World Migratory Bird Day
Saturday 8 May is World Migratory Bird Day 2021. For many species, what seems like a perilous journey at the best of times has become a serious threat to their futures.
Migratory birds, and long-distance migrants in particular, are among the most threatened species. Given the perils of migration, that may seem obvious, but for milennia, some of the apparently most delicate birds have managed to cover thousands of miles twice a year. The globe’s higher latitudes enjoy a superabundance of insect prey, and continuous daylight during which to exploit it, but for a few weeks only. They must spend most of the year somewhere else.
The northern wheatear has one of the largest ranges of any songbird in the world, with breeding grounds in the eastern Canadian Arctic, Greenland, Eurasia and into Alaska. They all winter in Africa, following the longest routes undertaken by any small land bird. Birds fitted with tiny data loggers in Alaska have been found to migrate more than 18,000 miles a year using routes they inherited from the Pleistocene, before their breeding range expanded to include the Western Hemisphere. A few weeks from now, young wheatears who have never seen darkness will carry the light of the Arctic across the burning sands of the Sahara to seek sanctuary in the Sahel.
Climate change around 10,000 years ago may have created new opportunities that some birds were able to exploit rapidly by adapting their migration patterns, but erratic and even faster changes in Africa are thought to be the main threat to many migrants today.
UK Species that winter in Africa’s humid zone (such as whinchats, nightingales, tree pipits and spotted flycatchers) show the most dramatic declines; collectively their numbers have dropped by over 70% since the late 1980s. This contrasts with species wintering in the arid Sahelian areas of Africa (including sand martins, whitethroats and sedge warblers), which have fluctuated considerably since 1970 but show a less than 20% decline overall. The largest declines in this group were probably in the late 1960s with whitethroats and sand martins suffering infamous population crashes from which they have since partly recovered.
Species wintering farthest south, such as cuckoos, swifts and swallows, also show a substantial decline since the early 1980s, whereas species that winter on this side of the Sahara have substantially increased since the mid-1980s. This group includes blackcaps, meadow pipits, chiffchaffs and stonechats.
In 2016 I accompanied many of Europe’s migrants home, as best I could, as I followed the arrival of Spring through Europe, and told the story in my book The Long Spring. To celebrate World Migratory Bird Day, you can buy it from this website during May for £3 off!