I'm not quire sure but, I was thinking about swallows today and where many of them nest. Before human development, I'm kind of imagining lower numbers of a couple swallow species. The number of cliff swallows that nest under bridges is staggering. Are there enough cliffs around that today's numbers could have existed? And barn swallows? Under bridges and in many buildings all over. Where did they nest before human development? I can't picture there being as many barn swallows if humans weren't here. Then I wonder the impact... IF their were lower numbers of swallows, there were likely much higher numbers of many other birds as there'd be more habitat AND more food available. Random thoughts.