@Ebirah766 I had the same thought going through these photos. It seems their goal these days is: "how can we make fencing standout as much as possible". Did zoos back then also plant immature foliage for new exhibits and hope for it to look natural decades down the line?
No shade and barely even any foliage - certainly not what I would expect for a songbird aviary. It will hopefully look better some years down the line, but I can't imagine the birds are all that comfortable right now...
@Moebelle to be fair it’s very expensive to bring in full size trees so it’s rarely done. That being said you can still spec larger trees than they did here without too much heartache.
But how often are existing trees cut down for construction?
And there are also good temporary solutions: For example, fast-growing grasses such as bamboo. Or vines, climbing plants, etc. provide shade and a natural atmosphere in a short time.