We all grew up seeing only really good images of animals in publications and books or galleries so did not see the millions of not so great images taken by everyone else that had no means of distribution. It was almost as if animal or bird photos were easy because all we saw were good one. We knew it was hard to take good photos of family and friends, because we saw the results of those all the time. The whole point of some of the well considered advice given in this threat has been "field craft" which has everything to do with good photos and very little to do with taking photos.
It is not just luck that some people get enough keepers that people want for magazine covers or printed large over the fireplace. In just about every field where attention to detail, subject knowledge and creative problem solving separates the norm from really special, the easiest part is the equipment that is getting easier and easier to buy and use than ever, and the hardest is intimate subject knowledge. Most people who excel in anything learn enough about the subject, or discover enough to help their goal. So in this case, find the subject species you are fascinated by and read everything you can get your hands on, both technically and folk writings or oral histories. Spend a lot of time watching, learning habits that are common to all, and those traits which appear to be expressed individually. Learn their feeding, courting, resting, and hunting habits, the range and hours of activity. Soon or not so sooon but eventually, you will be able to guess with better and better accuracy as to where to be before they show up, or when to catch them where they are more relaxed and less wary. Knowing what they are likely to do next is much better than being lucky. That is the hard part and what few people have the patience to master. There is no rule book or set of instructions so being an effective observer further separates your access to the birds from that of the typical chance shooter. If you are close, everything gets better and equipment demands drop. There are some observations that will require adjustment to how someone is probably doing it now. For example the mere act of looking for and at birds or any animals, humans included, is noticed and noted by the observed. If you can refrain from looking at them, and just go about your business you will be ignored. We, and almost all animals with complex eyes, are very sensitive to other eyes. We know or sense when someone is looking at us even it in a crowd or in a busy background. It there are animal eyes looking at us as we sit around the camp fire, we know it very quickly, and looking back is often enough of a confrontation to ward off any hostile actions, or it can provoke and challenge the spy. We are wired as a key survival aid to spot eyes looking at us even if they are a tiny proportion of a complex general scene of background. So, avoid looking at them with uncamouflaged eyes. Camera lenses create a much less dramatic reaction, if noticed at all.
Your 70-300 lenses are fine if the subjects are larger or you can get close but a lot of things work against good images at a great distance. The air itself is a problem, with haze, thermal distortion and particulate matter that work against razor sharp images. You lens can out resolve the air between you and a target 300 meters away, just as an example. The good news is that learning field craft is fun and cheap. The bad news is that it take real patience and study over a long time. A good way to get up the learning curve is to not take your camera so you are not distracted and can remain attentive to the subject. Good luck and have fun! Stan St Petersburg Russia