Keith - you ca'nt say with any certainty, yes both CC and BC overwinter but are we talking about a few hundred birds as was the case in the 70's or a few thousand birds with the mild Winters that we have had over the last 30 years? Either way compared to the European populations of these birds (some 25-50 million pairs each) we must have several hundred thousand pairs in the UK so far and away the 99.9 recurring still migrate?
Early-flowering
Goat Sallow is an excellent source of both nectar and the insects feeding on them. I watched 2 Chiffchaffs feeding on one ystda and any Chiffchaff whether overwintering or newly arrived would exploit this food source so i would'nt automatically associated a
'Nectar-head' as a newly-arrived bird but that just my opinion.
Personally i associate the arrival of migrants with the first singing birds as you have to start somewhere
Laurie:t: