For four years, a mallard has nested behind a bush near the front door of Caitlin Deal’s home in a Minneapolis-St. Paul suburb, offering an up-close glimpse of nature for her young son and lessons for how people can coexist with wildlife. The duck, dubbed Martha by the family, sits on her nest for about a month every spring in the tree-lined neighborhood of Eagan, Minnesota. After her eggs hatch around Mother’s Day, the birds toddle away. “It feels nice that she trusts that area, that she trusts us to be able to come back year after year,” said Deal, whose 4-year-old son Owen’s first word was “Duck.” Spring is when wildlife — everything from birds to deer to alligators — bear their young, often in locations more suitable to humans than animals. Experts maintain that with a few exceptions and some preparation, coexisting with creatures usually is easy — and often a lot of fun.…