In autumn 2021, in cooperation with Peking University and the Asian Infrastructure Investment Bank (AIIB), Birding Beijing set up a pilot project to record nocturnal bird migration over Beijing. From 25 August to 2 November 2021 we recorded audio every night, from sunset to sunrise, from the roof of the AIIB headquarters in central Beijing. The primary aim was to raise awareness of the scale of nocturnal bird migration over China’s capital, especially the volume and diversity of species that fly over the city as its residents sleep, recognising that awareness is the first step towards building pride and public support for policies and measures that protect these birds and the places they need.
We used a Wildlife Acoustics Song Meter Mini as it is weatherproof, capable of storing sound files for the whole period on a 512GB memory card, and programmable – automatically adjusting the recording time to account for the changing sunset to sunrise. The location of the 15-storey AIIB headquarters is ideal for recording nocturnal flight calls as it is situated immediately south of one of Beijing’s largest parks, the Olympic Forest Park, not close to any major road and free of air traffic.
We used Audacity, free-to-download software, to create spectograms of each hour-long audio file and used the ‘labels’ function to log and, where possible, identify each call. The label files were then imported into Excel to produce a database of all call events with associated date, time, number of calls and, where possible, an identification.
Summary of results
- 34,713 calls recorded
- Around 95% of calls identified to species or, in the case of buntings, flycatchers and thrushes, to family, with at least 60 species identified so far
- Most common calls were Olive-backed Pipit (12,411), Black-crowned Night Heron (5,358) and Eurasian Skylark (2,611).
- Five nights recorded over 2,000 calls (in order of volume`)
- 27/28 September (2,703 calls)
- 28/29 September (2,405 calls)
- 14/15 October (2,270 calls)
- 9/10 September (2,233 calls)
- 22/23 September (2,025 calls)
- The busiest hour-long file was 0502-0602 on 29 September with 1,012 calls
Rarities included possibly only Beijing’s 8th Grey-tailed Tattler Tringa brevipes 灰尾漂鹬 Huī wěi (piào) yù and at least two Little Curlew Numenius minutus 小杓鹬 Xiǎo biāo yù (not annually recorded in Beijing).
The graph below shows the volume of bird calls per night over the recording period.
The table below lists the species (or group of species) by volume of calls.
|Species||No. of calls|
|OLIVE-BACKED PIPIT Anthus hodgsoni 树鹨 Shù liù||12411|
|BLACK-CROWNED NIGHT HERON Nycticorax nycticorax 夜鹭 Yè lù||5358|
|BUNTING SP. Emberiza sp. 鹀 wú||4250|
|EURASIAN SKYLARK Alauda arvensis 云雀 Yúnquè||2611|
|COMMON ROSEFINCH Carpodacus erythrinus 普通朱雀 Pǔtōng zhūquè||2124|
|WHITE-EYE SP. Zosterops sp. 绣眼鸟 xiù yǎn niǎo||1566|
|"TSEEP" THRUSH SP. Zoothera sp. or Turdus sp. 鸫 dōng||909|
|FLYCATCHER SP. Muscicapa sp. 鹟 wēng||856|
|YELLOW-BELLIED TIT Periparus venustulus 黄腹山雀 Huáng fù shānquè||549|
|BRAMBLING Fringilla montifringilla 燕雀 Yànquè||329|
|EASTERN YELLOW WAGTAIL Motacilla tschutschensis 黄鹡鸰 Huáng jí líng||311|
|RICHARD'S PIPIT Anthus richardi 理氏鹨 Lǐ shì liù||266|
|RED-RUMPED SWALLOW Cecropis daurica 金腰燕 Jīn yāo yàn||252|
|SILVER-THROATED TIT Aegithalos glaucogularis 银喉长尾山雀 Yín hóu cháng wěi shān què||248|
|WHITE WAGTAIL Motacilla alba 白鹡鸰 Bái jí líng||204|
|SIBERIAN ACCENTOR Prunella montanella 棕眉山岩鹨 Zōng méishān shí liù||125|
|GREY HERON Ardea cinerea 苍鹭 Cāng lù||108|
|ORIENTAL MAGPIE Pica serica 喜鹊 Xǐquè||104|
|SIBERIAN RUBYTHROAT Luscinia calliope 红喉歌鸲 Hóng hóu gē qú||84|
|WINTER THRUSH SP. Turdus sp. 鸫 dōng||59|
|STRIATED HERON Butorides striata 绿鹭 Lǜ lù||48|
|PINE BUNTING Emberiza leucocephalos 白头鹀 Báitóu wú||46|
|GREEN SANDPIPER Tringa ochropus 白腰草鹬 Bái yāo cǎo yù||42|
