Nice shots.
Great job on those, but in terms of tips or things to think about:
- Whenever possible try to get down to eye level instead of shooting down on ground or water level birds. That's often not an option, but sometimes it just means kneeling down or lowering the tripod so if it's possible it's worth the effort. It gives a much nicer angle and tends to separate the bird better from its background making it pop. The first shot looks to have a lower shooting angle though it might just be farther away but the separation in the top half of the image is what you can often get by getting down low to shoot or shooting from farther back with a longer lens to flatten out the shooting angle.
- Even though the feet are obscured by the grass in the lower photo it's best to include where the feet would be rather than chop them off mid-leg.
- I'd probably give that second shot more breathing room and include a little more environment.
Those really are nice shots but since you requested tips, those are things that come to mind.