When attempting a mid-air shot with a firearm/bow, be sure to put the wyvern on follow. Otherwise it will attempt to find a place to land. Also works great to regenerate stamina mid-air like a quetzal.
To know how much time need to the next feeding just do the next. Look the Food number# then that number multiply x 10, then divide /3600 and the result will be the number of hours until the next time need to be fed. F.E the food number is 1850.5 1859.5x10=18595 /3600 = 5.1 hours