The weather is all upside down

The weather of recent days has been all over the place, as if winter and spring are battling for control, each gaining the upper hand for a brief period before relinquishing their influence. Frustrating as this may be for us, it is more serious for our wildlife. Some birds have already started nesting attempts; a Collared Dove in town appears to be on eggs and our resident Blackbird has been busy collecting nesting material. Many others are in full song; Woodlarks and Yellowhammers on areas of clearfell proclaim ownership of breeding territories, while Song Thrushes, Blackbirds and Wrens provide the start of an urban dawn chorus that will grow in complexity over the coming weeks. Should winter tighten her grip then these nesting attempts will fail. Early emergence by butterflies and bumblebees, will deplete crucial energy reserves unless early season nectar can be found. It could prove to be a testing time for our wildlife.

It is not that winter is clinging on longer into the year, rather that spring is happening earlier. This, as we all know, is the result of global climate change, and is likely to be a pattern that we will see with increasing regularity over the coming years. A number of correspondents have commented upon the way in which the seasons are no longer so clearly demarcated. Instead, they increasingly blur into one another, with late season frosts, early spring-like days and winter storms arriving weeks early.

The degree to which all this might impact upon our wildlife is largely unknown. It is likely that different species will react in different ways (and with different response times) to changing weather patterns. Such are the complexities of the interactions between species that some species may slip out of synch with one another, something known as a phenological decouplement. A good example of this is a simple food chain, involving trees, the caterpillars that feed upon their leaves and the tits that feed on the caterpillars. Blue and Great Tits time their breeding attempts so that the peak demand of their chicks for food matches the peak abundance of caterpillars. However, should the trees come into leaf that much earlier, then the peak in caterpillar abundance may shift, the species in question able to react to the changing abundance of plant material. The tits would then need to bring their own breeding attempts forward to match the new peak in caterpillar abundance. While there is good evidence that tits are now breeding earlier, they may not be able to keep getting earlier or, indeed, match the speed of change in the timing of the caterpillar peak. This is something that researchers will need to watch very closely.