Wings of the nightingale famed for its beautiful birdsong are SHRINKING due to climate change
The wings of the nightingale famed for its beautiful birdsong are shrinking in response to , a study has found. This change will make its long migrations to Africa more arduous and threaten its very survival, scientists have warned. Male nightingales, in particular, are known to sing for hours on end each night during the breeding season. However, this song may become harder to hear, with nightingale numbers having fallen dramatically over recent decades largely due to global warming. The nightingale breeds in Europe and parts of Asia, migrating to sub-Saharan Africa every winter. In the UK alone, nightingale populations have fallen by 90 per cent in the last 50 years with numbers of singing males now down to only around 5,000. Various factors have been blamed for the decline, including browsing deer that are eating them 'out of house and home' and development of the birds' former nesting grounds. Other reasons include less coppicing the cutting back of trees to stimulate growth and changes to nightingale wintering grounds. Now, a study has found that warmer temperatures have made their wings get smaller a trend that has also been seen in other bird species. 'There is much evidence that climate change is having an effect on migratory birds, changing their arrival and laying dates and their physical features over the last few decades,' said zoologist Carolina Remacha of the Complutense University of Madrid From an analysis of twenty years of data on the birds, her team found that natural selection driven by climate change is causing the nightingale to evolve shorter wings, which could make them less likely to survive their annual migration. A comparison of wing shape variation and survival in two populations of nightingales from central Spain found the bird's average wing length has decreased relative to its body size. Shorter-winged birds were less likely to return to their breeding grounds after their first round-trip to Africa. The researchers linked changes in wing length and reduced survival to a phenomenon known as the 'migratory gene package'. This predicts adaptations related to migration including a long wingspan, higher resting metabolic rate, larger clutch size and shorter lifespan. These are controlled by a set of connected genes, so selective pressures on one trait also affect the others. In recent decades, the timing of spring has shifted in central Spain and summer droughts have become longer and more intense. This has left nightingales with a shorter window in which to raise their young. This means the most successful birds may be those that lay smaller clutches of eggs giving them fewer young to care for. If natural selection is favouring smaller clutches, it may simultaneously push nightingales away from all of the linked traits in the 'migratory gene package.' Evolving smaller clutch sizes and inadvertently also gaining shorter wings and, therefore, a reduced chance survival is an example of what experts call 'maladaptation'. This is where organisms' responses to changing conditions end up being harmful instead of helpful. 'If we are to fully understand how bird populations adapt to new environments in order to help them tackle the challenges of a rapidly changing world, it is important to call attention to the potential problems of maladaptive change,' Dr Remacha said. Scientists have long known that individuals from a given animal species tend to be smaller in warmer parts of their habitat. However, only recently was it conclusively determined that climate change was also triggering shrinking body sizes, with a US team reporting in December that migratory birds in North America have shrunk over the last 40 years. The discovery was based on an analysis of more than 70,000 migratory song birds that had been collected after fatal building strikes in Chicago and Michigan. Slightly larger than a robin, nightingales were first noted in Anglo Saxon times though fossilised remains date them back to as long as 100,000 years ago. The full findings of the study were published in the journal .