“Yes, there is,” said Robert Mulvihill, an ornithologist at the National Aviary in Pittsburgh. “I know my position is at odds with some of my colleagues, but I don’t blame the house sparrow,” he said. “Introduced or not, they are now a fully naturalized wild North American species, and I don’t think any wild bird should be labeled the bad guy just for doing what it naturally does to survive.”

Mulvihill said he was surprised that a century and a half of nest competition hadn’t resulted in more defensive behavior in bluebirds. They just need to adapt, he suggested. Still, he told me, we can help bluebirds by putting bluebird boxes only where they belong: not near houses, barns or bird feeders, but in open meadows, which house sparrows would never call home.

“Eastern phoebes have to regroup and find safer nesting sites,” Mulvihill said, “preferably forested settings near streams, where they breed naturally.”

Eastern phoebes are an early nesting species and may have traditionally had their first brood before competition from later-nesting house sparrows, he explained. “But warmer spring weather induces house sparrows to nest earlier in some areas, and eastern phoebes may have lost their usual seasonal head start,” he said.

To Mulvihill, killing house sparrows is an all-too-typical human response. “Let’s be honest,” he said. “If bluebirds and eastern phoebes have an enemy, it is we humans, not the house sparrows we brought here.”

First, Mulvihill pointed out, we wanted the sparrows to control pest insects. “They did that, and made themselves at home.” he said. “Now, we don’t want them because they are too good at competing with other birds we want around. This is a lesson why you never want to introduce an adaptable species into a new environment because it will inevitably upset the ecological balance and create problems.”