It's Google being helpful, innit? "there aren't many results with blueberry and catkin in so I'll give you all the results which have either blueberry or catkin as well"
Hence a page of text hits talking about blueberries with a line of images of willow catkins.

If you search instead for "blueberry catkins" (with the double quotes so that Google searches for the phrase not the individual words) it's interesting - David is not the only one - happened to two people on allotmentsforall.co.uk and one on growfruitandveg.co.uk

Takes urglers to give an accurate id though! ;-)