I got into wildlife and bird photography at about the same time as photography in general — helped along by Jane's genuinely encyclopaedic knowledge of birds, and the mild embarrassment of not knowing the common garden ones half as well as I should have.
Like most beginners, I blamed the equipment. Somebody else's photograph would have exquisite feather detail and colour, mine wouldn't, and the easy fix was obviously a better camera. Over the following decades that turned into a fairly undignified round of upgrades and manufacturer-hopping: Sigma, Sony, Nikon, Olympus, and back to Sony again.
What actually causes a blurry bird photo
There are more ways to get this wrong than right: a shutter speed too slow for the bird's movement, a lens pushed past what it can resolve, being far enough away that the bird only fills a tiny corner of the sensor, or cranking the ISO until noise drowns the detail. I have — had — many, many examples of all four. Most have since been deleted from a photo library that, last I checked, was comfortably past 80,000 images.
A couple of turning points
One was buying a secondhand Nikon D3S — "only" 12 megapixels, but with colour rendering that still holds up, and a light sensitivity good enough that I'd happily shoot at ISO 12,800 without a second thought (I wouldn't dare try that with my current body). That camera was paired with my first genuinely good lens, a Nikon 300mm f/2.8, usually with a 2x teleconverter attached.
None of it made me a good photographer overnight. But it's the reason the byline on this site still says "solar-powered bird photography," years and several camera bodies later.