Will this be a historic winter for bird-watching?

The trend of irrupting winter birds keeps rolling along this year.

History is in the making for this next featured species.

A 'mega flight” of evening grosbeaks occurred in the winter of 1977-78. This irruption brought them much farther south than the southernmost limits of their typical boreal forest wintering grounds. The last time large flocks of evening grosbeaks roamed around Iowa was during this remarkable event.

In the last half century, evening grosbeak was considered rare although regular in Iowa. After about 1990, sightings started to dwindle. It is postulated that a die off of spruce budworm negatively influenced grosbeak reproduction, causing a gradual population collapse and retraction of their range northward. In the last decade there have been a few sightings in Iowa and the species is now considered quite rare.

Budworm is doing well again and it is possible evening grosbeak numbers are on the rise. In late October, a pretty sudden and massive southerly push of grosbeaks was underway. On Oct. 29 the first Iowa report came from Jewell. Over the next couple days, there was a string of reports, including seven visiting the feeders east of Wapello at the Port Louisa National Wildlife Refuge.

Iowa sightings seem to have petered out as of mid-November while sightings in the eastern United States still continue. There have even been sightings as far south as Florida. It will be interesting to see how this unprecedented irruption pans out over the winter months. That last mass movement in the 1970s started in December, so only time will.

Evening grosbeaks are quite a dapper finch. They are larger than other typical feeder-associated finches. The adult male is mostly yellow with a dark neck and head. A yellow supercilium (eyebrow) adorns the top of the head and the bill is very large and ivory-colored. The folded wings show white secondary feathers sitting on dark primaries. Females and juvenile males look similar. Females are largely gray with a greenish nape (hind neck) and dark around the eyes. The flight feather pattern is similar to adult males.

Usually gregarious, evening grosbeaks can show up in a large flock and immediately begin depleting feeders. Their favorite food, by far, is black oil sunflower. It is not unheard of for evening grosbeaks to winter at well-stocked feeders. Due to their larger size and flocking habits, platform feeders are likely the easiest type for them to access.

There are many signs that other irruptive species are making their way south for the winter. These include other types of birds besides finches. For finches, both red and white-winged crossbills, pine grosbeak and redpolls are moving south. For non-finches, red-breasted and white-breasted nuthatches, black-capped chickadees, Bohemian waxwing, rough-legged hawk, gyrfalcon and snowy owl show signs of southerly movement.

In addition to the evening grosbeak irruption, this winter could shape up to be historic for other species as well.

OTHER DECEMBER BIRDS

- Migrating rough-legged hawks have shown well at the Hawk Ridge hawk watch in Minnesota this fall. They already are showing up in Eastern Iowa in numbers. Hawkeye WMA, especially out in the western portions (Swan Lake Road, Cemetery Road, Grabin Road), is a great place to look for them. They often can be found hovering in place while looking for prey.

- Look for trumpeter and tundra swans at Amana Lily Lake. This waterfowl spectacle should continue until the lake finally freezes over.

- Field birds may be abundant this winter if they follow suit with the finches. Look for large, mixed flocks of Lapland longspur, snow bunting and horned lark. Fields west and south of The Eastern Iowa Airport can be productive, especially after heavy snows, which force the birds to concentrate on the roadsides.

- Keep feeders full in the winter. Have a finch feeder dedicated to nyjer seed, a feeder dedicated to black oil sunflower and feeders with whatever other types of food desired. The dedicated feeders will ensure if finches or other rare irrupting species show up, they have a reason to stay. Sometimes evening grosbeak will spend the entire winter at well-stocked feeders, so keep the black oil sunflower plentiful.

- If you don't have bird feeders there are several places around Cedar Rapids and Iowa City that have well-stocked bird blinds. These places include Wickiup Hill Learning Center, Indian Creek Nature Center, Macbride Nature Recreation Area and F.W. Kent Park. Before visiting, it is probably a good idea to call the location to ask if their feeders are stocked and accessible. Due to both COVID-19 and the August derecho, many places, including Macbride Nature Recreation Area, are closed for the winter. F.W. Kent Park is open, however, due to the pandemic the actual blind structure is closed. The feeders, though, can be easily viewed with binoculars from the adjacent parking lot.

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