Polk County Conservation

Jester Park is home to two purple martin colonies. Purple martins are the largest North American species of swallow. They roost in colonies that can consist of thousands of birds. Colony monitoring used to be a much more common practice, and the species adapted to using manmade structures. Today, purple martins east of the Rocky Mountains tend to utilize artificial homes while those west of the mountain range favor their natural habitat. Colony monitors are tasked with collecting data on the colony's nesting and reproduction success throughout the summer. They are asked to change the nesting material if the interior of the nesting structure has become wet/saturated due to weather and/or when the nestlings are about 10 days old. Depending on the year, purple martin nesting areas may become infiltrated by various bugs/pests/mites. Based on guidance from the Iowa Department of Natural Resources and the Purple Martin Conservation Association, monitors may perform a nest change for pest control. However, save for the nest change when nestlings are 10 days old, monitors are not asked to perform nest changes for bug/pest/mite control. This is in part due to a 3-year study on the benefit of nest changing that revealed no clear, long-term benefit from the practice when they compared nest structures with and without nest changes.