Call census of Japanese Green Pigeons using timed voice recordings at Komayama, Oiso Town

<p>SUMMARY From April 30 to November 20, 2017 (199 days)t he calls of Japanese Green Pigeon, which flew to Terugasaki to drink sea water from the 2km north hillside of Komayama (el. 60m), were recorded from 30 min before sunrise to 5 hours after sunrise (5 hrs and a half) with an IC recorder. There were 21 days out of the 178 that could not be recorded due to noise disturbance from wind and rain. We analyzed the number of calls and also the calls of juveniles that were recorded over 164 days</p><p> 1) During the survey period of 178 days there was a total of 15,209 “oao” calls. An average of 85 times a day. </p><p>2) There were two peaks of “oao” calls during the survey period, at the end of May and the middle of August, and increases and decreases were observed between the peaks. A considerable decrease was observed after the second peak.</p><p> 3) There were more calls on sunny days than on cloudy/rainy days. The pattern of increase and decreases during the survey period showed the similar trend.</p><p>4) The earliest onset of calls was on Sept. 11 (24 min. BINOS vol.25（2018） before sunrise). With the exception of the end of May and November when the number of flying is less, the average onset time of calls on sunny days was 7 min. before sunrise. On cloudy/rainy days the average onset of calls was 11 min. after sunrise.</p><p> 5) It was observed that the number of calls increased 2 hours after sunrise and decreased after 4 hours.</p><p> 6) During the survey period the “popopo” calls could be heard 3 times. </p><p>7) The increase and decrease in the number of birds flying to Terugasaki and the number of “oao” calls until the beginning of September coincide. There was a continued increase in the number of flying birds from the end of August to around Sept 11, however, the number of “oao” calls showed definitive decrease after August 25. </p><p>8) Calls are broken up into 4 groups. Standard “oao” calls and unique characteristic calls type 1-3.</p><p> 9) Of the total 15,209 calls, 99.07% were standard calls. </p><p>10) Type 1 calls were long, muffled distressful sounding calls considerably out of the entire pitch which didn’t conclude at the 10th phrase. (total times 0.22%) </p><p>11) Unlike type1, type 2 concluded till 10th phase and out of 10 phrases over 40-70 % were unmusical distressful calls that were not muffled. (total times 0.26%) </p><p>12) Of all 10 phrases of type 3, less than 30 % of the phrases were an unmusical distressful call. Other than this there was nothing else different from the standard calls. (total times 0.45%) </p><p>13) Type 1 was observed at the end of July which coincided with the appearance of juveniles at Terugasaki. The call was fairly incomplete therefor it is thought to be that of juveniles born that year. </p><p>14) It was assumed that the type 2 calls after May 31 were not those of juveniles of that year. The calls were incomplete and thought to be the previous year’s juveniles</p><p> 15) It is possible that Type 3 calls are those of birds born in the previous year and that type 2 were those born in the same year but before evolving to type 3 which occurs from the beginning of their first summer (2nd year).Both calls may have changed to standard calls in the autumn. </p><p>16) It is assumed that when juveniles born in this year call in type 1 calls, not all the individuals call but only some of them do in incomplete manner. </p><p>17) Type 2 and 3 calls, which are assumed to be those of birds born in previous year, increase as the number of flying birds to Terugasaki increases. However, ratio of two types were only 1.2% of entire calls at most. It is possible that either a part of individuals born in previous year call or most of them call in standard call from the beginning of their flying to Terugasaki.</p>