Help needed, birding with a D5000.

Like sjgcit, I am impressed by your images and think you might be getting the most out of your kit.  Cropping will give you the impression of a nice bird closeup but there are drawbacks.  Cropping increases noise and distortions.  Compensating by sharpening sometimes has limited value.  Since you are cropping many of your images, the better solution might be to save your money until you can get a longer lens.  Or, increase your own stalking abilities and get closer to your subjects.  Also, when you are cropping, you do not see that, in the original frame, the bird is a lot smaller and good focus is more difficult because of that.  Given that a longer lens is probably out of your budget at this time, I would not worry about the lens and just improve your technique--which is already pretty good.  Nice work!

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www.flickr.com/photos/brev00