Time management by ringneck parrots

Nature has lots of mysteries hidden with in it.
Ringneck parrots time management skills are amazing.
If we keep scoring, on time management between me and my parrots, I will definitely loose.
I wonder how they mange time, with out having a clock with them : )
My spike does its daily routines, as per proper time schedule with out fail.
Morning it wake up at 6.30 am. And start it morning walking & flying exercise for exactly 2 hours. It will walk two and fro with in its room and also in the open terrace.
After its morning exercise session it will have some food and it will sleep till lunch time. At 1 pm it has lunch. it will play for couple of hours and around 4 to 5.30 it will start its evening walking and flying exercise session. At sharp six o clock, It will climb on the top of the grill and sit. What ever happens, it will not come down after 6 o clock in the evening. Whether day light is gone early or the day light is still brighter at 6 o clock. It does not cares, it will be on its regular schedule with out fail.
Some ring neck parrots around home can be also spotted at exact timings : )
Morning at 6 am till 7 am and at evening at 3.30 pm to 5 pm .. We cannot track them around other than these timings.
I always wonder how parrots are keeping there time management accurately.