OWhile hot summer days may seem like good news for British wildlife – and indeed they may be for some heat-loving insects, such as dragonflies – for many species of birds, mammals and insects, current drought conditions are far from ideal.
The British Trust for Ornithology (BTO) has warned that some of our most beloved garden birds are already in trouble, as they try to raise their second brood of young. Robins, robins and song thrushes need regular summer rains, as this creates wet conditions that bring earthworms and other soil invertebrates to the surface of garden lawns.
Droughts mean the worms stay in the wetter earth, which means the birds can’t catch enough of them to feed themselves or their chicks. This can lead to desperate measures: during the very dry spring and summer of 2011, hungry blackbirds even resorted to cannibalism, feeding on their own offspring. The RSPB charity advises extinguishing mealworms to provide an alternative food source for birds.
Ground-feeding mammals such as badgers and hedgehogs also suffer from the unusually dry weather; not only because they don’t have enough food, but also because of overheating and dehydration. And while warm, sunny days may be better than humid, rainy days for adult butterflies as they fly from plant to plant to lay their eggs, that’s bad news for caterpillars, which need plenty of foliage on their host plants if they are to nurture and grow. A recent study showed that in years following prolonged summer droughts, when plants die early from heat, butterfly populations tend to decline.
Other insects also struggle to cope with hot weather, but for different reasons. Professor Dave Goulson of the University of Sussex points out that because bumblebees have hairy coats – an adaptation to flight and foraging in cool conditions – they are unable to feed in very high temperatures.
As temperatures reach record highs, young swifts, swallows and swifts are at risk of fatal overheating. Recently in London, young swifts that had been forced out of their nests before they were fully adults were seen falling from the sky. House swallows are also unable to find enough mud to build or repair their nests.
Prolonged dry weather increases the risk of forest fires, which spread very quickly, especially in moorland and moorland. As early as April this year, 17 hectares (42 acres) of valuable wildlife habitat were destroyed at Canford Heath in Dorset, threatening the breeding success of rare species such as Dartford warblers, sand lizards and grass snakes smooth. And in July, a fire raged through the coastal scrub and reedbeds of Wild Ken Hill in Norfolk, home to the BBC’s Springwatch program.
Elsewhere in East Anglia, wetlands such as the Ouse Washes are starting to dry out. If enough rain doesn’t fall soon, the BTO fears the young of some wading bird species, including the avocet, may not be able to find food. Other waders that nest in bogs may also struggle if the peat dries out, as this would mean that leatherjacket larvae – the food of Dunlin and Golden Plover – are unable to survive.
For all of these species, a single bad summer, with resulting low reproductive success, may not be a total disaster. But if summer droughts become the norm, due to the cumulative effects of the climate crisis, then breeding populations can decline very quickly.
This is not the first time that a summer drought has caused problems for wildlife. Anyone who lived through the summer of 1976 will remember the “plague of ladybugs” that appeared from July onwards, forcing holidaymakers to flee beaches covered in thousands of these black and red beetles. Ladybugs first took advantage of the dry weather, which produced an early glut of their favorite food, aphids. But as the drought continued and plants began to wilt and die, the aphid population crashed and the ladybugs swarmed in search of alternative food sources.
In the decades that followed, warming temperatures allowed several species of exotic birds to expand their ranges northward. The BTO suggests that the current drought in southern Europe could speed up this process, allowing black-winged stilts and bee-eaters to breed more frequently in the UK. While this may be good news for bird watchers, it is also a clear sign that climate change is causing problems for these Mediterranean species, and a timely warning to us.
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