A burning question: how does timing of breeding of upland birds affect risk posed by moorland burning?
17 Feb 2022 | No. 2022-05
There is considerable public interest in how our uplands are managed, one area of concern being about the potential for rotational burning of vegetation to impact on nesting birds. Rotational burning is a common form of land management in the UK uplands and is restricted to the colder half of the year, with the time period during which burning may be carried out varying between countries. In England and Scotland, burning can take place from the 1st October to 15th April, but in the latter, permission can be granted to extend the burning season to 30th April. In Wales, this period runs from 1st October to 31st March. What implications do these timings have for the birds that breed in these areas?
This question was addressed in a study funded by Natural England and DEFRA, and carried out by the British Trust for Ornithology (BTO) and the Game & Wildlife Conservation Trust (GWCT). Their report confirms the findings of many other studies that laying dates of most species have advanced (got earlier) in recent decades. Despite this, there is relatively little overlap between the current burning seasons (the period during which burning is permitted) and the nesting attempts of most upland birds.
That said, the overlap of the burning season with the nesting attempts of some early-breeding species, including Peregrine, Lapwing, Golden Plover and Stonechat, is higher. Many birds of these species start breeding before the end of the main burning season in England and Scotland. The proportion of breeding attempts overlapping with the burning season varies from 41% for Stonechat to 82% for Peregrine. In some parts of Scotland where burning is permitted until the end of April, this overlap is likely to be higher.
However, overall risk for populations of these species turns out to be very low. Most upland Peregrines nest on crags that are unlikely to be subject to moorland burning. Lapwings and Golden Plover are also unlikely to be directly impacted by burning. Burning management typically targets older stands of heather, knocking back tall, woody stems and promoting fresh growth for Red Grouse to eat. Because Lapwings and Golden Plovers prefer to nest in short vegetation, the areas they nest in are unlikely to be selected for burning.
Stonechats often nest in scrubby vegetation, including older stands of heather that may be selected for burning. However, because Stonechats are widespread, breeding in many areas outside of managed moorlands, the proportion of Stonechat nests likely to be destroyed by moorland burning each year in the UK is well under 1%. In some stable and increasing populations of Stonechat, more than half of all nesting attempts end in failure, so such a small proportion failing due to moorland burning is not unlikely to impact much on overall numbers of Stonechats in the UK.
By contrast, moorland areas managed by rotational burning are disproportionally important for Merlin and Ring Ouzel. Because they start nesting later than Stonechats, burning within the standard upland burning season in England and Scotland (finishing in mid-April) is unlikely to pose a serious population-level risk to these species. However, extending the burning season to the end of April, as can be done in Scotland, increases this risk considerably for both species. If burning is carried on until the end of April across all moorland in England and Scotland, the population-level risk of burning activity to Merlin and Ring Ouzel would rise to 6–7% in England, and 4–5% in Scotland. Such losses could be significant, particularly at a local or regional level, especially for species like these whose populations are already declining.
Threats posed by moorland burning to breeding birds probably vary between different parts of Britain. Mark Wilson, Senior Research Ecologist at BTO Scotland said, “Within the past 10 years, the end of the upland burning season in Wales has been brought forward by 15 days to 31st March. This is likely to have virtually eliminated the direct risks of nest destruction posed by heather burning to Welsh upland bird populations. The area where moorland burning within regulated dates could now pose the greatest threat to breeding birds, particularly to Merlin and Ring Ouzel, is probably southern Scotland. Here, the timing of breeding of many birds is similar to that a little further south, in northern England. However, burning in some areas may be permitted up to the end of April, two weeks after the upland burning season has closed in England, and a month longer than burning in Wales is permitted.”
The data used in this study were drawn largely from the Nest Record Scheme (NRS), an initiative run by BTO and supported by hundreds of volunteers, who contribute information on thousands of bird nesting attempts to the scheme each year. Alistair Crowle, Senior Environmental Specialist with Natural England said, “This report demonstrates the value of long-term data sets like the BTO’s Nest Record Scheme that allow us to investigate the phenology of species, in this case, upland birds in a warming climate. This enables us to evaluate the effect of anthropogenic activity upon nesting birds and if necessary, modify or respond to that activity.”
When reviewing burning regulations, decision-makers will need to consider a range of factors, including regional variation in both the nesting phenology of birds and the number of days suitable for burning. Kathy Fletcher, Senior Research Assistant at GWCT said: “The report identifies that many moorland species were more abundant in areas with burned moorland than in those with unburned moorland. This underlines the significance of controlled heather burning as an important tool to provide the mosaic of habitats favoured by many upland bird species, as well as to reduce the risk of devastating wildfires. It is reassuring then, that this study finds that the majority of heather burning happens before most nesting attempts occur. Nonetheless, best practice burning guidelines recommend that areas are surveyed prior to burning or cutting to locate nesting sites of protected species and for some protected species in Scotland that are sensitive to disturbance, burning and cutting are not carried out after the 1st January within 1km of their nest sites."
The report will help decision-makers to evaluate the impacts of current regulations, and to assess whether changes are needed. The full text of this report, BTO Research Report 741, can be accessed here.
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