ML158358311

観察結果の詳細

Species: House Swift Apus nipalensis subfurcatus – nesting colony Location: Ipoh, Perak, Malaysia Habitat: Urban environment Date: 12th May 2019 Equipment: Nikon D500 SLR with Tamron SP 150-600mm f/5-6.3 Di VC USD, handheld with Rode VideoMic Pro Plus Shotgun Microphone Remarks I observed ~ 100 House Swift nesting today. Their nests were located under an overhead bridge/road in the city that was largely inaccessible to humans. There were large numbers of nests, scattered over a wide area, but some were taken over by other birds. The House Swifts used to nest in buildings in the city but in recent years shop owners have been destroying the nests to discourage the birds. They nest in colonies and Wells (1999) describes it aptly as “neighbouring nests overlap to form continual, irregular ‘village’ clusters …”. Post 1 shows one such ‘village’ cluster which houses at least 5 different birds. Even a small nest structure as shown in post 2 housed three different pairs. Lighting was poor under the bridge but I could clearly see many juveniles waiting at the entrance holes to be fed; the white of their chins & throats showing strongly (see Post 3 of a juvenile). Post 4 shows an adult resting. Note the marked streaking of the rump and chin which is said to be prominent in A. n. subfurcatus (HBW 2019). Feeding of juveniles was active in the early morning (8-8.30am) with adults vocally active around nests with thrills and screams. The thrills are a done communally with many birds singing out together, gathering into a crescendo and down again. When 30-50 birds do it together it can be quite loud under a large bridge. A composite recording made from 2 different recordings is here: https://www.xeno-canto.org/473886 The sonogram and waveform of two such thrills with crescendo-decrescendo elements (best seen in the waveform) are in post 5 and 6. I am not able to clean the background sounds (cars, occasional Starlings and dogs) as calls are made almost continually by some birds. The sonogram show wonderful these calls are – very high frequency and stacked in uniform layers of 3-4khz, spaced very regularly, packing 13-16 calls in a second. The rising and falling nature of the group calls is created by more bird joining and then withdrawing as a peak is reached. Amar Amar-Singh HSS (Dato' Dr) Ipoh, Perak, Malaysia