the blue headed one is the male and the dark brownish one is the female
if you see him and don't see her, he is at guard and she is either foraging for bugs or sitting falsely possibly ( she may have lost her original nest in early April to predators and mother nature is fooling her into thinking she needs to start another) (although it is late for them, our ducks on the lake are already half grown),
the pool is not a good environment for them - the chlorine - if you want them to adopt the pool this year you need to stop treating the water so it become tolerable for them - green for you
if you purchase cracked corn and put it in a heavy pie tin and set it next to a fresh deep dish of water close to the pool they will eat it - feed them once a day at the same time about a cup for each bird
loosely scatter hay around where the male was resting - they will gather it to where she wants it to nest one way or another ( real or false nest)
don't be tempted to feed them store bought white bread - it isn't good for them - they can have 12 whole grain bread - no salt or low salt - that is much better for them - and yes you can "tame" them enough to eat from your hand - but be aware that when they migrate they will think all humans are as kind as you and paddle up to a hunter during season and become someones dinner - we don't tame them anymore after seeing that happen on our own lake - now we just use pans to feed them -
keep doggie away from them if at all possible - she can look at them through the window also - dog is duck natural enemy, whether dog knows it or not - duck will not tolerate dog for long before it chooses to leave for a no dog yard -
at this stage they may still be flightless - molting for the summer - that is why they didn't fly when dog walked by - they are vulnerable - the brown one will hide as much as possible -
install your duck pond after migration this year - october/november - they will find it next year if they choose to return - if she does have a clutch of eggs and they hatch the babies if they survive will return to your yard because that is where they hatched
all you can do is what i suggested and look for them every day and night - if they choose to adopt you they will - but they have to feel safe - that means no doggie, unfortunately, doggie can have another part of the yard
if you are fortunate to see their nestlings - they are the absolutely most adorable little things you have ever seen -
http://www.youtube.com/watch?v=QY3re1GK3Ms
here is a video from you tube of another fella and his experience with mallard ducklings and momma duck
i only watched day one - you can finish for me
good luck