Some time ago, I discovered what must be North America's strangest subculture. All across the eastern half of the United States, thousands of people put up specially designed nest houses or gourds to attract a gregarious songbird known as the purple martin (Progne subis subis), the largest member of the swallow family. These people call themselves “landlords” and act as care-takers for purple martin colonies during their breeding season. This quasi-symbiotic relationship between man and Progne subis goes back to the Chickasaw and Choctaw, was taken up by both White settlers and Black slaves, and continued on to the present day. It turns out that the martins probably can't survive east of the Rocky Mountains without human management, to a large extent due to competition from two non-native species, the Common Starling and the House Sparrow. The purple martins have adapted themselves to human management by learning to nest in colonies, and to seek out human habitat for nesting, something the populations west of the Rockies apparently don't do (these populations breed “naturally” and belong to two separate subspecies).
“Purple Martin Book” is a lavishly illustrated beginner's guide for people who want to become “landlords” and attract these particular birds to their back yards or front lawns. Management of purple martin colonies strikes me as a time-consuming hobby, almost like breeding pigeons or cage birds! Many landlords have nest houses that can be lowered from their poles, so that the landlord can inspect the birds' nests, remove parasites, or plug nest holes used by intruders such as House Sparrows. People also feed “their” colonies with mealworms or crushed eggshells, and defend them from predators by outfitting the nest houses with owl guards, and the poles with predator guards. (And, I suppose, by keeping the house cat indoors!) The colony can survive cold weather by the landlord placing a light bulb in the centre of the structure, making you wonder what happens to the birds during a black-out! During hot weather, some landlords gently sprinkle the nest houses or gourds with cold water from a hose. I'd say these birds are spoiled!
The book also contains extensive information on purple martin behaviour, including the complex interactions within the colony between males and females, or between breeding birds and “floaters”. Thus, “Purple Martin Book” could be of interest even to people with no particular plans to manage a colony of their own. The photos are in full colour, and show birds, various kinds of nest houses, and some of the proud landlords. Addresses to purple martin-devoted organizations, and business selling supplies related for this hobby, are also included. Of course, the landlords don't see it as a hobby, but as a serious conservation effort. Which, in a sense, it is. One issue not mentioned is whether the purple martins, which apparently are pretty sensitive to both cold and hot weather, will manage to cope with climate change. Habitat destruction in their Brazilian winter quarters could be another threat, and the local authorities in Sao Paolo have long viewed the enormous flocks of migratory purple martins as a public sanitation nuisance.
I suppose the fate of Progne subis subis depends to a great extent on how well their Homo sapiens care-takers will fare. Only time will tell whether or not it was a clever evolutionary move of these birds to make themselves dependent on The Crown of Creation…