Videos are great and all but I found it much quicker to use a map
here is a great interactive map you can filter and compare with your in game one to find any you need http://witcher3map.com
It's currently missing one in velen. If you go south on the map from Novigrad there is a wide area of water cutting the map in 2 with 3 /4 small islands linked to both sides by bridges, the missing nest is on the right most island and it has a signpost called Hindhold on it. Hope that helps those missing the last Velen one.
Word of warning if doing these in Velen , there are 2 in the east very close together , side by side in fact that are guarded by some lvl 21 enemies.