Functions for range estimation in birds based on Pennycuick (2008)
and Pennycuick (1975), 'Flight' program which compliments Pennycuick (2008)
requires manual entry of birds which can be tedious when there are hundreds
of birds to estimate. Implemented are two ODE methods discussed in Pennycuick (1975)
and time-marching computation methods as in Pennycuick (1998) and Pennycuick (2008).
See Pennycuick (1975, ISBN:978-0-12-249405-5), Pennycuick (1998)