Yes, is the short answer, ducks will start laying from about the end of February - sometimes earlier. If they 'quack' they are female, if they squeak they are male - youngsters are difficult to tell apart, but if these are mature their voices should tell you what sex they are. If you have one of each and want to hatch their eggs be careful as they may be brother and sister, you could get deformed chicks, and ducks are not known for being good parents. Personally, I'd eat the eggs and buy in young females.