We are currently in the sixth mass extinction, with thousands of species heading towards extinction due to anthropogenic (human-mediated) climate change.
Even in the era of COVID-19, where many people struggled with health, both mental and physical, many took solace in their dawn chorus at home. Though you would think the pandemic may lessen the hard-hitting impact of a warming climate, climate change is still perceived as a much bigger threat to the future than COVID-19, with people in the UK and US citing it as a constant worry.
Songbirds have displayed changes in reproductive success and migration which have been attributed to the changing climate, so we offer insight and tips to reduce your carbon footprint and ease the burden.
Reproduction is expertly timed to coincide with the emergence of prey like flying insects or caterpillars, to provide chicks with plentiful food for the best chances of success. However, warming climates have caused birds to start laying earlier, often around 2 weeks earlier than they historically laid. Research conducted in the US showed a third of species examined advanced their laying dates by over 2 weeks.
Experiments on blue tits have shown for every +1°C, there is stronger selection by blue tits to lay earlier, and the number of fledglings was negatively correlated with the number of very hot days during the nestling phase.
Extreme weather events and even small fluctuations in temperature of ~1.5°C influence the survival of chicks, with a decrease in the size and weight of offspring that do survive.
Over 57% of recorded occurrences of extreme weather in a 2018 global study showed that birds have a negative response to these extreme events, with reduced reproductive success, survival and in some cases huge population declines.
A 2004 study on song thrushes found the summer weight of both adults and chicks were negatively related with dry soils; adults would have to go further to find food causing increased risk of predation and reduced condition. The additional loss of favourable habitat such as damp ditches and hedgerows reduced food sources and increased chances of predation.
Similar issues beset the reed bunting where winter survival rates are probably the main cause of their decline. The widespread use of herbicides has reduced availability of the small weed seeds these buntings feed on, leaving them under nourished and no longer able to unable to survive severe cold snaps and the long dry winters which are becoming a feature of the UK as climate change progresses.
Studies have shown that birds that arrive early may also stay longer, with a recent 2020 study on reed warblers finding that breeding periods of females have extended by 2 weeks and produce 75% more fledglings compared to the 1980s. The proportion of females raising second broods increased from 2.7% to 23.6% between the first and the second study period while the share of females that did not produce any young annually decreased from 48.1% to 15.5%. The higher offspring production in recent years was related to more successfully fledged broods and an earlier start of breeding, which secured more time to re-nest.
Adversely, Swifts also arrive early and could benefit from a longer breeding season but have been found to suffer terribly due to extreme spring weather events. This is probably due to their morphology, being less able than other species to bounce back. A 2006 study found that inclement weather during breeding season also caused a marked reduction in breeding success in the following year.
A 2017 study found reed warbler adult survival was negatively impacted by these conditions and a 2016 study found Meadow pipits and Chiffchaffs were being squeezed into smaller and smaller winter sites and may have to adapt and evolve and travel further to find suitable habitat in new locations. Interestingly, a common theme in the studies points to winter survival of adults as one of the main indicators of species population changes.
A 2007 study on 10 UK resident species concluded “strong effects of weather on the survival rates of national bird populations” while a 2021 study found that wintering bird communities are tracking climate change faster than breeding communities – birds are not just biodiversity indicators, but also climate indicators.
While this can sound all doom and gloom, it’s not too late to act. If we all do our bit, we can make real and positive change to our planet. The UK government has pledged to work towards being net zero by 2050, where we limit our carbon emissions as much as possible so that the emissions produced are removed by natural means (forests) or carbon capture technology. SBS has five top tips to reduce your carbon footprint:
To help our birds cope with the challenges climate change provides, we also have some tips to making their life easier, with our top five below.
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