occasionally; once in a while; now and then; rarely; seldom
occasionally; once in a while; seldom; casually; unexpectedly; accidentally
occasional; infrequent; rare
coincidentally; by chance; unexpectedly; rarely; unusually; seldom
once in a while; occasionally; seldom; at long intervals
on rare occasions; once in a blue moon
lesser cuckoo (Cuculus poliocephalus)