The meteoric rise of the chiffchaff as more than half of bird species populations increase over 20 years

The latest official statistics on 66 Scottish terrestrial breeding bird species released by nature Scot shows increases for 36 species between 1994 and 2023, with 23 showing decline and seven remaining stable.

However, the endangered capercaillie has seen another 17 per cent decline in its already-declining numbers, linked to death from collisions with fences and potentially a negative effect of rising temperatures from climate change.

The population of the woodland chiffchaff has risen by 1,428 per cent, while the number of greater spotted woodpeckers is almost seven times higher and blackcap numbers have risen 593 per cent.

the population of chaffinches, one of Scotland’s most common birds, has dropped by 13 per cent, driven by the suspected presence of bird parasite trichomonas gallinae, which is linked to unhygienic bird feeding areas.

Upland birds have shown the largest declines at around 20 per cent. Long-term changes in upland bird populations have been contributed to by several factors, including climate change, forest expansion, and changes in site-based management practices such as grazing and predator control.

Curlew breeding numbers have declined over 60 per cent, and changes to land management, climate and food availability are all having an impact.

Simon Foster, NatureScot trends and indicators analyst, said: “Since many bird populations are widespread and abundant, can respond quickly to environmental change, and are well surveyed in the UK through volunteer-based and professional surveys, they are useful biodiversity indicators. This report clearly shows that the emerging long-term differences in Scotland’s terrestrial breeding bird populations are dependent on a species’ ability to adapt to climate and habitat changes.

“Not only do we have our part to play in ensuring Scotland’s habitats are supported to function at the best of their potential for nature, but we can also make space for nature in our gardens by keeping feeding areas clean to help reduce the chance of diseases being passed within bird populations. Ensuring that sufficient food for only one to two days at a time is left in feeders, and that bird stations are regularly cleaned, is a great start.”

Swifts are experiencing a substantial long-term decline, which may be related to the reduced availability of suitable nesting sites on buildings, though a reduction in availability of flying insects may also play a role. Swifts are long-distance migrants and there may also be factors that influence their survival outside the breeding season during migration or on their wintering grounds. Action to create nesting sites is underway in some of our cities.

The report added that between 1994 and 2023, there has been a long-term increase of seven per cent among the species trends that contribute to the farmland bird indicator. This increase was largely due to positive population trends in areas dominated by pastoral farmland, where the index increased by 22 per cent.

Farmland waders such as oystercatcher and lapwing have seen the largest declines, and these have been linked to changes in farming practices. However, there are considerable efforts to reverse the trends for breeding waders across Scotland through projects such as Working for Waders.

The study added: “Trends differ between species and may be due to factors within the breeding areas in Scotland or, for migratory birds such as whitethroat trends can be influenced by conditions on migration routes or wintering areas. Climate change is clearly affecting some bird populations with evidence of birds shifting northwards eg willow warbler.”