I will give my opinion on this and some other information. First off, is the pound really land owned by the state, like a park? Are you sure it is not someones pound that they have opened to the public? I ask this question because I am pretty sure that the city only stocks park ponds & lakes with native species of ducks, most often the mallard. If this is a park pond then those ducks were likely not put there by the park and were ditched. If that is not a park pound and is just someone's pond open to the public then the owner most likely released the ducks there. What climate do you live in, if it is a cold one, like Wisconsin, then those ducks would all be dead in the winter if they were not being cared for by someone. If you live in a cold climate and see those ducks year after year then I bet that they belong to someone who is providing shelter during the winter months.
The Migratory Bird Treaty act does not protect domestic species but don't be mistaken, it pretty much protects every single species of native bird in the USA, migratory or not. One exception is the American Crow but that is just because they earned themselves a bad reputation as pests. Other than the crow almost every native bird is protected, this means you can not own any part of the protected birds or any product of the protected birds without a permit. You can not kill or own any of the protected birds without a permit. The crow is still protected by the act in every other way besides hunting because as said before it is a pest, you are still not allowed to own eggs or feathers or anything like that. If you do kill these bird or own these birds without a permit theeeen you get a punishment, it could be as small as a $20 fine or as big as a $200,000 fine and some jail time depending on what you are caught doing

Of course domestic ducks are not involved with this act at all, I just wanted to clarify some stuff up about this act because there was multiple wrong comments involving it. My comment may not even be 100% correct, it is pretty easy to be wrong

I'm pretty sure this act is used mainly to stop the trade/market for native birds and native bird products and stop the hunting of native birds without a permit.
There was more than enough rude/angry comments in this thread, calm down angry people, it is a question about snatching ducks from ponds, you can be angry but there is no need to show that in your comment

You can debate, sure, but just have a friendly debate
What type of duck is in the pond anyways? If you are in a southern state and you answer Muscovy duck then you have completely switched up this whole question and whole thread. I personally would not go taking baby ducks from a pond, that is to much work, baby mallard derived ducklings can dive under the water and shoot off like little torpedoes when spooked. Wood ducklings can swim so fast it appears like they are running on water. There is no way you will easily catch a baby duck unless you can do that food trap you are talking about. If I, for whatever reason, decided that I wanted a duck from the pond I would go and find the nest and wait till hatch day and then just use a giant net to snatch the whole family and leave no one behind, even this has the risk of injuries though
The problem that comes with taking baby ducks from mom ducks is that they share an extremely close bond that is formed before the ducklings even hatch, if you seperate them you will not break the bond, you will have a high chance of just killing the ducklings. Maybe if you took like 5 or 6 they would live, they also form a close bond with their siblings and can survive with the help of eachother. Another problem that comes with stealing ducks is they will most definitely hate you, after you chase them down and steal them from their mother they will forever see you as a predator. You might be able to gain their trust after a few years of not handling them and feeding them treats. I would still recommend just getting them from a hatchery, those ducklings never had a bond with anything besides there brood buddies. Hatcheries do not steal ducklings from the mom, they just collect eggs and incubate them, the mother ducks have no bond between them and their eggs.
So to conclude, I would say if it is legal you could take them but I would recommend not to because it will stress the ducklings, they will likely die, and if they do not die they will hate you for years after the capture. I would definitely recommend that you simply order ducklings from a hatchery, they will not be stressed if you get more than one then they will be happy. Also, those ducklings will not hate you and you can form a bond with them in a a few weeks or months. Hatching your own eggs is also a option.