Main lesson of birdwatching isn’t it: wait and watch and then wait some more. 
I’ve been very interested in the Egyptian geese on the lake for the last few years, specifically what happens to all their chicks. Took until this year for me to find out, when I watched a mother take her very small chicks out onto the lake (much smaller than I’ve ever seen them in the water before). She confidently swam them up to a black-backed gull, who promptly took off, grabbed one of the chicks and then flew off with it. So the reason that Egyptian geese have so many chicks and the reason not many of them survive very long is that Egyptian geese are pretty damned stupid.