I moved my black currant bushes over the winter and they are now in front of our living room window. We have several active starling nests and have noticed that they fly down, quickly nick off a leaf and fly off? Is it to get the a black currant nest freshener – or is there another reason?
I believe that they are aware of the medicinal properties of blackcurrant leaves and are using them for that. They are cleansing and diuretic.
There is a whole branch of science studying how animals use plants for medicinal purposes (zoopharmcognosi), which I think is fascinating. Good evidence of starlings using thyme when they have a lot of bugs in the nest that are annoying them.