Millions of common birds disappear from Finland, monitoring shows

Millions of Finland’s most common birds have disappeared in just a few years, Yle reports. Monitoring at a nature reserve in Espoo shows the scale of the decline as volunteers capture and ring birds before releasing them.

At Laajalahti nature reserve, work begins before dawn. Jari Laitasalo arrives at 4am to set up the nets, with sunrise due at around 5am. The summer-long task is divided among volunteers.

After the nets are opened, they form a 140-metre-long wall of fine thread stretching from a deciduous forest into a reed bed. The black threads are difficult to see, especially in the dim light.

The shore is home to many birds and a final resting place for others before they migrate south. The birds build up fat reserves beneath their feathers before continuing their journey.

Laajalahti is one of about 40 active inland monitoring sites where passerine birds are regularly ringed. The work is carried out in the same way and at the same locations year after year, allowing changes to be tracked.

Before each bird is released, it receives a ring bearing a serial number. If the same individual is found again, researchers can determine where and when it has previously travelled.

Common species are declining

In 2024, Finland had an estimated 5.4 million fewer birds than in 2019, a decline of about six per cent. That means the country is losing an estimated more than 2,400 birds a day.

Willow warblers, chaffinches and many warblers are among the species seen less often. These are some of the most common birds, making the change difficult to notice even though it is substantial.

Some species are doing better. They include many large birds and some smaller species that do not migrate far and are gradually moving further north as the climate warms.

International research has nevertheless found that bird song across Europe has generally become both quieter and less varied since the beginning of the 2000s.

Finnish monitoring projects show the same trend. During the past two years, fewer birds have been recorded in ringing operations than in any other period during the 40-year history of the monitoring programme.

The decline follows four consecutive summers with poor breeding results. Populations could still recover quickly if several years with strong breeding success followed, but such years are urgently needed, according to a report compiling monitoring results from previous years.

Ringing birds before release

The report was written by Petteri Lehikoinen, a researcher at the University of Helsinki. On this August morning, he sits opposite Laitasalo and weighs a warbler.

Lehikoinen coordinates the ringing project but now takes part in fieldwork less often. The two men have known each other for years, having been involved in the same birdwatching circles since childhood.

For both of them, the work at Laajalahti is voluntary. Monitoring captures are carried out almost entirely by volunteers. Bird ringing requires a permit, and only slightly more than 200 people are authorised to use the nets.

Capturing birds is not entirely without risk, but ringers consider the benefits of the work to outweigh the harm. To protect the birds, the nets may not be used in rainy weather.

The nets contain pouch-like folds where birds become caught. Ringing is done in the morning, when the birds are most active.

The work requires both a solid knowledge base and precise fingers. Laitasalo removes each bird from the tangled net by freeing its legs first, then its wings and finally its head.