Update: There is an updated version of this article availabe at my photography blog:
http://markusjaisphoto.com/lenses/choosing-a-lens-for-bird-photography

Today I want to write about which telephoto lens is best for a bird photographer.
Let me tell you in advance that this is my personal opinion. Nature photographers like to discuss this topic a lot, especially if a 500mm or a 600mm lens is best.
I will just start describing the various choices and what I use:

70-200mm

That’s a popular zoom range. Nikon offers a 2.8/70-200 VR. Canon offers a 2.8/70-200 IS, a 4/70-200 without IS and a 4/70-200 with IS (which I use). VR stand for “vibration reduction” and IS for “image stabilization” and describes a technique to reduce the vibration of the lens when hand holding it or even when on a tripod. The 70-200 lens is too short for most bird pictures, but can be handy for tame birds like swans in a park or if you want to photograph a landscape with birds in it.

300mm lens

A 2.8/300mm lens is used by many photographers. Both the Nikon and Canon lenses are extremely sharp and have very fast AF (Autofocus). But 300mm is still to short for most situations. That’s why you will see most photographers who use a 2.8/300 using 1.4x or 2x extender with the lens. The 2.8/300 lenses are not cheap and cost several thousand Euros or Dollars. A cheaper choice is a 4/300 like the Canon 4/300 IS (which I use, too). Those lenses are also very sharp but much lighter and cheaper. The downside is that you will lose AF with many cameras when using a 2x extender with that lens. My Canon EOS 40D will not autofocus with the 4/300 and a 2x extender. The current Version of Nikon’s 4/300 does not yet offer VR (the Nikon 2.8/300 does have VR).

400mm lens

Canon and Nikon both offer a 2.8/400 with VR/IS. That’s a heavy beast (the Canon weighs more than 5kg ) and very expensive. I do not recommend that lens for bird photography. It’s too heavy, in my opinion and 400mm is still not very much when it comes to birds. But keep in mind that many photographers use that lens successfully, especially with good 1.4x and 2x extenders.
Canon also offers a 4/400 IS which is very light. That would make a great lens for flight photography and many photographers use it successfully. Some claim that it’s not as sharp as Canon’s 4/500 and 4/600. Canon also offers a very light and small 5.6/400 (without IS) which is very popular for birds in flight as it can be handhold for a long time.

200-400mm lens

Currently only Nikon offers a 4/200-400 lens. Canon does not although many Canon photographers (including me) would love to see such a lens. The Nikon lens is a dream of a lens. Very sharp and fast AF. Together with Nikon’s great D300 and it’s 1.5 crop factor, that lens would be like a 4/300-600 – a dream for bird and wildlife photographers. The downside of the lens is the high price.

100-400mm

Canon offers a very good 4.5-5.6/100-400 IS and Nikon a 4.5-5.6/80-400 VR. They are much cheaper than the 4/200-400 from Nikon and also much lighter. The sharpness is good, although not as good as with the 4/200-400 or 2.8/300. AF is slower due to the smaller f-stop. Nikon’s 4.5-5.6/80-400 is particularly slow, especially when used with an entry level DSLR from Nikon.

500mm

Canon and Nikon both offer a 4/500. Canon already introduced IS many years ago for this lens. Nikon recently (finally!!) came up with a new version of it’s 4/500 with VR. For me the 4/500 is the perfect bird lens. I love my Canon 4/500L IS. Those lenses are very sharp, f4 is still good, and they deliver amazing quality with a 1.4x extender and even with a 2x. I can handhold it for a while and have used it successfully for birds in flight like Black-headed Gulls, Griffon Vultures and Cinereous Vultures. It will still fit in a backpack that you can take with you on a plane. It’s cheaper than the 4/600 and although heavy (the Canon around 3.9kg). it’s still much lighter than the 4/600. That are the reasons why I chose the 4/500 over the 4/600. I use it a lot with a 1.4x extender on my Canon EOS 40D. That’s a dream combination for bird photography, as is Nikon’s 4/500VR together with the D300.

Eurasian Tree Sparrow, EOS 40D, EF 4/500L IS, 1.4x

600mm

The 4/600 lenses from Canon and Nikon (recently also with VR) give you a longer reach than the 4/500. That’s the only advantage of the 4/600 over the 4/500, but a significant one. If you are shooting a lot of shy birds and don’t have to travel by plane a lot, the 4/600 might be a better choice than the 4/500.
The best would be to own both, the 4/500 and the 4/600 but that’s quite an expensive option. I do not own the 4/600.

800mm

Recently Canon introduced a new 5.6/800 IS. It’s lighter than the 4/600 but more expensive. I would prefer the 4/600 + 1.4x as this is a more flexible solution but I am sure some bird photographers will be very happy with Canon’s new 5.6/800.

200-500mm

That lens does not yet exist. But what’s needed is a 4/200-500 with IS/VR from Canon or Nikon with a weight not over 3.5kg and the optical quality of Nikon’s 4/200-400. That would be the killer lens for bird photography. The zoom advantage would be great and allow for a much better composition of an image without the need the change your position of the lens (which is often not possible). I really hope that Canon or Nikon will come up with such a lens in the future.

You can buy some of the Canon lenses described here in the birdingnet store. There you will find the Canon equipment I use currently or used in the past (the 100-400L witch I replaced with the 4/70-200 and 4/300).