In Corso et al. (2014), the pattern and coloration of the underside of the outer primaries was described as one of the most important features in differentiating Slender-billed Curlews Numenius tenuirostris from Eurasian Curlews Numenius arquata. However, the authors noted that this feature was not always clear-cut, with some Eurasian Curlews showing a pattern on the outer primaries that approached that of Slender-billed Curlew and, similarly, some Slender-billed Curlews showing a pattern approaching that of Eurasian Curlew (see Corso et al. 2014). A juvenile female curlew collected at Veneto, northeast Italy, on 1st August 1896 (MCZR 15733; plate 185 in Corso et al. 2014), was genetically confirmed as a Eurasian Curlew (Tan et al. 2023). The pattern shown by this bird on P10 and P9 (the outermost two primaries) resembled that expected for Slender-billed Curlew and would have scored 2 for P10 and 3 for P9 as per the scoring system laid out below. This bird, and the variation shown within the two species generally, highlighted the need for refinement of assessment of the underside of the primaries.