The heavy blotching instead of spotting or streaking on the breast and very dark back immediately struck me as unusual and alarm bells started ringing since those are the two main characteristics of the Icelandic subspecies coburni. That this subspecies can be distinguished in the field has only become apparent in the past couple of years and there is very little information available on how to tell them from the nominate race. As a result, it is still a very rare bird in Belgium with only three accepted records. This race overwinters in the UK, however, where there was heavy snow for five consecutive days prior to my observation so it makes sense that an Icelandic Redwing unable to forage there would continue its south-easterly trajectory and end up in Brussels. Nobody here seems willing to stick their neck out and confirm my identification as the 4th Icelandic Redwing for Belgium but I'm happy that's what it was. As a comparison, here is my picture of a bird of the nominate race. Although the above individual is sitting in the shade, the darker shade of brown (almost dark chocolate as opposed to milk chocolate) is evident, as are the heavy markings on the breast and especially flanks, where very little white is showing compared to the other bird.
