An illustration of a male Blue-headed Wagtail by Henrik Grönvold
Illustration by <a href="https://en.wikipedia.org/wiki/Henrik_Gr%C3%B6nvold" class="extiw" title="en:Henrik Grönvold">Henrik Grönvold</a> (d. 1940); in a book by <a href="https://en.wikipedia.org/wiki/Arthur_Gardiner_Butler" class="extiw" title="en:Arthur Gardiner Butler">Arthur Gardiner Butler</a> (d. 1925)
between 1907 and 1908 <div style="display: none;">date QS:P,+1907-00-00T00:00:00Z/8,P1319,+1907-00-00T00:00:00Z/9,P1326,+1908-00-00T00:00:00Z/9</div>
<a rel="nofollow" class="external text" href="https://www.biodiversitylibrary.org/page/8993958">Birds of Great Britain and Ireland, Order Passeres, vol. I, plate 50</a>