The time that birds decide to breed has a strong impact upon the likely success of raising their young to independence. Pairs of birds will generally time egg laying to maximise the availability of food for their chicks. However, one of the strongest impacts of climate change so far has been to alter the timing of spring. In response to milder temperatures, flowers and insects are all appearing earlier than they used to. Songbirds struggling to match their timing to the changing climate could be facing population declines. To test this, BTO, in collaboration with The Woodland Trust, Rothamsted Research, Butterfly Conservation and the Centre for Ecology and Hydrology (CEH), have collated some of the most comprehensive long-term data on the timing of spring from across the UK. They have related changes in the timing of leaf and flower emergence as well as aphid, butterfly and moth emergence, to changes in the timing of egg-laying, tracked by the BTO/JNCC Nest Record Scheme. As expected, in warmer springs, birds do tend to breed late relative to the timing of spring. However, by using data from the BTO/JNCC ringing scheme to monitor changes in the number of fledglings produced by each species per year, the study’s authors found no evidence that these mismatched species were also suffering a long-term decline in breeding success. This suggests that the population declines observed in many British songbirds are not directly caused by the effect of mismatch on breeding success. These results significantly increase our understanding of the impacts of climate change upon birds by showing there is not a strong link between changes in the timing of spring and long-term trends in breeding success. The heroic efforts of thousands of volunteers recording information on birds, insects and plants were vital in providing the long-term data required to understand the impacts of climate change upon bird populations, and we thank them for their hard work and dedication.

There is growing use of full-spectrum bat detectors to survey bats and other taxa. When used in conjunction with call identification software and validation, these detectors have the potential to transform large-scale bat monitoring in the UK. However, there are several questions to be answered regarding how these detectors should be best deployed.

Responding to a request for information on the status of deer in Scotland, BTO researchers Dario Massimino and John Calladine analysed data on Red Deer and Roe Deer distribution and abundance, collected through the BTO/JNCC/RSPB Breeding Bird Survey. This research note describes the derivation of maps of abundance and change in abundance for the two species, from the late 1990s to the present day, and illustrates recent changes in distribution and abundance.

Research commissioned by Scottish Natural Heritage (SNH) and led by the British Trust for Ornithology (BTO) demonstrates the power of volunteers in helping to better understand the distribution of rare and vulnerable bat species. The Southern Scotland Bat Survey was a pioneering citizen science project run in 2016. It aimed to engage the public by allowing people to borrow bat monitoring equipment for a few days to record bat activity. This approach enables the collection of high-quality data on bats, from a wider range of sites, than could feasibly be achieved by professional researchers alone. Focusing on the southern third of Scotland, over 1,500 complete nights of bat recording were carried out across 715 one-kilometer squares, resulting in the collection of just under 400,000 bat recordings. Whilst data were collected for all bat species in the region, more detailed analyses were carried out on three species of bats, Leisler’s bat, noctule and Nathusius’ pipistrelle, because their preferred habitat and foraging behaviour make them particularly vulnerable to wind farms. Of the three species, Leisler’s bat and noctule were found to be more widespread and abundant than previously thought, although they remain localised and amongst the five most scarce species of bats in Scotland. Southern Scotland has one of the highest densities of wind farms in the country. The study has produced detailed data and mapping which will be invaluable in assisting decisions in the region, including assessing future onshore wind energy construction.

Researchers have long investigated the effects that climate change might have on species’ future ranges. However, for the first time, scientists at BTO have used abundance data to project the future distribution and abundance of more than one hundred breeding birds in Great Britain in order to assess how the whole bird community might change as a consequence of climate change. There have been numerous studies on species’ future distributions, where presence-absence or presence-only data were used to predict where species might occur in future in response to climate change. These studies are very useful to identify the most vulnerable species and habitats and therefore aid conservation prioritisation. However, significant population changes can occur without obvious changes in range. Such trends can only be identified using abundance data detailing how bird numbers vary in space and time. Scientists at BTO had previously tested future projections using abundance data for four selected species and in Special Protection Areas. In this latest study, we have produced future projections of distribution and abundance for 124 breeding bird species, including some which are not yet present in Great Britain, but could potentially colonise if they take advantage of higher temperatures. Data from the Breeding Bird Survey (BBS) and its French counterpart (the Suivi Temporel des Oiseaux Communs) were used in this research. French data were included to better quantify the species’ response to climate conditions found in France but yet to occur in Great Britain, and to consider potential colonists such as Melodious Warbler and Tawny Pipit. Future climate change was projected to result in significant population increases for 55 species and significant population declines for 11 species by 2080. This may apparently look like good news, but in reality 6 of the 11 species that are projected to decline are already red-listed in Britain for their recent population decreases (Grey Partridge, Curlew, Grasshopper Warbler, Ring Ouzel, Pied Flycatcher, and Yellowhammer), and 4 are already amber-listed (Red Grouse, Snipe, Willow Warbler, and Meadow Pipit). In contrast, 40 of the 55 species that are projected to increase are either currently green-listed or not yet breeding in Britain. This highlights how climate change will more seriously hit those species that are already of concern. As a consequence of these responses to climate change, different regions of Britain will see net gains and losses in species abundance. Our projections show that the largest gains in abundance will mostly be in northern and north-western Scotland and other smaller areas of western Britain. The south-east show apparent stability, but this is a result of large projected declines in red-listed species and compensating increases in green-listed species. Because of all these changes, community turnover will be high throughout Great Britain, but in particular in the west of Scotland, where changes in abundance of species that are already present will prevail. The analytical methods used provide an important framework to make projections of impacts of climate change on species abundance, rather than simply projected range changes. It has shown us significant changes in community composition that would have been invisible to us had we only used bird distributions. These projections will help conservation practitioners identify species that most urgently require mitigation and adaptation measures and target where those measures may best be adopted.