World Migratory Bird Day will be celebrated on 9 May 2026, an event promoted by the United Nations through the Convention on the Conservation of Migratory Species of Wild Animals. At CESAM, some of these birds are the focus of research by a team of scientists, namely migratory wading birds.
This group of birds includes the species holding records for the longest non-stop migratory flights on the planet. Along the East Atlantic Flyway, which includes Portugal, the record holder is the whimbrel (Numenius phaeopus), capable of flying more than 5,500 km over five days and five nights without stopping to rest, travelling at an average speed of 54 km/h between Iceland, where it breeds, and West Africa, where it spends most of the non-breeding season. A recent study also revealed that juveniles of this species demonstrate these remarkable athletic abilities from a very early age: at just two months old, they undertake similar flights across the Atlantic Ocean, although shorter and at lower speeds of around 35 km/h.
To celebrate these and other extraordinary feats, the theme of World Migratory Bird Day 2026 is “Every Bird Counts – every observation matters!”. This slogan aims to encourage citizen science through public participation and contribution towards a better understanding of these species. Researchers make use of records collected by members of the public to study these birds, particularly observations of individuals marked with unique combinations of coloured leg rings, which can be identified by any properly equipped observer. By recording the species, the colour-ring combinations placed by researchers on the birds’ long legs, as well as the location, date, and time of observation, and later reporting this information by email, anyone interested can contribute. Such information has already helped researchers identify the most important sites for the migratory connectivity of the black-tailed godwit (Limosa limosa) along its migratory route, and determine whether juvenile Eurasian oystercatchers (Haematopus ostralegus) follow the migratory behaviour of their father or mother.
Despite their fascinating migratory behaviour, migratory waders are on the frontline of global change. They must cope with polar amplification — the accelerated warming occurring in polar regions, particularly in the Arctic where many of these species breed. During the non-breeding season, when they concentrate in coastal areas such as estuaries and beaches, they are increasingly affected by the uncontrolled construction of infrastructure and growing disturbance in these habitats, leading to serious alterations to their environment. Unfortunately, many of these species are currently experiencing severe population declines, some by as much as 30% in recent years.
It is therefore no surprise that two of the seven ambassador species selected for this year’s celebration are migratory waders: the Eurasian oystercatcher (Haematopus ostralegus), a partial migrant already mentioned, and the spoon-billed sandpiper (Calidris pygmaea), a critically endangered species. To support knowledge and conservation of these species on a global scale, CESAM researchers created the Global Wader platform, a forum for sharing information on waders tracked using electronic devices such as GPS tags. This type of monitoring is carried out not only by researchers, but also by NGO members and volunteer bird-ringing groups. Through this platform, global tracking data on waders are made available to foster collaborations and support species conservation, as demonstrated by its contribution to the designation of the Bijagós Archipelago in Guinea-Bissau as a UNESCO World Heritage Site. In this way, CESAM also contributes to another of the key goals of World Migratory Bird Day: a global effort across all migratory flyways.
News article by José Alves, CESAM/DBIO researcher.
