How many birds are there in Guangdong Province, China?

Estimating bird abundance is key to assess threats, and to prioritize conservation actions. However, few studies focus on this topic, particularly in developing countries, which may hamper conservation efficiency. We used data collected from Guangdong Province, China, between 2000 and 2020 to estimate bird abundance using MaxEnt modelling. In total, 258 bird species were included, with an average density of 1485.2 ± 489.3 ind./km² (range: 242.9–4502.2 ind./km²). The highest density occurred in the Pearl River Estuary and on the Leizhou Peninsula. For forest birds, 203 species were included with an average density of 1236.2 ± 424.5 ind./km² (143.7–2373.1 ind./km²), and highest densities were found in the Pearl River Estuary and North River regions. For the 55 species of waterbirds, the average density was 249.0 ± 351.8 ind./km² (0.3–2336.1 ind./km²). The total number of birds in Guangdong was estimated to be 2.58 × 10⁸ ind. (2.24–3.06 × 10⁸), with a total number of forest birds estimated to be 2.15 × 10⁸ ind. (1.90–2.49 × 10⁸). The most abundant forest species (>10⁷ individuals) were: Huet's Fulvetta (Alcippe hueti) with 2.84 × 10⁷ ind., (range: 2.73–2.95 × 10⁷), Light-vented Bulbul (Pycnonotus sinensis) with 1.13 × 10⁷ ind. (1.07–1.20 × 10⁷), Swinhoe's White-eye (Zosterops simplex) with 1.13 × 10⁷ ind. (1.09–1.17 × 10⁷), and Red-whiskered Bulbul (Pycnonotus jocosus) with 1.01 × 10⁷ ind. (9.66–10.47 × 10⁶). The total number of waterbirds in Guangdong was estimated to be 4.37 × 10⁷ ind. (3.38–5.75 × 10⁷). The most abundant waterbirds (>10⁶ individuals) were Black-headed Gull (Chroicocephalus ridibundus) with 6.35 × 10⁶ ind. (5.48–7.36 × 10⁶), Pied Avocet (Recurvirostra avosetta) with 5.56 × 10⁶ ind. (3.75–8.24 × 10⁶), and Little Egret (Egretta garzetta) with 5.01 × 10⁶ ind. (4.19–6.00 × 10⁶). The densities and abundances of the 41 species listed as threatened in IUCN (higher than NT) or Chinese National Protected lists (higher than Ⅱ) were evaluated, of which the population sizes of nine species were estimated for the first time in Guangdong. Moreover, all 41 species' average densities significantly declined from 2012 to 2017 in Nanling National Natural Reserve, Guangdong.