Results from the 2014 Early Bird Survey show that birds arrive later to feed in gardens in areas with high levels of artificial lighting, whether in the town or country. Artificial lighting from street lights, advertising signs, homes and offices, is one of the key ways in which humans have changed the environment, particularly in urban areas. There has been much research into the effects of artificial light on birds during the breeding season, especially on the timing of song, but few studies have investigated other behaviours, or the effects of artificial light at other times of the year. Previous work by the BTO has revealed that birds tend to arrive at garden feeders later in the day in winter in urban areas than in rural areas. However, it was not known how this pattern could be affected by the density of artificial lights and whether garden birds would take advantage of increased foraging time provided by extra illumination in very well-lit areas. Now, new research led by Gary Clewley of the BTO’s Demography Team has answered this question. The study used data collected by thousands of volunteers across the UK, who took part in the BTO Garden BirdWatch Early Bird Survey in early-January 2014. This involved observers recording the time at which the first ten species that arrived in their gardens to feed one morning. Additionally, observers noted the number of artificial lights in the area surrounding their gardens. Blackbirds were the first to birds to arrive, followed by Robins and Blue Tits. In contrast to what may have been expected, the study found that birds tended to arrive later where there were more artificial lights present, both in urban but also in rural areas. Therefore, artificial lighting does not appear to be acting against the pattern of later arrival in more urban areas and may actually afford birds slightly less foraging time on winter mornings. The mechanism driving this pattern, is not yet understood, but there are several possible explanations. For example, birds in well-lit areas might forage elsewhere before they visit gardens, or they might forage longer into the evening. Alternatively, they might avoid garden feeders if there is a higher risk of predation in that habitat in well-lit areas. January 2014 was also mild, so birds might behave differently in colder weather. Nonetheless, this study demonstrates another important effect of artificial light on birds. Further research is required to fully understand this phenomenon and how it varies throughout the year. This understanding is critically important, given than urbanisation is increasing globally, and birds and other wildlife are ever more exposed, and forced to respond to, our artificial light.

Newly published research led by the BTO shows a consistent impact of climate change on biodiversity around the world. A new analysis of the results from over 130 previously published studies of wild species, ranging from alder trees to zebras, has found a consistent impact of climate change on global biodiversity. The research, led by BTO scientists working in collaboration with organisations from the Cambridge Conservation Initiative, showed that populations of many species actually respond positively to warmer temperatures, with cold weather associated with population declines, particularly in temperate countries like the UK. However, this positive effect of temperature was largely negated where there was a significant long-term warming trend, demonstrating that climate change is already affecting species' populations. Rainfall was the most important factor influencing species’ populations in tropical and sub-tropical regions, where wetter weather generally has a positive effect. Here again there was evidence that climate change may be negatively affecting species through the detrimental impacts of drought. This study not only indicates that climate change is affecting many species around the world now, but importantly shows that the ways in which climate change affects species varies with location. In the tropics, changes in rainfall and therefore drought conditions will probably have the greatest impact on species’ populations, communities and ecosystems. This means that conservation management to help species cope with climate change in these areas should focus on managing water levels. However, the processes will be different at higher latitudes, where the impact of warming is likely to be more important. The effect of warming in temperate latitudes helps explain why many bird populations in the UK have increased as temperatures have risen, leading to polewards shifts in the distribution of those species. However, in the tropics, we would expect species’ range shifts to be driven as much by changing rainfall patterns as by temperature, and therefore species’ may not simply shift polewards away from the equator. Given that the impacts of climate change upon biodiversity in the tropics are likely to involve different ecological mechanisms from those impacts at higher latitudes, there is an urgent need to establish robust monitoring and long-term biodiversity studies across tropical regions to track the changes that occur. This research underlines the widespread and complex implications of climate change across the natural world, and identifies areas in which further research and monitoring is needed to address and reverse the negative impacts on biodiversity.

BTO research has used data from the Breeding Bird Survey to show that many of our birds have expanded their geographic range as a short-term response to climate change. BTO research, led by Dario Massimino of the Population Ecology and Modelling Team, has used data from the Breeding Bird Survey to investigate the short-term response of breeding birds in Britain to recent temperature changes. Many models of climate change predict contractions in species range and increased extinction risk. This study looked at the period between 1994 and 2009, during which Britain experienced an average temperature increase of 0.59°C. The analysis of the population density of 80 bird species during these years showed an expansion in the majority of these species’ ranges. The paper’s authors examined the northern and southernmost extent of where these species occur in the UK (the range margins), and found that the northern margin had shifted north by approximately 45 km on average. Over the same period, the southern margin had remained largely static, amounting to a northwards range expansion for the species concerned. This research also explored whether species had shifted to higher altitudes as British temperature rose, but found no consistent response. The results of the study show that bird movements are not keeping pace with temperature changes. With the change in temperature recorded, birds were expected to shift northwards by 108 km or upwards by 63 m. Climate change impacts on biodiversity are largely of concern due to the magnitude of future projected impacts, so the absence of short-term adverse effects found in this study should not be taken to mean that climate change will not cause range contraction in many species. Instead, the study underlines the importance of long-term monitoring to detect, document and properly describe the impact of climate change on biodiversity and ecosystems, so that conservation action can be optimally targeted.