by Kathy Freeze, Guest Blogger
The Purple Martin (Progne subis) is North America’s largest swallow. They are colonial-style nesters, meaning that they like to congregate and nest in close proximity at a particular location. After observing my aunt’s purple martin colony for years we finally moved to Missouri in 2006, and I decided to become a ‘landlord’ and start hosting purple martins. After 8 years, I now host 74 pairs and their delightful chatter, graceful flight and entertaining antics are the main attraction in my backyard for most of the summer.
Per the PMCA: Purple martins have been migrating to North America from Brazil for thousands of years. In the early years, before the first human beings arrived, the martins nested only in the abandoned nesting chambers of woodpeckers, or in the other natural cavities of dead trees or in cliffs. Today, east of the Rockies, martins nest only in human-supplied housing; either in elaborate bird house condominiums known as “martin houses” or in natural or artificial gourds. Known as a “behavioral tradition shift”, this has been attributed to several factors including the offering of gourds with holes by the Native American Indians, which were an easily obtained nesting site by the martins and later, the introduction of non-native European Starlings and English House Sparrows who took over the natural cavities. The purple martin is now the only bird species in North America that is totally dependent on humans for supplying them with nesting sites. In fact, if humans were to stop supplying martins with homes, they would likely disappear as a breeding bird in eastern North America.
Today, I offer 84 cavities consisting of a combination of aluminum housing and man-made plastic gourds located approximately 75 feet from my own home. You would think that these wild, beautiful birds would prefer to be further away from their nosey landlord; however, if their housing was located over 200 feet away by my pond, they would likely not nest there. The PMCA suggests the reason for this phenomenon is the martins feel safer when nesting closer to humans as there are likely fewer predators where there is human activity.
If I allowed the predators to freely predate my colony, the purple martins would eventually abandon my site. As they only nest and breed once a year (sometimes twice in the more southern states), they are more attracted to sites that are well-managed and predator and nest-site competitor free, or as close to it as possible.
Throughout the course of their nesting cycle, I also participate in a research program with the PMCA known as “Project MartinWatch". It’s a continent-wide, scientific project where participants monitor their martins’ nests weekly, record the information (number of eggs laid, number of eggs hatched, number of young fledged, etc.), which will allow the research group to determine the range-wide reproductive success and annual population trends of the purple martins. For some years, I have also participated in banding more than one thousand young hatchling and adult martins here at my site, which will allow us to track their returns and recoveries (deaths) in upcoming years.