The Eurasian Tree Sparrow
outskirts of the city."
Today, after 130 years, Eurasian tree sparrows still cannot compete successfully with their larger cousins. Their relationship is like the gentle country cousins versus the aggressive street urchins. In this case, we know the latter as house sparrows, alias chippies.
Our much cherished St. Louis bird has never extended its range beyond about 150 miles from the city. The farthest from St. Louis the Eurasian tree sparrow has been found is along the Iowa border.
It's also curious that its range has extended northward, skirting the Mississippi River both in Illinois and in Missouri. It has not extended southward or westward.
Some speculate that the species has been forced northward by competition from house sparrows, but more likely differences in the natural habitats skirting the Mississippi south of St. Louis from those upstream from its confluence with the Missouri River explain why the bird's range seemed to be squeezed toward the north.
Eurasian tree sparrows--not to be confused with American tree sparrows that nest in the far north and visit Missouri only in winter--are readily identified by black dots showing on white checks. They also have a brownish crown and a small black throat patch. Unlike house sparrows, the sexes have identical plumage.
Both of the Old World finches are non-migratory, and both have similar nesting habits. They build rather bulky nests in crotches of trees, in tree cavities, under eaves of buildings and in bird boxes.
Ted R. Anderson, a research ornithologist at McKendree College in Lebanon, Illinois, once compared their uses of bird boxes in rural St. Charles County, where Eurasian tree sparrows were having difficulty competing against their city cousins. He made bird boxes with holes 1-1/4 inches in diameter, big enough for house sparrows, and others with holes 1-1/8 inches in diameter, barely big enough for the slightly smaller Eurasian tree sparrows.
He also noted that, while both species averaged 2.5 broods per year, Eurasian tree sparrows hatched three eggs to every two produced by their rivals. Anderson found that by regulating the size of bird boxes over several years, he increased the ratio of Eurasian tree sparrows to house sparrows at the St. Charles County study location.
During the non-nesting winter season, both of the Old World finch species frequently gather in roosts numbering upwards of 100. The Eurasian tree sparrows typically confine themselves to rural areas, while the house sparrows