To shoot birds 1/15th of a second is way to slow, heck to shoot anything is way to slow.
General rule for stationary targets is 1/Focal length = Shutter Speed.
ie 50mm lense then minimum shutter for sharp images is 1/50th (hence 1/60th being standard for allot of indoor stuff).
for a tele you can see you are going to want say 200mm focal length 1/200th of a second say 1/250th to be safe.
Try shutter priority
mode or manual
mode.
Some settings I would suggest to capture a bird in flight,
F8 (F5.6) aperature, 1/500th or 1/1000th of second shutter, ISO200 or ISO400. Should get you a nice sharp image, providing AF locks fast enough (auto focus).