After a long hiatus, I came across some Waxwings today. Six individuals were perched high up on a Lime tree, taking the sun in. They were quite active, changing branches, pecking the shiny, red tree buds. Two in particular called my attention, as they approached each other touching bills, then coming apart. I took plenty of photos, some unfocused by branches getting in the way, but, looking at them in more detail back at home, I noticed that the two individuals 'billing' were doing more than that, they were exchanging an object, probably one of the tree buds, in a ritual display called 'gift passing' (top shot). The behaviour is seen both in the Bohemian Waxwing, which we get in irruption years in the UK, and in the American Cedar Waxwing.
I found a description of the behaviour, based on captive individuals and illustrated with photos, which shows that the display is also accompanied from fluffed rump and belly feathers, raised crest and lowered tail, the latest something not very obvious in my photos. The male appears to initiate the behaviour, obtaining the object, and sidling to the female, presenting it. If successful she will accept the object and reciprocate, after jumping away, then close. It is difficult to sex Waxwings, males apparently have longer crests and a more clearly delimited black chin patch.
This is a clip of the behaviour in the Cedar Waxwing, there seems to be a lack of recordings for the Bohemian Waxwing, although the description and my observations fits both species sharing this wonderful display.