"The ethical dilemma makes it clear though; a few mice out of billions to perhaps allow the gene pool of the owl to remain viable."
The ethical dilemma would be more real if there were serious proposals to reduce the harm humans cause to the owl population in the first place. Traps, gunshot, road hits and pylons. All of these could be significantly reduced if we took the 'ethical 'problem more seriously. But the oohing and aahing over the beauty and cuteness of owls gives the game away over those moral values that along with existing brutality (predators) by those that have no choice in the matter hey presto justify a bit more violence from those (us) who do.
The plants comparison is a non-argument, not least as there is no better choice in the matter. But also, coming as it invariably does from meat-eaters - as their other arguments are based on a different sets of values, it's not credible that they can be concerned about plants.