"of or pertaining to ornithology, relating to the study of birds," 1763, from ornithology + -ical. Related: Ornithologically.
Entries linking to ornithological
ornithology n.
"scientific study or knowledge of birds," 1670s, from Modern Latin ornithologia (1590s); see ornitho- + -logy.
-ical
compound adjectival word-forming element, usually interchangeable with -ic but sometimes with specialized sense (such as historic/historical, politic/political), Middle English, from Late Latin -icalis, from Latin -icus + -alis (see -al (1)). Probably it was needed because the forms in -ic often took on a noun sense (for example physic). Forms in -ical tend to be attested earlier in English than their twins in -ic.