Mosquitoes hatch in water, but the amount needed is very, very little. If you have ponds, use mosquito dunks or get mosquito eating fish (there are several types). My understanding is that muscovies LOVE mosquitoes, but I've never had muscovies, so I cannot give experiential data on that. There are a number of pesticides that are effective on mosuqitoes; some are fairly long term, others pretty short term. Clear away brush where they tend to congregate, there are time released sprays that contain permethrin and are effective in controling mosquitoes in a smaller area. Country Vet is one brand name, but there are others. The Freshmatic Ulta (1/3rd the price) unit will work with these canisters, but you need to switch sprayer caps. Any sort of mosquito repellant will work for some amount of time.
Also, mosquitoes carry illnesses--not just to humans, but to many other creatures, including chickens, cats, dogs, horses, ... Some of these illnesses are serious, even fatal.