Q:

Which Camera is better to take photo of wild birds? 

I am evaluating to buy one of the following cameras, that my friends have suggested to me:

a second hand Nikon D5000 camera selling @ 1000 (plus a 55mm - 200mm Len)
a first hand Nikon coolpix L310 selling @ 319
a first hand Nikon coolpix L810 selling @ 399
a first hand Canon 600D selling @ 1049 (kit lens)

From the website, I have noticed that the Nikon Coolpix L810 has a 26x factor (angle of view equivalent to that of 22.5-585 mm lens in 35mm [135] format) but I was wondering if it will be better than the Nikon D5000 200mm Lens? 
My aim is to take photo of wild birds.  Do let me know if there are questions.  
Also, my friends say that the DSLR camera is much more harder to maintain but I don't want a camera that can take no quality photo: can you help me to assess this statement? 

A:

From a camera perspective the Nikon D5000 and Canon 600D are both perfectly usable and powerful enough for wildlife photography.  However, neither one has a kit lens that would be useful for wildlife, especially birds. 
As a very general rule of thumb, 300mm is the minimum for larger game, 400mm for larger birds, and you can never have enough focal length for the smaller birds.  Often you'll find pros with a 600mm lens with a teleconverter to get even more length.  With lenses of this length you have to start thinking of a good support structure like a good tripod with a good head. 
However, there are good budget means to get adequate length for birding such as the Sigma 150-500 and 50-500 lens and the Tamron 200-500 lens.  They are available for several camera manufacturers including Nikon and Canon.  They give good performance for the price but they have limitations, too. 
Another popular way of doing birding where you get a lot of length is with digiscoping.  In this technique you use a spotting scope, which typically has more of a telescope like power, and add a camera to the end.  Some rigs cost more than expensive lenses but with better focal length but some are more affordable. 
Lastly, consider how much work you're willing to do for bird shots.  You can get by with shorter lenses if you're willing to put in the work to use blinds and other techniques to get closer.  The best birding pictures are those where the photographer has worked their way into a great position that doesn't interfere with the birds, is in good light, and a well chosen background.  Also learning bird behavior is essential to good bird photography.  The more you learn the more you can work around equipment limitations. 

A:

At the risk of contradicting everyone, the one with the longest zoom will be better for non-professional bird photography.  On your list, that is the L810 but I would recommend a camera with more controls over that one, such as the Nikon P510 which I just reviewed and has a 42X optical zoom reaching 1000mm.  It is available for $429 USD. 
Why?  Because what makes the photos great is how close you can zoom in to see the birds up close with lots of details.  Of course, you will lose image quality and speed which are important things but when it comes to a photo, its contents always trumps technical characteristics. 
If you want to be serious about bird photography and catch birds in flight, the you will have to go the DSLR route but, while any DSLR will do, you will need big, heavy and expensive glass to get the kind of framing which makes compelling bird photos.