A bird irruption

Outdoors: Purple finch following red-breasted nuthatch into Eastern Iowa

A male purple finch at the F.W. Kent Park bird blind in February. Notice the more pointed bill with straight culmen. Als
A male purple finch at the F.W. Kent Park bird blind in February. Notice the more pointed bill with straight culmen. Also note the auricular area, which although dark is largely reddish overall. Also note the flanks (sides), which lack definite streaks. (Brandon Caswell/correspondent)

The latter part of August 2020 brought an impressive irruption of red-breasted nuthatch to Iowa, with many sightings continuing into early September.

It appears other species might be irrupting into Iowa over the remainder of the fall and into winter.

On the heels of the current nuthatch irruption, recent sightings in Iowa and the Upper Midwest indicate purple finch is now moving into Eastern Iowa. It is possible other finch species may irrupt over the 2020-2021 winter, such as pine siskin, crossbills and common redpoll.

Finch feeders well-stocked with nyjer seed will attract siskins. Crossbills, redpolls and purple finch like oil-type sunflower seed. Redpolls also will eat thistle seed and suet.

Purple finch breed in the boreal forests across Canada. They also breed along the west coast, throughout much of the northeastern states and through northern parts of the Michigan, Wisconsin and Minnesota. They also spend the winter months along the west coast and northeastern states, but will migrate as Far West as central Nebraska and along the Eastern Seaboard with some making it as far south as Louisiana.

Although not as common as some other winter feeder birds, the entire state of Iowa can expect them in the colder months.

Purple finch can sometimes be tough to tell recognize from the more common and sedentary house finch. However, some key field marks help to quickly separate them. When dealing with the colorful males, one of the first things to look at is the sides (or flanks). The male house finch has streaks (or dark lines) down the sides, which are absent in male purple finch. The male purple finch has more of an almost pinkish to reddish coloration, which is more extensive throughout its head and back. The auricular area (the area below and behind the eye) is reddish in male purple finch and more grayish in male house finch. Similarly, the back of the male house finch is grayish.


Female purple finch also cab be tricky to distinguish from female house finch. Both have streaking down the breast and flanks. In female house finch, these streaks are more continuous, whereas in female purple finch they can seem somewhat disconnected or shorter. The supercilium (the area above the eye, the “eyebrow” area) is a bold white stripe on female purple finch, whereas female house finch have a rather plain, uniformly colored head. Female purple finch also display a white moustachial stipe (mustache stripe) that runs from the base of the bill and along the side of the throat.

Another helpful field mark in either sex pertains to the bill. The culmen is the lengthwise “ridge” along the top of the bill from base to tip. In purple finch, this ridge is rather straight, whereas in house finch it is curved. This curvature in the house finch culmen makes the bill seem shorter.

While we don’t hear purple finch sing in Iowa — because they do not breed here — the characteristic sound to listen for in the fall and winter is a short and repetitive “tek.”


— Sparrow diversity ramps up in October. There are about 18 species that can be seen throughout the month. American tree sparrow and dark-eyed junco will slowly increase in abundance as they migrate south for the winter. White-throated sparrow will be abundant during their migration. October also is the peak for Lincoln’s sparrow. The two most sought after sparrows are the “marsh sparrows,” LeConte’s and Nelson’s. Look for LeConte’s sparrow in dense wet grasslands or sedge marshes. In Iowa, Nelson’s sparrow prefers even wetter, grassy freshwater marshes.

— Baltimore oriole will wane out pretty quickly in early October, but may persist into the first couple weeks of the month. Keeping jelly feeders out until mid-October is probably a good idea. Many homeowners who keep track of oriole migration over the years will have a good idea when to take down their feeders.

— Blackbirds are well-represented throughout the month. Scan large flocks of red-winged blackbirds for the less common Brewer’s blackbird and even a rare yellow-headed blackbird. great-tailed grackle, also less common, may be in large blackbird flocks.

— The most common warblers in October are orange-crowned, Nashville, yellow-rumped and even Tennessee.

— Hermit thrush has a fall peak in October, which counters the spring peak in April.

— Gray catbird will slowly wane out over the month as will house wren.

— Both kinglets, ruby-crowned and golden-crowned, will have numbers peaking in October.

— Barn swallow and tree swallow numbers will wane out in October.

— Hawk migration continues throughout all of October. There are about 10 species that can reliably be spotted during fall migration in Eastern Iowa. Two of the more rare sightings are golden eagle and Swainson’s hawk.

— Common loon numbers will ramp up into late October, peaking in early November.


— Around 20 species of shorebirds still are possible throughout October, especially during warmer periods and if habitat persists.

— Ruby-throated hummingbird activity will wane out at feeders as the month progresses. Similar to orioles, homeowners may have a good idea when to take their hummingbird feeders down. The latest record dates for ruby-throated in Iowa are late November into mid-December, so leaving feeders up later than usual, weather permitting, is never a bad idea.

— All of Iowa’s expected grebe species are possible in Eastern Iowa in October, with eared being uncommon, red-necked being rare and western being even more rare.

— About 23 duck species are possible to see throughout October.

Brandon Caswell has undergraduate degrees in biology, anthropology and geology. He enjoys bird-watching and nature photography. He helps instruct introductory and advanced courses in environmental science and geoscience at the University of Iowa. Email brandon.caswell83@gmail.com.

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