Here's a map from a previous post, showing the Wisconsin and Illinois counties highlighted in red where the bulk of reports of European Goldfinch come from.
In a previous post, I documented nesting in Waukegan, Illinois, which is in Lake County. Later, I found a report online of a family of European Goldfinches at Waukegan Beach on 13 August 2009, consisting of five birds: two adults, and two juveniles, with the fifth bird likely also a juvenile. The observer posted this photo on Flickr. The day before the photo was taken, another observer saw a minimum of 13 European Goldfinches foraging in a weedy area in what appeared to be two to four family groups in an area just adjacent to Waukegan Beach.
In 2011, European Goldfinches were reported nest-building at Waukegan Beach. A report in April 2012, just a couple weeks ago, also mentioned them gathering nest material. So it seems a breeding population is well-established in the Waukegan area.
These may not be the first European Goldfinches to have nested in Illinois, as there was also a report of birds nest building at Montrose Point in Chicago, Cook County as early as 2003.
In Wisconsin, the breeding population seems centered in the Racine area of Racine County. That is around 25 miles north of Waukegan. My previous post documented a juvenile in 2009 in the Racine suburb of Mt. Pleasant. Subsequently, I received a report in late July 2009: the Scheefs in suburban Racine reported on a juvenile showing up at their feeders shown in this post.
I also heard from Sarah Anspaugh of Racine, who took the photo below of a European Goldfinch family. A pair showed up at her feeder on 13 May 2009, appeared periodically through June, and on 8 July 8 there were 2 juveniles with them.
Jane Scheef of Racine contacted me again in 2010. The pair in her neighborhood arrived at her feeder on 29 June with 5 young in tow, shown in the photo below.
I think that an eBird report of six to eight coming to a feeder in Racine in late winter 2011 may be the same residence. The largest flock I have heard about was that of 30 on 4 December 2011, also in Racine (I think this checklist is the exact location).
Finally, in between Waukegan, IL and Racine, WI is Kenosha, WI, where a correspondent named Donna has had at least one pair of European Goldfinches at her feeders. In June 2011, she photographed them with three young. She recently wrote me that a pair is currently coming to her feeders.
Unlike American Goldfinches, European Goldfinches typically nest in May and June, so be on the lookout and keep sending those reports.
Here are my other posts: