Cuckoo.

Cuckoos are insect-eating migratory birds that appear in Israel during the summer. Scholars feel that the Hebrew word was incorrectly rendered cuckow in the KJV. There is no obvious reason why the cuckoo would be considered an unclean bird (Lev. 11:16; Deut. 14:15). The NKJV translates “seagull.”

Source: [Anon-Animals]

(Heb. shahaph), from a root meaning “to be lean; slender.” This bird is mentioned only in Lev. 11:16 and Deut. 14:15 (R.V., “seamew”). Some have interpreted the Hebrew word by “petrel” or “shearwater” (Puffinus cinereus), which is found on the coast of Syria; others think it denotes the “sea-gull” or “seamew.” The common cuckoo (Cuculus canorus) feeds on reptiles and large insects. It is found in Asia and Africa as well as in Europe. It only passes the winter in Palestine. The Arabs suppose it to utter the cry _Yakub_, and hence they call it _tir el-Yakub_; i.e., “Jacob’s bird.”

[Easton]

shachaph; Lev 11:16; Deu 14:15; unclean. Rather the Greek cepphus of Aristotle, a large petrel, as the Puffinus cinereus. From a root “to be slender”, “light of body” like a gull, whose body is small compared with its apparent size and outspread wings; it skims the waves, seeking its food in the agitated water. Andouini’s gull, abounding on the shores of Syria (Tristram), a more likely bird than the storm petrel, which is seldom seen on land.

[Fausset]

(1):

kook’-oo, kuk’-oo (shachaph; laros; Latin Cuculus canorus): The Hebrew root from which the word shachaph is derived means “to be lean” and “slender,” and in older versions of the Bible was translated cuckow (cuckoo). It was mentioned twice in the Bible (Le 11:16, and practically the same in De 14:15 the King James Version “cuckoo”), in the list of unclean birds. The Latin term by which we designate the bird is very similar to the Arabic, and all names for it in different countries are so nearly the same that they prove themselves based on its double cry, “cuck-oo,” or the single note “kowk” or “gouk.” The bird is as old as history, and interesting because the European species placed its eggs in the nests of other birds, which gave rise to much fiction concerning its habits. The European bird is a brownish gray with white bars underneath, and larger than ours, which are a beautiful olive gray, with tail feathers of irregular length touched with white, knee tufts, black or yellow bill, according to species, and beautiful sleek head and shining eyes. Our birds build their own nests, attend their young with care and are much loved for their beauty. Their food is not repulsive in any species; there never was any reason why they should have been classed among the abominations, and for these reasons scientists in search of a “lean, slender” bird of offensive diet and habit have selected the “sea-mew” (which see) which is substituted for cuckoo in the Revised Version (British and American) with good natural-history reason to sustain the change.

Gene Stratton-Porter

(2):

kook’-oo, kuk’-oo (shachaph; laros; Latin Cuculus canorus): The Hebrew root from which the word shachaph is derived means “to be lean” and “slender,” and in older versions of the Bible was translated cuckow (cuckoo). It was mentioned twice in the Bible (Le 11:16, and practically the same in De 14:15 the King James Version “cuckoo”), in the list of unclean birds. The Latin term by which we designate the bird is very similar to the Arabic, and all names for it in different countries are so nearly the same that they prove themselves based on its double cry, “cuck-oo,” or the single note “kowk” or “gouk.” The bird is as old as history, and interesting because the European species placed its eggs in the nests of other birds, which gave rise to much fiction concerning its habits. The European bird is a brownish gray with white bars underneath, and larger than ours, which are a beautiful olive gray, with tail feathers of irregular length touched with white, knee tufts, black or yellow bill, according to species, and beautiful sleek head and shining eyes. Our birds build their own nests, attend their young with care and are much loved for their beauty. Their food is not repulsive in any species; there never was any reason why they should have been classed among the abominations, and for these reasons scientists in search of a “lean, slender” bird of offensive diet and habit have selected the “sea-mew” (which see) which is substituted for cuckoo in the Revised Version (British and American) with good natural-history reason to sustain the change.

Gene Stratton-Porter
[Fausset]

Cuckoo,

shachaph. Only named in scripture as an unclean bird not to be eaten. Some have supposed that a marine bird is alluded to: the R.V. has ‘seamew.’ There are however cuckoos in the land, and called also by that name, because of their cry. Lev. 11:16; Deut. 14:15.

[Morrish]