Chimney Swifts are small, slender birds that have become a symbol of summer for many. They usually appear during the warm summer months before making their way to more tropical sites for the winter. They are recognized by their spectacular, chirping flocks moving through the sky in synchrony; Chimney Swifts can be seen most vividly at colonies of hundreds or even thousands of individuals, forming tornado-like funnels as they descend into a chimney. Unfortunately, the size of the colonies we see is misleading. Though the numbers may seem remarkable, Chimney Swift populations have been declining sharply since the 1970s, due primarily to habitat loss. Unlike most birds, Chimney Swifts cannot perch or stand upright, so they require long, hollow spaces that provide safe roosting and nesting sites. Historically, Chimney Swifts preferred hollow trees; however, as humans expanded their territory and replaced forests with towns, the species was forced to adapt by using other structures, such as chimneys. In the US, the large-scale shift to alternate heat sources, chimney capping, and the use of prefabricated chimneys has drastically reduced their ability to nest during migration. Newer, prefabricated chimneys are often lined with metal flues that make it impossible for the birds to grip the surface. In addition, logging and deforestation have made finding suitable overwintering habitat more challenging than ever. In an effort to sustain the remaining population, conservation groups have designed supplemental housing structures called "Chimney Towers." These towers are specially designed to provide roosting sites for Chimney Swifts, which now rely almost entirely on man-made structures like these to survive. However, because this species is remarkably adaptive, minimal conservation efforts like keeping traditional masonry chimneys uncapped during the summer months can improve their chances of survival. Which of the following best summarizes the passage?