YOU DON'T KNOW HOW LUCKY..........
I was a teenager when I first got into bird photography, as a means of recording what I'd seen, but then it almost became an end in itself. The first camera was a Petri Flex5 SLR, with a Hanimex 400mm F6.3 lens. I don't think I bought the standard lens for it 'til later. The telephoto had a pre-set diaphragm, so you had to decide on the aperture before the shot, but anything above F8 and the image was too dark for the manual focussing. There was no in-camera exposure meter, so you had to rely on a hand held one, which didn't always tally with what the lens was looking at. Usually, by the time you had sorted out exposure, focus and framing, the bird was long gone. Eventually the lens diaphragm collapsed, so it became junk. I upgraded to the "in" camera at the time, a Pentax Spotmatic, which had built-in through the lens metering, and a Dallmeyer Adon 14 inch F4.5 lens (equivalent to about 350mm) - a British product, believe it or not. It was robust and sharp, reasonably priced (I couldn't afford the equivalent Kilfitt model!) and I still have it. I eventually progressed to the Canon A system, and onward to the EOS cameras, the digital derivatives of which I use now.
The films of the day were still dominated by black and white negative stock, which I developed myself. Judging by the amount of dirt on the negatives, I must have used water straight from the nearest ditch. Colour print film in the 1960's was dire to say the least. Slide films were limited by their speed. Kodachrome 25 was best for colour, but too slow (at ISO 25) for birds. Kodak High Speed Ektachrome at ISO 160 was reasonable, but colour saturation wasn't great, and it had very poor exposure latitude of about half a stop. There was an American brand called Ansco, at ISO 200, but was virtually devoid of colour and had grain the size of golf-balls. Eventually, decent high speed colour slide stock came along with Fuji.
My first ever photographic outing was to Filey Brigg, where, unbelievably, there was a Grey Phalarope, of which I got some pictures - a bit "dot in the distance", but I was hooked.
Here are one or two B&W golden oldies - heavily digitally manipulated from scanned negatives! They were all taken around the late '60's, early '70's.

Guillemot, Bempton. This was a Dallmeyer shot.

Flight photography was very hit and miss. You pre-focussed at a distance that would give a good image size, and then tracked a bird in the hope that it would fly into focus - then you relied on your reflexes to get a sharp shot before it flew out of focus. You wasted a lot of film!

Kittiwake, Filey Brigg. A Hanimex shot.

Red-backed Shrike. Filey CP. Another Dallmeyer picture.

Red-breasted Merganser, Scarborough Harbour. Dallmeyer lens.

Most birds needed to be tame, or you needed a hide to get close.

All of the above nauseating nostalgia serves to demonstrate how technology has moved on, with today's digital, auto-focus, auto-exposure, image stablised, high ISO gear making it easy for anyone who can press a button to get acceptable bird pictures.