1. Use the car as cover
Using cover is a great way to approach birds, and your car is one of those covers. Keep your camera within easy reach as you drive down a trail or into a scenic spot. Once you see an opportunity to shoot, simply roll down the window to shoot. Birds are generally not afraid to fly around cars unless you attack them.
2. Avoid sudden movements
Animals are very sensitive to your movements, so don't make sudden movements that might startle them. Even slow, calm movements can often startle them, so the option is to stay still and wait for them to fly towards you.
3. Don’t have extra actions
Some birds are brave and you can get close to them. An example is the white swan.
4. Move carefully
Many birds will keep you close as long as you don't make sudden movements.
5. Approaching quietly
Sometimes this trick really works, just make sure the bird doesn't see you, and you can sneak up on it and shoot carefully.
6. Get down, don't do anything
Birds sometimes approach you unexpectedly when you get down. Just find a good spot, or throw in some food, and be patient.
This technique is very useful if you want to photograph some cautious birds, or if you need to get up close and personal with smaller birds. You can use camouflage tape, camouflage nets, or something from your surroundings for camouflage. You can hide near something that preys on birds, or you can put some food where you want birds to show up. Sunflower seeds are often good food. If you want the bird to rest on the branch before eating, place the food under the branch.
Whichever way you choose, be patient. If you don't succeed once, don't look elsewhere. Sometimes a good idea is to come back the next day and try again.