If your boxer isn't fixed it could be having hormone problems that they especially get as a breed. Drooling can also be part of hormone problem. both problems could be from some female dogs going into heat were you can't see but he can smell. boxers as a breed especially when over heated, get excited or stressed, excessively pee drool and shed, and drinking a lot of water could go along with that. could be nutritional too from what he/she eating. your dog would probly love to clean up the duck poop and good for dogs as long as ducks healthy.
Ducks aside from muscovy (a domestic breed of wood/tree duck species), other domestic ducks (breed variations of mallard species), ducks will need a LOT of water that they will get filthy quick and everywhere just as quick. Mallard breeds of ducks need enough water to bath in every day to stay healthy, supposedly.
Ducks are prone to hardware poisoning as they supposedly love to eat metal. they get bumble foot as have apparently sensitive feet, and can get sick and die from medicated chick/en feed. "Crested ducks" are just genetic deficiency that started in commercial peking ducks (large meat and egg duck), and now bred into other domestic mallard breeds as well, that looks cute, but usually bad for bird possibly killing it, and any hatching you would want to do from them.
you sound as if runners taking up least space as supposed to look like bottle with head tail and feet standing straight upwright. giving eggs every day depending on who you get from (show vs traditional breed), and foraging supposedly well eating flies ect too, would be best for you, though some can be nervous and loud, but bred with tiny wings so cannot fly at all.
there are two types of commercial laying duck one white layer, one gold sex link "hybrid". both supposedly lay at least three hundred eggs a year, mature to point of lay and butchering early, and eat less. they are only good for few years as layers then stop and need replacing, supposedly.
Khaki campbells bred as all purpose duck from runner mallard and meat duck, Welsh harlaquine is just color form of KCs that got bigger for show. WHs are BOP magnets i hear from many. KCs supposedly lay longest of layer ducks. one here has one, her oldest, claims is still laying at age 14, when posted.
Muscovy are friendly and quiet being best urban ducks foragers eating plants bugs rodents, really anything they can catch and take apart to shove down throats. they need only enough water to put whole heads under water and shake out to clean nares (nostrils) eyes ears mouth and throat, so do not choke ect. males get goose size, seem scary and ugly (caruncles on face ect.) to most non duck or bird people, hiss and have a naturally larger Mohawk type crest than the females usually. both sexes not to cold tolerant like other domestic ducks are (forty degrees is as low and happy as mine go without needeng extra to keep warm). scovy also can and may fly.