Ducks and geese do tolerate each other. Swans can be a bit pushy, but they will deign to allow other birds to use their pond.
If there are ducks, and a reasonable amount of ground cover, I'm surprised there aren't ducklings already. Crows are very quick to steal duck eggs, and ducklings, though, so if the sight of ducklings being carried off to become meals for baby crows offends you, you may like to manage the habitat to discourage crows.
Ducks are not particularly good mothers, and they lose ducklings all the time - to crows, they fall down drains, they get lost, mum jumps up a step they can't climb, you name it. However, the ducklings are very firmly imprinted, and will do their damnedest to get back to mum whatever she does. So if you pick one up, it will probably scuttle back to mum with no problems, as long as she is still in sight. The trouble is, she's quite likely to wander off completely unconcerned at you meddling with her children.
Ducks and geese are quite happy, too, to adopt other people's ducklings and goslings - they sometimes form quite large creches, looked after by a dominant pair (only mum in ducks) while the real parents hover in the offing and trying to help look after them. If you find an abandoned duckling, point it towards the nearsets party of ducklings you can find, and it will probably latch on to them and be accepted.
Geese are quite good at dumping their eggs in their neighbour's nests. This explains the occurrence of canada geese paired to greylags - they grow up thinking they're the wrong species.
Your lakes won't become overcrowded. When it gets too busy, newcomers will come and check it out and go on elsewhere.
And, cruel as it may sound, the environment will only support so many animals. When the population gets too large, some will die (or fail to breed) from lack of resources, thus restoring the balance.
(This last bit of info is Population Ecology 101 in a nutshell, and something politicians would do well to learn about).
I have on today a blue self-striped collared shirt, and a sort of purply fleece pullover. But I do have the obligatory check shirt to go with the agricultural trousers.
I'm also hoping one day to blag one of those John Deere boilers suits that are so popular with the modern tractor driver.
Anyway, is there a brew on?
). 
This where it all started, with me asking if Landslide had worn his checked trousers on Wednesday night. 
