Data Zone
Cinnamon-rumped Trogon © Thipwan/Shutterstock
This annual update summarises and profiles some of the key developments in bird science and conservation during 2023. Since the last comprehensive edition of State of the World’s Birds was published in 2022, knowledge and evidence has continued to accumulate about the changing conservation status and trends of the world’s birds (STATE), the threats causing birds to decline (PRESSURE), and the conservation actions being taken to improve their status (RESPONSE).
BirdLife International is the official Red List Authority for birds, responsible for assessing and documenting the global extinction risk of all 11,000+ species for the IUCN Red List. Following transparent expert discussions on BirdLife’s Globally Threatened Bird Forums, the 2023 Red List update saw 11 species uplisted to higher threat categories due to a genuine deterioration in status, while just 4 were downlisted to lower threat categories due to an improvement in status. Many other species were reclassified for non-genuine reasons, such as better knowledge or taxonomic changes.
Among the species moved to higher threat categories were several island endemics suffering the impacts of invasive species. Two of Hawaii’s honeycreepers—Anianiau Magumma parva and Kauai Amakihi Chlorodrepanis stejnegeri—moved from Vulnerable to Endangered following estimated population declines of more than 60% during 2008–2018, largely as a result of avian malaria carried by introduced mosquitos. Elsewhere, Juan Fernandez Tit-tyrant Anairetes fernandezianus, endemic to Robinson Crusoe Island off the coast of Chile, was uplisted from Near Threatened to Endangered after invasive plants and introduced predators drove rapid population declines.
Forest loss also continues to drive population declines worldwide. Citron-throated Toucan Ramphastos citreolaemus was moved from Least Concern to Near Threatened due to the ongoing effects of forest loss in South America, while in South-East Asia, Cinnamon-rumped Trogon Harpactes orrhophaeus was uplisted from Near Threatened to Vulnerable due to loss and fragmentation of its lowland forest habitat.
However, downlisted species provide reasons for hope, showing the positive impacts of conservation actions. Thanks to local community efforts to conserve habitats and prevent persecution, three Asian stork species—Greater Adjutant Leptoptilos dubius, Lesser Adjutant Leptoptilos javanicus and Painted Stork Mycteria leucocephala—were moved to lower threat categories. In Hawaii, successful translocation of Millerbird Acrocephalus familiaris from Nihoa to Laysan during 2011–2012 has resulted in a self-sustaining population, warranting downlisting of the species from Critically Endangered to Endangered.
Number of species in each IUCN Red List category (numbers in red indicate the net change since the previous year's assessment).
Forests are home to nearly two-thirds of all bird species, including more than 70% of globally threatened species. However, forests in Key Biodiversity Areas (KBAs, most of which have been identified for birds) across the world are being lost, fragmented and degraded. The Forest Landscape Integrity Index (FLII) describes the ecological integrity of the world’s forests using data on forest extent, threats and changes in connectivity. Analysis of the FLII in KBAs that contain forest and have been identified for forest species reveals that only 44% (1.7 million km2) of the forest extent within these KBAs is classified as high integrity. KBAs in South America, Africa and Asia have the greatest amount of high integrity forest, while KBAs in Europe, Central America and the Caribbean have the highest proportion of low integrity forest. Loss of forest integrity at these sites reduces capacity to conserve the species for which they have been identified as internationally significant. Areas of high integrity forest in KBAs that currently lack protection are among the highest priorities for assessing required conservation actions, including restoration to increase connectivity and reduce fragmentation.
Ruff Calidris pugnax is a Species of European Conservation Concern owing to a significant population decline and range contraction. Photo © Sandhanakrishnan/Shutterstock
BirdLife’s fourth assessment of the population status of all of Europe’s 546 bird species reveals that 38% are of conservation concern, including 14% of global concern. Many species have been in trouble for decades and are still declining or depleted. Among them are numerous farmland and steppe birds, ducks, waders, raptors, seabirds and long-distance migrants. To this list, the latest assessment adds a range of species that breed in northern Europe and montane regions. Conservation action under policy instruments like the EU Birds Directive has helped some species to recover, including various raptors and large waterbirds. But much more action is needed to halt and reverse losses, highlighting the urgency of adopting and implementing comprehensive legislation for nature restoration.
