David in Normandy wrote:
Ditto that. Perhaps one in every fifty onions gets relocated by the
birds - and there is no shortage of birds here! Apparently the oldsters
trick is to trim off the top dead bits of onion sets prior to planting
them so the birds aren't tempted to pull them. That is probably less
hassle than setting them in plug trays. Personally I just plant them so
the tip is barely out of the ground. By the time they've rooted and
start to grow the tops of the bulbs soon appear above the surface of the
ground anyway - which I gather is important to help them ripen.

Actually, maybe my success is due to the fact that I rarely remember to
plant my onion sets until they have a huge chunk of green sticking out of
the top. :-)