I hesitate to write a top 10 list as many perceive these as click bait. Hopefully, those that follow me, will know me better than that. At any rate, here are the main mistakes I see wildlife photographers making.
#1 - Photographers don't get in Close Enough
Many photographers, and particularly new photographers, have a difficult time composing portraits of animals. What I most often see from new folks, is a portrait that only takes up less than 1/4 of the image area. Now, this might be a valid approach for an experienced photographer looking to create an environmental portrait of the subject, but for beginners I recommend getting closer. This can be achieved two ways. First, if possible, get physically closer to your subject. This might involve using a blind or using a stealthy approach. Secondly, use bigger glass. If you can afford it, buy a zoom lens like the Sigma 150-600 C. Just remember that long lenses require a whole new set of worries. Start with medium telephotos such as the Tamron 70-300 SP VC or the Canon 70-200 f4L. Get in close and fill the frame! After mastering this, move on to creating more compelling compositions. The image below provides a level of detail and impact because the subject fills the frame.
#2 - Photographers Over-sharpen Their Images
Just go out to Flickr, or your favorite social media platform and browse through the wildlife images. Many have been over-processed and over-sharpened. When they become over-sharpened, the image takes on strange artifacts and edges that don't look realistic. I believe the reason most people do this is because they are trying to compensate for a blurry photograph. If you have a blurry image, then you missed the shot. Go back and try again. There is no shame in this and most of the greats do this quite frequently until they get it right.
#3 - Using Too Slow of a Shutter Speed
OK, smarty pants, how fast is fast enough? Well, like many things in this world, it depends. For the sake of brevity, use as fast a speed as your lighting conditions will allow. For example, if you are shooting birds in flight, and you want the wings to be frozen, a shutter speed of at least 1/1600 should be used (as a rule). The faster the bird can beat his wings and fly, the faster the speed. Shooting swallows requires a speed of at least 1/4000 for best results.
When shooting a static subject, perhaps a bird perched on a branch, I like to use the reciprocal rule. Using full frame cameras, you should be able to set your shutter speed at 1/500 to handhold a 500mm lens. However, when shooting an APS-C, you have to take into account the crop factor. When shooting a 500mm with my crop sensor camera, I like to be in the 1/1000th of a second range. Note that this also does not factor in using image stabilization. With image stabilization on my Sigma 150-600, I have shot handheld at 1/125th of a second at 600mm with a static subject. For beginners, I recommend keeping the shutter at 1/250th even with VC engaged.
Don't forget, rules can be broken, but right now I am giving you hard fast rules that will get you pointed in the right direction. Don't send me a long list of "but, what about..." emails. I know all about the exceptions to the rules :) Using a high shutter speed has frozen the egret below in mid-flight.
#4 - Spooking the Wildlife
Animals have what is often called a "fight or flight" zone. What this means is that each animal, through conditioning and just plain innate behavior, has a mental circle drawn around itself that predators are not allowed to enter. In the human world, we might call this "personal space." When the photographer enters this zone, the animal is going to do one of two things. He is going to run or he is going to attack you, but only if he feels threatened. Too many photographers approach the animal too quickly and too aggressively and flush the subject.
You must approach slowly, very slowly and without making noise. For birds, approach is best done from a prone position. Move forward a few feet, take a few shots, then move forward again. Repeat this process until you get the composition you would like without causing the animal discomfort. Obviously any technique depends on how conditioned an animal is to humans. In some cases, you can simply walk slowly up to your subject and begin taking photos. With any wild animal, I recommend using extreme care when on the approach. In some cases, you may actually be able to get the subject to come to you. This allows the animal to be in control and this makes for better behavior shots. The shot below was made by slowly approaching this skimmer over time.
