Steps to reproduce (following the documentation):

query.author

resT1 <- cr_works(query = "ecology", flq = c(query.author = 'Boettiger'))
noResT1 = resT1$meta$total_results

query.container-title

resT2 <- cr_works(query = "ecology",
flq = c(query.container-title = 'Ecology'))
noResT2 = resT2$meta$total_results

These searches give exactly the same results, suggesting the 'flq' term is not working.
Since the 'query' field only allows for OR logic, it seems that no AND logic is possible.