|DAURIAN JACKDAW Coloeus dauuricus 达乌里寒鸦 Dá wū lǐ hán yā||33|
|PALLAS'S BUNTING Emberiza pallasi 苇鹀 Wěi wú||29|
|YELLOW-THROATED BUNTING Emberiza elegans 黄喉鹀 Huáng hóu wú||29|
|LONG-BILLED PLOVER Charadrius placidus 长嘴剑鸻 Cháng zuǐ jiàn héng||25|
|FOREST WAGTAIL Dendronanthus indicus 山鹡鸰 Shān jí líng||23|
|BUFF-BELLIED PIPIT Anthus rubescens (japonicus) 黄腹鹨 Huáng fù liù||19|
|CARRION CROW Corvus corone 小嘴乌鸦 Xiǎo zuǐ wūyā||18|
|GREAT BITTERN Botaurus stellaris 大麻鳽 Dà má jiān||17|
|SCALY-BREASTED MUNIA Lonchura punctulata 斑文鳥 Bān wén niǎo||15|
|LITTLE GREBE Tachybaptus ruficollis 小鸊鷉 Xiǎo pì tī||13|
|PURPLE HERON Ardea purpurea 草鹭 Cǎo lù||13|
|COMMON SANDPIPER Actitis hypoleucos 矶鹬 Jī yù||10|
|LAPLAND LONGSPUR Calcarius lapponicus 铁爪鹀 Tiě zhǎo wú||9|
|GREY-HEADED LAPWING Vanellus cinereus 灰头麦鸡 Huī tóu mài jī||8|
|LARGE-BILLED CROW Corvus macrorhynchos 大嘴乌鸦 Dà zuǐ wūyā||8|
|SPOTTED REDSHANK Tringa erythropus 鹤鹬 Hè yù||7|
|CHINESE GROSBEAK Eophona migratoria 黑尾蜡嘴雀 Hēi wěi là zuǐ què||7|
|BLACK-FACED BUNTING Emberiza spodocephala 灰头鹀 Huī tóu wú||7|
|COMMON [CHINESE] BLACKBIRD Turdus merula mandarinus 乌鸫 Wū dōng||6|
|LITTLE CURLEW Numenius minutus 小杓鹬 Xiǎo biāo yù||5|
|BROWN SHRIKE Lanius cristatus 红尾伯劳 Hóng wěi bóláo||4|
|BLYTH'S PIPIT Anthus godlewskii 布氏鹨 Bù shì liù||3|
|RED-THROATED PIPIT Anthus cervinus 红喉鹨 Hóng hóu liù||3|
|SNIPE SP. Gallinago sp. 沙锥 Shā zhuī sp.||3|
|GREY PLOVER Pluvialis squatarola 灰斑鸻 Huī bān héng||3|
|GREY-TAILED TATTLER Tringa brevipes 灰尾漂鹬 Huī wěi piāo yù||2|
|WATER PIPIT Anthus spinoletta blakistoni 水鹨 Shuǐ liù||1|
|ROSY PIPIT Anthus roseatus 粉红胸鹨 Fěnhóng xiōng liù||1|
|WOOD SANDPIPER Tringa glareola 林鹬 Lín yù||1|
|COMMON GREENSHANK Tringa nebularia 青脚鹬 Qīng jiǎo yù||1|
|LITTLE RINGED PLOVER Charadrius dubius 金眶鸻 Jīn kuàng héng||1|
|NORTHERN SHOVELER Anas clypeata 琵嘴鸭 Pí zuǐ yā||1|
|TAIGA FLYCATCHER Ficedula albicilla 红喉姬鹟 Hóng hóu jī wēng||1|
Detailed species accounts are below, giving more detail about the volume, frequency and date ranges as well as examples of the calls recorded. There is also an explanation about three particularly troublesome groups – the ‘tseep’ thrushes, ‘tick’ buntings and Muscicapa/Fidecula flycatchers, most of which have not yet been identified to species level.
Over time, we plan to use observational weather data to examine the correlation between volume and weather conditions, including temperature, wind strength and direction, cloud cover, moon phase and illumination.
The autumn 2021 pilot project has provided a snapshot of the scale and diversity of migratory birds flying over Beijing as its residents sleep. Given that it is very likely that migration happens on a broad front over the city, not all species call, and that among those species that do call at night, there will be variation in the rate of calls, the number of bird calls recorded by this project is likely to represent a small fraction of the total volume of birds migrating over the city.
Given Beijing’s location on the East Asian-Australasian Flyway, and that the majority of the more than 500 species recorded in the capital are migratory, it is clear that the main responsibility of China’s capital city in the flyway is to facilitate safe passage for migratory birds over the rather hostile urban environment. It is interesting to note that the top three species by volume were Olive-backed Pipit (a bird of woodland), Black-crowned Night Heron (a wetland bird) and Eurasian Skylark (a grassland bird). This reinforces the view that, if Beijing is to fulfil that role to provide safe passage for migratory birds, it should consider a balanced approach to habitat protection and restoration to include woodland, wetlands and scrub/grassland. This will be a key message in the briefing for government officials and media, scheduled to take place at AIIB headquarters this summer.
