It is also worth noting that the inboard wing is more involved in weight
support of the animal,
while the outboard wing is more involved in the production of the thrust
component of lift (note
that in flying animals thrust is just a forward component of the lift, which is
itself just the
component of fluid force perpendicular to flow).
Without a complete wing inboard, there is a significant loss of weight support,
as a result.
There is also a substantial increase in induced drag, as the inboard wing then
represents a
second, broad, "wingtip" around which a downwash can form. This further
changes the flow on