@Drache613
We have large birds (vultures, pelicans but also other shorebirds) readily visible from the windows, and over time he got used to it. I think he know that nothing can come through glass and one first must open, and we don't open for birds

However, I would not dare going outside with him without harness - not because of the birds might snatch him but because I could think he then really gets scared when there is no glass between and might try running off to hide. Like: down the balcony, or into a drain.