Plans for 2022
In 2022, we are expanding the project to cover more locations in order to gain a better sense of the scale of migration over Beijing and to compare locations with different levels of light pollution. Given the number of birds, especially shorebirds and flycatchers, already passing through at the beginning of the recording period in autumn 2021, we plan to start the autumn recording earlier, from mid-July, and run through to mid-November. For the spring recording we plan to start in mid-March and run through to mid-June.
For the autumn 2021 pilot project each audio file was processed manually. However, with multiple locations in 2022, the intensity of labour required to do this will be prohibitive. Through a collaboration with Cornell Lab of Ornithology we hope to be able to train AI software with the calls of at least the most common East Asian nocturnal flight calls to help us to process audio files more efficiently.
This project would not have been possible without the wonderful team at AIIB, including Sir Danny Alexander, Alberto Ninio, Li Zeyu and Tian Hua. The team at Peking University, led by Assistant Professor Hua Fangyuan, and including 张棽(Zhāng Shēn), 任晓彤 (Rèn Xiǎotóng), 刘双祺 (Liú Shuāngqí) and 杨晓彤 (Yáng Xiǎotóng), has been a joy to work with and I look forward to continuing cooperation in 2022 and beyond. Andrew Farnsworth at Cornell Lab has provided valuable advice and encouragement and we look forward to working together with him and his team, especially Benjamin Van Doren, as this project expands. A number of people have helped with the identifications, including Jonas Buddemeier, Geoff Carey, David Darrell-Lambert, James Eaton, Paul Holt, James Lidster, Magnus Robb and Seán Ronayne, to whom we owe a debt of gratitude.
Detailed Species Accounts (by volume).
OLIVE-BACKED PIPIT Anthus hodgsoni 树鹨 Shù liù
Status in Beijing: Common passage migrant in spring (April and May, peaking in early May) and autumn (late August to October, peaking in late September and early October). Uncommon in winter. Possibly breeds on occasion in the mountains.
Total Calls: 24,811
Date range: 28 August 2021 to 1 November (peak 1,906 on 10 September)
Example call: Olive-backed Pipit, 6 September 2021 @ 2239 hrs
BLACK-CROWNED NIGHT HERON Nycticorax nycticorax 夜鹭 Yè lù
Status in Beijing: Common breeder and passage migrant, and a few winter. Numbers peak between April and September.
Total calls: 5,358 (note that a proportion of these will almost certainly be local breeders or locally fledged birds)
Date range: 25 August to 1 November (peak 791 on 30 September)
Example call: Black-crowned Night Heron, 4 September 2021 at 0043 hrs
EURASIAN SKYLARK Alauda arvensis 云雀 Yúnquè
Status in Beijing: Rare breeder, very common passage migrant, peaking in early April and early October, and winter visitor.
Total calls: 2,606
Date range: 22 September to 30 October (peak: 1,388 on 15 October)
Example call: Eurasian Skylark, 21 September @ 2145 hrs
COMMON ROSEFINCH Carpodacus erythrinus 普通朱雀 Pǔtōng zhūquè
Status in Beijing: Common passage migrant in spring (late April and May) and autumn (late August to November). Rare in March, June, July and December.
Total calls: 2,124
Date range: 26 August to 26 October (peak: 790 on 14 September)
Example call: Common Rosefinch, 3 September @ 0245 hrs (typical call followed by a more unusual song element)
YELLOW-BELLIED TIT Periparus venustulus 黄腹山雀 Huáng fù shānquè
Status in Beijing: Common passage migrant (peaking in April and October), fairly common but local breeder, primarily in the mountains, and increasingly recorded in winter since the first record in that season on 28 January 1997 at Baiwangshan (Jesper Hornskov). Increasing.
Total calls: 549
Date range: 19 September to 27 October (peak: 121 on 19 September)
Example call: Yellow-bellied Tit, 2 October @ 0457 hrs
BRAMBLING Fringilla montifringilla 燕雀 Yànquè
Status in Beijing: Common passage migrant and winter visitor to urban and rural Beijing (late September to May).
Total calls: 329
Date range: 2 October to 2 November (peak: 78 on 30 October)
Example call: Brambling, 26 October @ 0221 (two typical calls plus contact calls)
EASTERN YELLOW WAGTAIL Motacilla tschutschensis 黄鹡鸰 Huáng jí líng
Status in Beijing: Common passage migrant in spring (April and May, peaking in early May) and autumn (mid-August to early October, peaking in early September). Races recorded in Beijing are tschutschensis/plexa, macronyx and taivana.
