What makes this ultralight's wing a training wing?

The trike flying with these colts still uses a training wing. How is this wing different from those used during migration? A training wing is all white. It has wires, or cables, that attach it to the kingpost of the plane. It is bigger (19 meters of surface area), which makes it slower and more suited to the new fliers. Click to see the wing used later on migration, after the birds can fly faster and farther. How is it different? What is the benefit of the faster wing having no wires or cables?

Training wings are bigger and slower than wings used later on migration.

Photos: Heather Ray, Operation Migration

The wings pilots use duriing the migration are faster than the training wings.