Over 220,000 Sparrows Estimated in Hong Kong Revealing a Stabilizing Population
HKBWS Collaborates with Citizen Science Platform Aiming to Establish Urban Bird Database
The 9th Hong Kong Sparrow Census today estimated that the number of Eurasian Tree Sparrows (referred to as “sparrows” below) is approximately 222,000 in urban areas of Hong Kong, with a slight decrease of 8.6% compared to last year. This marks the seventh consecutive year that the sparrow population has remained at around 200,000, indicating a stabilization in sparrow numbers. HKBWS emphasizes the need for ongoing monitoring and data collection to better understand population trends and calls for the public to submit bird data, aiming to establish urban bird database in long-term for more in-depth research.
Sparrow Numbers Stabilize with Tuen Mun Leads in Population
The census was conducted from May 5 to 18, 2024, covering six land uses across 18 districts in Hong Kong (residential, commercial, industrial, recreational, agricultural and rural areas). Over 250 volunteer surveyors counted sparrows along 86 pre-defined routes, approximately one kilometer each, in the early morning. This allowed for calculating the number of sparrows per square kilometer and then extrapolated to estimate the total population of sparrows in Hong Kong.
According to the results, there are approximately 222,000 sparrows in urban areas, a decrease of about 20,000 from last year, with an 8.6% annual decline. Among the 18 districts, Tuen Mun is the area with the highest density of sparrows, where each route averages around 90 sparrows, followed by Sha Tin and Sham Shui Po. If categorized by land use, the areas with the most sparrow clusters are residential areas, followed by rural areas and recreational zones. It is estimated that there are about 66,000 sparrows in residential areas, accounting for nearly 30% of the total in Hong Kong.
Sparrows utilize urban structures for nesting. Among the 79 nests recorded this year, 33% were in drainage or vents, 15% on vegetation, followed by outer wall structures (12%), air conditioning (11%), and eaves (10%). Arthur Yu, the Assistant Education Manager of HKBWS, explained that the more hidden locations, such as vents and air conditioning, provide protection for chicks. It makes these sites preferred nesting spots. Thus, these various urban structures are essential habitats for sparrows which offer both nesting and roosting sites.
Since 2018, the population of sparrows has maintained a level between 200,000 and 250,000 for seven consecutive years, showing that the population is gradually stabilizing. However, when compared to the 300,000 sparrows estimated in 2016, the number of 2024 shows a nearly 30% decline. The reasons for this decrease remain unclear due to the limitations of current census research methods, but urban redevelopment and the construction of new skyscrapers may reduce suitable habitats for sparrows. In the long term, continuous monitoring of sparrow populations is necessary to understand the trends.
Urge for Promoting Urban Biodiversity and Build Bird-Friendly Cities
This year marks the fifth year that four additional common urban bird species have been included in the census: the Spotted Dove, Oriental Magpie-robin, Red-whiskered Bulbul, and Blue Magpie. The populations of the Oriental Magpie-Robin and Red-whiskered Bulbul saw increases, estimated at 20,000 and 65,000 respectively, while the number of Spotted Dove and Blue Magpie slightly decreased, estimated at 51,000 and 3,400 respectively.
Overall, the populations of these four common urban birds are stabilizing. Among the six land uses, the Spotted Dove, Oriental Magpie-robin, and Blue Magpie have the highest densities in recreational areas. It indicates that urban green spaces are vital habitats for urban birds, with fruits and seeds from trees being their key food sources.
Arthur Yu, the Assistant Education Manager of HKBWS, recommends that the government promote urban biodiversity by increasing urban greening, planting native plants and trees, and providing more foraging and nesting spaces for wild birds. Additionally, efforts should focus on mitigating urban impacts on biodiversity to make cities friendlier for birds. Arthur Yu noted, "In recent years, the designs of new buildings differ from tenement buildings that feature uneven facades, verandas, and ventilation ducts, which lack spaces for birds to perch or nest. Besides, more skyscrapers and redevelopment projects will diminish the suitable nesting areas for birds and potentially affect sparrow populations." Furthermore, many new buildings utilize glass facades designs, which not only hinder urban birds from roosting or nesting but also increase the risk of bird-window collisions, imposing a threat to urban biodiversity in the long run.
Encouraging Public Submitting Bird Record through Citizen Science App
Since 2016, HKBWS has conducted the Sparrow Census annually in spring. The Census not just to provide essential baseline data for local bird studies, but also encouraged public participation in bird surveys through citizen science. This year, over 250 volunteer surveyors participated in the Census, achieving a post-pandemic record for participation.
To further promote citizen science, HKBWS has partnered with the citizen science platform eBird to facilitate bird record submissions. By downloading the "eBird" mobile app, the public can record birds anytime, anywhere, and upload their data instantly. These data will provide essential baseline data for local urban bird research and aid in long-term planning for urban biodiversity.
In fact, the adaptable sparrow serves as a good environmental indicator. Its population changes can reflect the health of urban ecological environments to monitor and understand the changes in urban environments. A significant drop in sparrow numbers in any area may signal an important environmental alert. HKBWS cordially invites the public to actively submit bird records to help establish an urban bird database and urges citizens to "count more, know more" for continuous monitoring to let common birds remain common.
eBird is the world's largest bird record database and citizen science platform established in 2002 by the Cornell Lab of Ornithology and the National Audubon Society. Its aim is to encourage bird watchers to share bird records and gather data to share with scientists, educators, and conservationists worldwide. Each year, eBird receives over 100 million bird sightings from users around the globe.
