Eurasian Tree SparrowPasser montanus
Brought from Germany, about 20 of these birds were released in St. Louis in 1870. The population took hold there, and they might have spread except that the House Sparrow, seemingly more aggressive and adaptable, reached the St. Louis area at about the same time. Eurasian Tree Sparrows are still found in parts of Missouri and Illinois, and have reached southeastern Iowa, but they are fairly local in farmland and suburbs. The tougher House Sparrow may keep them out of other areas.