Easton's Bible Dictionary (1897)
In our Lord’s time the Jews had adopted the Greek and Roman division of the night into four watches, each consisting of three hours, the first beginning at six o’clock in the evening (Luke 12:38; Matt. 14:25; Mark 6:48). But the ancient division, known as the first and second cock-crowing, was still retained. The cock usually crows several times soon after midnight (this is the first crowing), and again at the dawn of day (and this is the second crowing). Mark mentions (14:30) the two cock-crowings.
Matthew (26:34) alludes to that only which was emphatically the cock-crowing, viz, the second.
Hastings' Dictionary of the Bible (1898) & Schaff's Bible Dictionary
COCK'-CROWING. Mark 13:35. A name given to the third watch of the night, from midnight to daybreak. " To reconcile this seeming variance, it is stated that there were two cock-crowings -one soon after midnight, and the other about three o'clock- and that the last, which was the signal of approaching day, was spoken of as the cock-crowing. To this it has been answered that only one hour elapsed between the denials. Luke 22:59. This is true of the second and third, but there seems to be no authority for saying it is of the first and second.
" Both referred to that cock-crowing which especially and most distinctly marked a watch or division of the night. , and only an incidental one in the New. Matt 23:37; Luke 13:34. Some suppose that poultry were introduced into Judaea by the Romans.