Question 1006968
With a tailwind, a bird flew at a ground speed of 3 miles per hour. Flying  the same path against the same wind, the bird travels at a ground speed of 1.5 miles per hour. 
What is the bird's air speed? 
It's the average of the 2 groundspeeds.
--------
What is the wind speed?
The difference between airspeed and groundspeed.
====================
PS  That's very slow for a bird.  30 - 40 mi/hr is common cruise speed for common birds.