200-500 is great lense. it also weight 83 ounces or about 4 times the weight of the lense you reference. so if that is not a problem go for the 200-500. great lense I use it all the time(although I am not a birder)

photoshop also has a 'camera raw' filter which may be useful if you are not happy with the jpeg file. I am not sure how much this filter degrades the file but it does allow adjusting a jpeg in adobe camera raw.

I love this lense but it takes some getting used to-at first your feet will be in the image-at 14 mm it picks up everything in all directions with a cone of vision more than your eye. your subject will appear far in the distance with a lot of asphalt in the foreground at first. extending the tripod to its highest point helps reducing foreground. much distortion. things seem way further away than they are. I find myself pointing it up more often. Its good for landscapes and interiors as someone mentioned. its a great piece of glass for clarity sharpness and color rendition. Its also an 'in your face' type lense. In other words the lense needs to be in the thick of the subject a few feet away at the most. some say its good for 'getting it all in' but its not the point of the lense necessarily, although I have seen some great mountain landscapes and urban tops of skyscrapers images taken with this lense.