“I observed ~ 100 House Swift (Apus nipalensis subfurcatus) nesting under an overhead bridge/road in the city early in the morning. The adults were actively feeding juveniles and were very 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.
“The sonogram and waveform of two such thrills with crescendo-decrescendo elements (best seen in the waveform) are above and below. 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 shows how 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.
Dato’ Dr Amar-Singh HSS
Ipoh, Perak, MalaysiaIpoh, Perak, Malaysia
12th May 2019
Location: Ipoh, Perak, Malaysia
Habitat: Urban environment