If the storms caused a high mortality of the ducks on Saturday night, what assumption has been violated and how would this affect our population estimate?

The question seems to be referring to the assumptions of the Lincoln-Petersen index, a method used in ecology to estimate population size. One of the key assumptions of this method is that the population is closed, meaning no immigration, emigration, births, or deaths occur between the time of marking and recapture.

If a storm caused a high mortality of ducks on Saturday night, this would violate the assumption of a closed population because deaths have occurred.

This would affect the population estimate by making it artificially high. The reason for this is that the Lincoln-Petersen index calculates the population size based on the proportion of marked individuals in the initial sample to the proportion of marked individuals in the recapture sample. If many of the ducks died due to the storm, the proportion of marked individuals in the recapture sample would be higher than it should be, leading to an overestimate of the population size.