A warm autumn, short winter and March heat-wave has brought the rapid onset of spring. Migrant birds have started to arrive. The problem for the natural world is that the timing of spring is crucial to the start of the breeding cycle. For birds particularly it is vital to have chicks hatched and hungry at the moment when there are plentiful caterpillars, aphids or other diet staples available.
The evidence is that spring has shifted forward an average of 12 days since records began, and in response birds like swallows arrive about a week earlier than they did in 1970. Although the dry spring weather of the last two years may also have made a difference, it is the long-term trends that are having an effect on some of our best loved birds. Many have failed to move their breeding forward enough to coincide with the new life cycle of the insects they feed on.
For one particular species, the cuckoo, the early spring brings double jeopardy. It is known that many cuckoos target particular species of small birds, and are dependent on finding a nest and laying their egg in it at precisely the same moment as the host bird. But the earlier spring means that the cuckoos are arriving when their hosts, chiefly meadow pipits, dunnocks and reed warblers have already hatched their young. As a result in many parts of the country the cuckoo has now completely disappeared – an early victim of climate change.