#5 - Using a Poor Tripod
You are going to hear this from just about every advanced photographer on the net, but it bears repeating. There is simply no substitute for a good tripod (when you need one). This is especially true with wildlife photography. When you set a 8 pound rig on a flimsy tripod, you are asking for micro vibrations and maybe even tripod leg failure at some point. You paid thousands of dollars for your rig and you are going to set it on a 50 dollar tripod? Are you also a low information voter?
For economy and strength, I recommend the Manfrotto brand. You will not be disappointed with Manfrotto. If you want to step up, I would go with the Induro brand.
#6 - Buying Expensive Gear that they do not Know How to Use
I can't tell you how many times someone asks me what lens I used to photograph a particular subject. Then, they will turn around and buy that lens and ask me why they have soft images. The camera and lens are tools that we use to get our job done. You can go to the hardware store and buy a Milwaukee saw, but that won't make you a great carpenter. Now, mind you, having good equipment does remove that aspect from the equation. You will never doubt the equipment, but that equipment will not in and of itself improve your game.
Honestly, I recommend starting out with an older camera and a medium telephoto lens. Learn to master these tools along with proper technique and then move up to the big leagues. There is absolutely nothing wrong with this approach and if you find out you don't like wildlife photography, you are not out a ton of money. Technique, knowing your subject, and practice are the keys to taking all this to the next level, and there is no moment when you have mastered photography. It is always a learning experience.
#7 - Ignoring the Wildlife Shots in Your Area
Many who are just getting started in wildlife photography have the idea that they have to travel to some exotic location to take great shots. Although traveling to places like Yellowstone and Antarctica will give you exposure to some great wildlife, you can make great images in your own backyard. Even in large cities, there are parks which hold squirrels and birds. If you can afford to travel to exotic locations then by all means do so, but don't let location keep you from creating photographs. Don't use location as an excuse! If all you have are pigeons and squirrels then become the best pigeon photographer in the world. Whatever you do, don't stop shooting. The nuthatch image below was taken in my backyard using my van as a blind.
#8 - Failure to Understand the Basics of Photography
Do you know what shutter speed, ISO and aperture have in common? If you are dumbfounded by these basic elements of the exposure puzzle, then you will never make a great wildlife photographer. The reason for this is that light changes frequently and not only that, the reflection of light off our subjects further changes the equation. Not knowing the basics of exposure is a deal breaker! Get out there, read blogs, watch YouTube videos and practice! In the modern era there is a wealth of information on the internet. I had to get a degree with an emphasis in photojournalism back in the mid-90s to get a basic understanding, but in today's world, you don't have to, and so there is no excuse for ignorance.
#9 - Failure to Understand Light
This is a principle which took me a long time to get and sometimes I think I still don't get it fully. Thankfully, understanding light in wildlife photography is a bit simpler than understanding how to be a great strobist like Joe Mcnally.
First, as with most nature photography, there are two types of lighting that really make the difference. There is morning light and afternoon light. High noon is right out unless you are shooting on an overcast day. In the morning you want to shoot generally between sunrise and 9:30am. In the afternoon, you want to shoot about two to three hours before sunset all the way to sunset. During these times, the light is softer and because it is low to the horizon it produces a nice golden look. This is most often what you see in high quality photographs.
There is one more important consideration. Generally, you want the light coming from behind you and lighting the front of the subject. This really makes the feathers of the bird pop and gives the animal a specular highlight in the eye. It can really make your subject come to life. Beautiful morning light made this elk come to life.
#10 - Failure to Practice
We have all heard the adage "practice makes perfect" and with good reason. As it turns out, practice does actually do us a great deal of good. Do you practice often? Wildlife photography practice can be done very easily. If you have a Walmart parking lot, then you have a good subject. They are called gulls and they make great subjects to keep your reflexes, exposure, auto-focus, and panning skills in tune. I recommend getting out about twice a month at a minimum to keep yourself from getting too rusty. Do you have a zoo? Zoos make a great, low pressure environment to both practice and create great images in the process. I go to my zoo about three times a year to check my gear and look for new techniques to improve my photography.