Total calls: 311
Date range: 25 August to 21 September (peak: 57 on 4 September)
Example call: Eastern Yellow Wagtail, 1 September @ 2247 hrs
RICHARD’S PIPIT Anthus richardi 理氏鹨 Lǐ shì liù
Status in Beijing: A common passage migrant in spring (mostly late April and May) and autumn (August to early October), and a scarce and local breeder in grassland habitats.
Total calls: 266
Date range: 26 August to 15 October (peak: 105 on 10 September)
Example call: Richard’s Pipit, 10 September @ 0134 hrs
RED-RUMPED SWALLOW Cecropis daurica 金腰燕 Jīn yāo yàn
Status in Beijing: Common summer breeder and passage migrant (late March to early October).
Total calls: 252
Date range: 28 August to 27 September (peak: 178 on 27 September)
Note that all the calls of this species were recorded within 16 minutes of sunrise.
Example call: Red-rumped Swallow, 28 August @ 0454 hrs
SILVER-THROATED TIT Aegithalos glaucogularis 银喉长尾山雀 Yín hóu cháng wěi shān què
Status in Beijing: Common resident breeder and short-distance migrant in urban and rural Beijing.
Total calls: 248
Date range: 15 & 19 October only (peak: 240 on 15 October)
Note that all calls of this species were recorded within 30 minutes of sunrise.
Example call: Silver-throated Tit, 15 October @ 0537 hrs
WHITE WAGTAIL Motacilla alba 白鹡鸰 Bái jí líng
Status in Beijing: Very common summer breeder, passage migrant and scarce winter visitor. Race leucopsis breeds; ocularis is a common passage migrant and occasional winter visitor; baicalensis is a scarce but annual passage migrant; alba is a rare but annual passage migrant; lugens is a rare but annual winter visitor; and personata is a rare vagrant. Spring migration peaks in mid-April and, in autumn, in late September.
Total calls: 204
Date range: 25 August to 2 October (peak: 41 on 29 September)
Example call: White Wagtail, 2 October @ 0457 hrs
SIBERIAN ACCENTOR Prunella montanella 棕眉山岩鹨 Zōng méishān shí liù
Status in Beijing: Fairly common winter visitor and passage migrant (October to April). Rare in September and May.
Total calls: 125
Date range: 5 October to 1 November (peak: 54 on 27 October)
Example call: Siberian Accentor, 26 October @ 0521 hrs
GREY HERON Ardea cinerea 苍鹭 Cāng lù
Status in Beijing: Common breeder, passage migrant and winter visitor in lower numbers. Breeds alongside Purple Heron in reedbeds at Yeyahu and on cliffs at Shidu, Fangshan District.
Total calls: 108
Date range: 26 August to 31 October (peak: 24 on 9 October)
Example call: Grey Heron, 28 August @ 2153 hrs
ORIENTAL MAGPIE Pica serica 喜鹊 Xǐquè
Status in Beijing: Abundant resident in urban and rural areas.
Total calls: 104
Date range: 21 September to 29 October (peak: 62 on 29 October)
Note that all the calls of this species came within 15 minutes of dawn, thus most likely local birds leaving roosts.
Example call: Oriental Magpie, 28 August 2021
SIBERIAN RUBYTHROAT Luscinia calliope 红喉歌鸲 Hóng hóu gē qú
Status in Beijing: Fairly common passage migrant in spring (May) and autumn (mid-August to early October, peaking in mid-September).
***This call has been identified as Siberian Rubythroat as it is very similar to one of the diurnal calls made by this species (Paul Holt and Jonas Buddemeier). However, the date range of the nocturnal recordings is not consistent with sight records in Beijing (observational data show that the migration window is mid-August to early October, peaking in mid-September), so there is an inconsistency.***
Total calls: 84
Date range: 25 August to 17 September (peak: 48 on 27 August)
Example call: ?Siberian Rubythroat, 27 August @ 0156 hrs
STRIATED HERON Butorides striata 绿鹭 Lǜ lù
Status in Beijing: Scarce breeder and passage migrant (April to September); most often seen along wooded mountain streams/rivers.
Total calls: 48
Date range: 25 August to 7 October (peak: 10 on 30 September)
Example call: Striated Heron, 4 September @ 1942 hrs
PINE BUNTING Emberiza leucocephalos 白头鹀 Báitóu wú
Fairly common winter visitor (late September to early May), often in large flocks.
Total calls: 45
Date range: 15 October to 19 October (peak: 35 on 15 October)
Pine Bunting, 11 October @ 0443 hrs
GREEN SANDPIPER Tringa ochropus 白腰草鹬 Bái yāo cǎo yù
Status in Beijing: Common passage migrant and winter visitor. Recorded in all months.