Not aware of any problems, but if they took the odd chick I would be unlikely to notice.
Still seem to breed plenty of finches, so I doubt the predation rate for this species is high.
Back to Dettol, from Wiki
"Chloroxylenol is not significantly toxic to humans, is practically non-toxic to birds, and is moderately toxic to freshwater invertebrates. It is highly toxic to fish, cats, and some amphibians and should not be used around them"
The toxicity to cats should make RodL happy, but no mention of reptiles

Given that birds are just the modern reptiles, I think it is unlikely to be effective.
Cheers
Brett