I read with great interest the article “Nesting Instincts” in your recent Spring 2018 ON Nature magazine about the barn swallows. The new structures built to replace existing barns/bridges/etc. have been erected with ready to occupy nesting cups. As the article states, instinct would lead swallows to build where and how they have always built – ledges. Could ledges not be installed to better replicate their natural instincts? I think it would certainly be worth a try and an inexpensive fix if it works.
I greatly enjoy reading ALL the articles in your magazine. Thank you.