Analysis of data from BirdLife’s latest species assessments for the IUCN Red List shows that the threats affecting the greatest number of the world’s threatened bird species are (in descending order) agriculture (73% of species), logging (51%), invasive alien species (42%), hunting and trapping (39%), and climate change (37%). These same threats also emerge highly from monitoring of Important Bird & Biodiversity Areas (IBAs) by the BirdLife Partnership.
The relative importance of different threats to globally threatened bird species based on the proportion of species affected. Threats that occurred in the past and are thought to be unlikely to return are not included. Many species are affected by more than one threat.
The global outbreak of high pathogenicity avian influenza that started in 2021 has impacted more than 400 bird species, including numerous seabirds, waterbirds and raptors. Photo © Matauw/Shutterstock
In 2021 a new H5N1 variant of clade 2.3.4.4b Highly Pathogenic Avian Influenza (HPAI) managed to survive the summer in Europe and replace the circulating H5N8 variant. Highly deadly, effective at circulating within wild bird populations, and able to infect a large number of species, the virus caused significant mortality of birds throughout the continent. From Europe, migratory birds carried the virus to Africa, Asia, the Americas and, most recently, the Antarctic region. Numerous cases of mass mortality among waterbirds, seabirds and birds of prey have been reported, in some cases resulting in significant population declines. While there is no quick solution, the BirdLife Partnership is working together to monitor the situation and minimise spread of the virus where possible.
Rapidly increasing global plastic production alongside ineffective waste management has resulted in millions of tonnes of plastics in our oceans. These plastics are a threat to marine life, including seabirds, through entanglement and ingestion. Seabird tracking data combined with estimates of marine plastic density can reveal areas in which seabirds are at high risk of exposure to plastic pollution, and populations that regularly utilise these high-risk areas. Data from 77 tracked petrel species reveal hotspots of exposure risk in the Mediterranean and Black seas, and the northeast Pacific, northwest Pacific, South Atlantic and southwest Indian oceans. Worryingly, exposure risk is disproportionately high for globally threatened species.
Hotspots of plastic exposure risk for tracked petrels
Birds show that with effective conservation action, species can be saved and nature can recover. One of the most important actions needed to conserve birds and other biodiversity is to effectively protect, safeguard and manage the most critical sites for their conservation—Key Biodiversity Areas (KBAs, many of which have been identified for birds). Globally, the average area of each KBA covered by protected areas and ‘other effective area-based conservation measures’ (OECMs) has steadily increased from 11% in 1980 to more than 43% in 2023.
While state-governed protected areas play a critical role in site-based conservation, it is also important to consider the contribution of other governance and management systems. Indigenous Peoples’ Lands cover at least 28% of the land area of Key Biodiversity Areas (KBAs), of which around half currently falls outside of the protected area network. Research suggests that the rate of tree cover loss in KBAs that fall outside of protected areas but within mapped Indigenous Peoples’ Lands is lower than in KBAs that fall outside of both protected areas and mapped Indigenous Peoples’ Lands. This suggests that Indigenous Peoples’ Lands may contribute to conservation of these sites. However, there is significant variation between countries, so more research is needed to understand the factors influencing the ability of Indigenous Peoples’ Lands to have positive biodiversity outcomes.
Rate of tree cover loss in forest KBAs inside and outside of mapped IPL and protected areas
Whimbrel Numenius phaeopus migrates 15,000 km annually between North and South America. Conserving critical sites for Whimbrel and other bird species along their migratory routes requires coordinated action. Photo © Bjorn Olesen
In September 2023, BirdLife International, the National Audubon Society and the Development Bank of Latin America and the Caribbean (CAF) launched the Americas Flyway Initiative (AFI)—an innovative approach to tackling the biodiversity and climate crises in the Western hemisphere. The initiative will identify more than 30 critical landscapes and seascapes for migratory and endemic threatened resident birds along the Americas flyways for urgent conservation, restoration, and management by local partners, communities, and Indigenous Peoples. Supported by innovative funding mechanisms, projects in these areas will focus on integrating and scaling up nature-based solutions and incorporating bird-friendly design features into urban and rural infrastructure projects to deliver long-lasting benefits to local communities and biodiversity. AFI represents an unprecedented investment in sustainable development in the Americas.
BirdLife's work on State of the World's Birds is generously funded by the Aage V. Jensen Charity Foundation.