A European bird invasion

Many familiar birds of the urban environments represent species that were introduced from outside of North America.

In Iowa, these include rock pigeon, European starling and house sparrow, which was formerly called English sparrow.

The desire for European settlers to see familiar birds is largely the reason these non-native species were released. English colonists released rock pigeons in the early 17th century. Both European starling and house sparrow have ties with New York City.

Dozens of starlings were introduced into Central Park in the 1890s by Shakespeare enthusiasts. The house sparrow was likely introduced in Brooklyn in the mid-19th century for insect control. Within about 50 years, it spread throughout much of the United States.

Another introduced species, which is showing an uptick in expansion, is the likable Eurasian tree sparrow. Released in St. Louis from a small caged population more than 150 years ago, they have slowly spread up the Mississippi River toward the area where the states of Missouri, Illinois and Iowa all converge.

For well over a decade, their numbers have been growing in southeast Iowa. Cities like Davenport have large flocks along the Mississippi River. In some areas they even outnumber house sparrows.

In the last decade, Eurasian tree sparrow has been slowly but steadily increasing its range in Eastern Iowa. This steady dispersal seems to be facilitated by their ability to follow tributaries of the Mississippi — such as the Iowa, Cedar and Wapsipinicon rivers.

Eurasian tree sparrow is sexually monomorphic, which means males and females look alike. They are notable for their chestnut crown, black throat, and white cheeks with clearly visible black cheek patch.

While Eurasian tree sparrows can sometimes be found at feeders, larger flocks prefer sparsely wooded riparian zones. House sparrow may be slowing the spread of Eurasian tree sparrow into more urban areas. However, they certainly are becoming more common to see mixed in with large house sparrow flocks in more rural settings.

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Being a cavity nester, Eurasian tree sparrow can nest in tree cavities or cavities in poles, fences, buildings or even in bird nesting boxes. Males court to form pair bonds and remain largely monogamous after that point. I once observed a male courting a female along the west side of Terry Trueblood Recreation Area in Iowa City. The male had taken over an old woodpecker nest and was wooing her to join him by fluffing up his feathers and vocalizing.

What future lies in store for the Eurasian tree sparrow in Iowa? At this point, the data shows a trend of continuing expansion. Similar to problems created by house sparrows, birder observations already demonstrate Eurasian tree sparrow will be another contender for things like bluebird and tree swallow nesting boxes.

Once perceived as more rural, they are increasingly starting to show up in urban environments. While dapper and enjoyable, their expansion probably means more unnecessary competition for our native bird species.

WINTER BIRDS

If you want to see Eurasian tree sparrows, an excellent location is at the “Amazing Space” bird feeders of Indian Creek Nature Center. Old River Rd SW in Cedar Rapids, near the roller dam and along nearby riparian areas, is another place to look. In Johnson County, one of the best places is a small bridge near the intersection of Swan Lake Rd NW and Half Moon Ave NW, which is located at Hawkeye WMA.
The recently renovated bird blind at Macbride Nature Recreation Area is an excellent place to see wintering birds. These include tufted titmouse, black-capped chickadee, dark-eyed junco, red-headed woodpecker, white-breasted nuthatch and sometimes red-breasted huthatch and Carolina wren.
The western portions of Hawkeye WMA along Swan Lake Rd NW, north of its intersection with Cemetery Rd NW, is a great place to look for diurnal raptors, such as northern harrier. At dusk there is a possibility of seeing harriers and short-eared owls. Eventually, the harriers will disappear to roost for the night while the owls will continue hunting throughout the night. Sometimes skirmishes occur between harriers and owls. The Eastern Iowa Airport is another place to look for short-eared owl. Look late evenings before dusk and into dusk along Cherry Valley Rd SW and Walford Rd. If snow eventually covers all of the grassy habitat at the airport, the owls may decide to relocate.
Any roller dams along rivers are places where waterfowl can congregate, especially during very cold periods. Tailwaters areas, such as at Coralville Lake, along with any lock and dam along the Mississippi, can attract a variety of birds. These include bald eagle, American white pelican, gulls and various waterfowl.
Scouring the rural roads for wintering raptors, such as red-tailed hawk and rough-legged hawk, can be a fun activity. Especially when it is really cold outside. Birding from an automobile is warmer and also provides a type of blind if doing photography.

Birding calendar

The Christmas Bird Count season is upon us. Be a part of the United State’s longest-running citizen science project. All skill levels welcome.

Dec. 17 — Cedar Rapids Christmas Bird County. Visit iowabirds.org and click on “Upcoming Events” for more details.
Dec. 18 — Iowa City Christmas Bird Count. Visit iowacitybirdclub.org for more details.
Dec. 28 — North Linn Christmas Bird Count. Visit iowabirds.org and click on “Upcoming Events” for more details.

Brandon Caswell has a keen interest in natural and social sciences. He enjoys bird-watching and nature photography in his spare time. He and his wife live in Marion with their two children.

A Eurasian tree sparrow forages with other sparrow species at Cedar River Crossing in Johnson County in mid-October. It was part of a post-breeding flock of around 50 individuals. (Brandon Caswell/correspondent)

One of four Eurasian tree sparrows (bird on left) visiting feeders along Fox Trail Drive NE in Cedar Rapids. Drastic changes in habitat along Dry Creek, due to the 2020 derecho, possibly facilitated their recent dispersal into this neighborhood. (Brandon Caswell/correspondent)

A bald eagle roosting in a tree along Cedar Lake, just south of the Sag Wagon, in November 2022. (Brandon Caswell/correspondent)

An American goldfinch visits feeders at Macbride Nature Recreation Area in November 2022. The recently renovated bird blind area is located near the Iowa Raptor Project’s live displays. (Brandon Caswell/correspondent)

A tufted titmouse visits feeders at the recently renovated bird blind at Macbride Nature Recreation Area in November 2022. Tufted titmouse can be seen all year at this location. (Brandon Caswell/correspondent)