Last Saturday a Mallard Hen appeared in our pool with 8 ducklings. Looking online & local wildlife info ph line - we followed directions to let Mama duck do the job 100%, fill one pie tin with water. (Chg this out daily) and to make a ramp for the ducklings to easily exit the pool. We did all of this. Also not to shock the pool with chlorine, but any already in it wouldn't be of a harmful consequence. By Monday the Hen was just keeping her brood under her at the edge of the pool ramp at night. Yesterday we found 2 dead ducklings where they'd all been sleeping. This am 1 more. I called the info line they told me what feed to get to put in a pie tin in their vicinity. Got it. When I came back all the ducklings were dead , except 1 and that 1 was kind of lethargic, leg twitch now and then. Matter of 1/2 hr and then still. Just laying on their sides. They'd all seemed to have great stamina every day, yesterday (before finding the first two) last night and then even earlier this morning - swimming and waddling around. I know no one can know for sure, but could it have been bacteria, disease, hypothermia? Any input? After my husband netted the last duckling over to our planters the mother flew away immediately.