(Flocks of birds flying in this peculiar formation is a common sight In autumn and spring in the UK as birds fly from, or return to their nesting grounds.
The scientists fitted data loggers to a flock of rare birds that were being trained to migrate by following a microlight. Analysis of the data revealed that the birds flew in the optimal position - gaining lift from the bird in front by remaining close to its wingtip, thus saving energy.
Basically, they are tailgating each other.)