(Translated from Swedish) The number of bird species included in the Red List has risen significantly: compared to 2015, it has increased by 21%. Of all the bird species reviewed, 45% are included in the Red List. This raises the question: why is such a large number of species included in the Red List? Many forest-dwelling bird species have been included in the Red List, even though it is known that population trends have generally been positive.

Following a press release published by the Swedish University of Agricultural Sciences, several media outlets reported that the number of individuals of 30% (and in some cases even one-third) of bird species is decreasing so rapidly that they are being included in the Red List.

The large increase in the number of bird species included in the Red List surprised me, because recently there have generally been positive trends regarding birds, as established in the Svensk Fågeltaxering report. Only 15% of the 204 bird species that birdwatchers have monitored over the last 10 years showed a declining trend, while 19% of species saw an increase in numbers, which is confirmed by statistical data.

Why do Red List data show that 30% of bird species are rapidly declining in number, while the Svensk Fågeltaxering report indicates that a rapid decline in individual numbers is observed in 15% of species?

The first explanation: the press release from the Swedish University of Agricultural Sciences was incorrect (corrections were made on its website after 2 weeks, indicating 26%). But only 23% of the bird species in Sweden are included in the Red List under Category A due to the rapid decline in their numbers. 5 more bird species are included in the Red List under Category C because their populations are small and declining trends are expected. These calculations include ongoing declines that are not considered significant. This mostly applies to those bird species for which no statistically supported decline in numbers has been observed. Sometimes these data contradict data obtained from bird monitoring projects. For example, according to the Species Information Centre (Artfakta), the number of buzzards has decreased by 5% over 21 years, but according to the Svensk Fågeltaxering project report, the performance of this species in 2019 was better than ever before. Including the species in Category C, a total of 25% of regularly nesting bird species are included in the Red List due to a decline in their numbers.

Another explanation for the large discrepancy in the data: different time periods are being compared. In the case of long-lived birds, the decline in numbers is assessed by looking at a period longer than 10 years. Regarding forest birds, the trends over the last 20-year period are even more optimistic. According to a study conducted by the Swedish University of Agricultural Sciences and Lund University, in cases where there was sufficient evidence for assessment, 33 out of 58 forest bird species showed a significant population increase between 1998 and 2015. Only 6 forest bird species have seen a significant decline in population. However, these trends have not been as positive for bird species living in other types of natural landscapes.

The data for species that have declined rapidly according to the Species Information Centre (Category A) also differ from the information included in the Svensk Fågeltaxering report. For example, according to the Species Information Centre, the northern goshawk population has decreased by 22% over 18 years, but data from the Svensk Fågeltaxering bird monitoring report show that their population grew between 2001 and 2019. According to the Svensk Fågeltaxering project, the hazel grouse population was at a record high in 2019, but according to the Species Information Centre, its population has decreased by 25% over the last 12 years. Most likely, these differences can be explained by which years were chosen as the starting and ending reference points, and the compilers of the Species Information Centre seem not to have taken the 2019 data into account.

Returning to the question: why are so many bird species included in the Red List? It is clear that there are long-term negative trends and there is cause for concern regarding certain species groups and types of natural landscapes. This applies, for example, to ducks and migratory birds, as well as certain farmland and forest bird species. However, a large proportion of species are included in the Red List for reasons that we should not be particularly worried about.

Many bird species are included in the Red List because they are rare. 47 species were included because their population is very small. That does not mean these species' populations are declining! In most ecosystems and species groups, most of these bird species are rare – this is nothing unusual. We are generally well-acquainted with even rare bird species because many people observe birds. Species with fewer than 2,000 individuals are automatically included in the Red List. If a species has fewer than 250 individuals, it is considered critically endangered. The charm of birdwatching lies in the fact that many bird species are rare. But, for example, we often do not even have an inkling about the existence of insect species with fewer than 250 individuals.

Another significant explanation for the high proportion of birds included in the Red List is the fact that bird numbers tend to be variable, and we know how they tend to fluctuate. This most likely depends on weather conditions, the availability of rodents and berries, or interspecies competition, rather than on changes in the habitat. If we look again at the hazel grouse included in the Red List, its number of individuals has both decreased and increased several times over the period examined. In 2016, the number of hazel grouse decreased significantly; in 2019, it increased.

A similar picture can be seen for many other bird species. Every year, the populations of a large portion of bird species increase, just as the populations of a large portion of bird species decrease. Which bird species' population decreases or increases depends on which year's data we look at. There are actually more species whose populations are increasing than those whose populations are decreasing; many bird species will be included in the Red List because their population declines by at least 15%. Regarding forest bird species, the overall picture compared to the year 2000 has improved significantly. The number of bird species included in the Red List alone does not provide a complete picture of the general trends.

Data from the Svensk Fågeltaxering annual report for 2019