It is the principal aim of my experience to examine what mechanism the cocks' crowing at the early dawn is based on.
For this purpose a couple of genuine white leghorns was chosen, from whom were gained more than 20 eggs, and they were hatched.Among them only the cocks numbering 12 were bred and used for the experimental material. These 12 cocks were slowly separated from one another until each one of them was bred by itself. Putting these individuals under the entirely same condition from the time of chickens, I examined the results of the following three experiments.
1) Changes of vocal sound as each individual becomes older.
2) Comparison in normal crowing between separation and cohabitation.
3) Comparison in normal crowing at the early dawn between the normal cocks and the deaf cocks.
Now, this article is the conclusion which I have arrived at in the experiments.
By the way the deaf cocks are those which when 200 days passed after their hatch were bored a hole in the tympanum of their ears after complete sterilization and the holes were filled with guttapercha used in dental surgery and then their burr edges were closed with three stiches.
1. Under the same experimental condition, the age when the cocks utter for the first time is 142 days on the average.
2. Each of the cocks does not give its first utterance except in the morning. The first utterance can never be heard in the afternoon, still less in the evening.
3. The sound of voice in the first utterance is divided into a voiceless and a voiced sound. Then a change takes place when they begin to crow in normal note.
4. The note of first utterance is generally “kc : ”, while some of the cocks rarely utter in the note of “kc : c” and others in “kcc : c”.
5. The note in normal crowing is “kcke kc kcu.” The sooner the cocks can utter these two underlined assimilated sounds, the smaller is the number of times of their change of note from the first utterance to normal crowing. The smaller is the number of times of vocal change, the more rapid is its process.
6. The days tend to become more and more from the first utterance to normal crowing, the more are the days to be spent between the hatching and the first utterance.
7. The more are the days from the first utterance to the normal crowing, the smaller is the number of times of vocal change.
8. The days to be spent from the hatching to the first utterance, and the days from the first utterance to normal crowing ; the gaining in weight and the lengthening of the cockscomb-between these things there can be seen no remarkable relation. Neither the cocks' growth by the day nor the gaining in their weight has anything to do with the number of times of normal crowing. The hours of normal crowing, however, have a close connetion to the growth by the day.
9. As for the number of times of normal crowing in a day, there are some individual differences among the cocks coming out of the same parents, but the number of times that each one of them crows for itself is almost constant. The length of daytime, however, has a great influence upon the number of times of normal crowing. For this reason the number in June whose days are long, is larger than that of November. But the number of times at the early dawn is not related to any season. Another thing is that on the whole the number of times is distinctly smaller in cohabitation than in separation.
10. The number of times of normal crowing is small for a certain while before and after noon, and the number becomes smaller and smaller towards evening. In the evening the cocks utter frequent crows periodically at a single time, and the stop crowing at sunset. These frequent crows are uttered at the same hours in case of “brother-cocks”.
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