Here is the full list of all 20 Xbird achievements.
40 KILLS
35 KILLS
30 KILLS
25 KILLS
20 KILLS
15 KILLS
10 KILLS
5 KILLS
3 KILLS
Time in game 130 minutes
1 KILL
Time in game 120 minutes
Time in game 90 minutes
Time in game 60 minutes
Time in game 30 minutes
Time in game 20 minutes
Time in game 10 minutes
Time in game 5 minutes
Time in game 1 minute
Time in game 10 seconds