Early Springs Alter Breeding Seasons

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Early springs alter breeding seasons
15th April 2019

By Karen Pickwick

Climate change has advanced the breeding season of many wildlife species in the UK – but just how much varies markedly across the country, according to a major new study.

The first in-depth analysis into the seasonal timing of certain bird and insect behaviours has confirmed that spring is indeed getting earlier each year – but that exactly how much earlier these events now start depends on where in the UK and in which habitat they occur.

The authors of the report have warned these trends could have serious ramifications for ecosystems, as significant variation between groups of animals in the rates of advance means populations are becoming ‘out of sync’ with the life cycles of their prey.

The 50-year study into natural cycles of egg laying and migration has also dashed environmentalists’ hopes that shaded habitats such as forests are shielding some populations from the destabilising effects of global warming.

Lead author Dr James Bell, who heads up the Rothamsted Insect Survey, said: “There was already good evidence that spring is coming earlier each year, but what we didn’t expect to find was that it was advancing as much in forests as it is in open areas such as grassland.

“Equally, in areas where we’d expect to see much greater acceleration, such as urban parkland, the rates of advance appear to be the same.

“This all points to a complex picture emerging under climate change, which makes ecosystem responses hard to predict, and even harder for conservationists to prepare for.”

Published in the journal Global Change Biology, the study charts the seasonal habits of more than 250 UK species of birds and insects, and shows clear evidence that aphids, moths and butterflies are now on the wing, and birds are laying their eggs, much earlier than they were in the mid 20th century.

Dr James Pearce-Higgins, director of science at the BTO, said: “Birds are at the top of many food chains and are sensitive to the impacts of climate change on the availability of their insect prey. This work shows how changing spring conditions may affect the ability of birds to find food, and that those impacts are likely to vary across the country.”