aerial predators, such as owls; specially-shaped entrance holes designed to admit martins while excluding starlings; and special pole guards to thwart rat snakes and raccoons, which are common in Arkansas.



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