The Arran Banner reported recently (28th December 2019) on the journey of a short-eared owl between Arran and Morocco. This owl is part of the Short-eared owl Tracking project that the British Trust for Ornithology (BTO)https://www.bto.org runs, and which we find out more about below. The project is a fascinating and important way to understand the migration patterns of these birds, and also hopes to shed light on the recent decrease in their population.
Short-eared owls appear to be nomadic, breeding almost prolifically in suitable habitat in some years, yet in others appearing to be absent. Adults owls can be seen flying during daylight hours when they have dependent young, but at other times they can be largely nocturnal, making the population hard to monitor. The best evidence that we have suggests that the population has declined, perhaps by as much as 50%. The reasons underlying these changes are poorly understood, but recent advances in technology have presented new opportunities for research.
The BTO’s Short-eared Owl tracking project aims to find out more about their fine-scale habitat requirements in order to provide advice on how best to create and maintain suitable conditions. We also aim to better-understand how factors such as prey, predators and competitors influence how they use otherwise apparently-suitable habitats. Given their nomadism, we need to know more about their migration strategies, connectivity between apparent populations, and to better-understand how they find often variable and patchy resources. By carrying out this research we will be able to provide guidance to policy-makers and land managers which will help to secure the future for Short-eared Owls and the environments they inhabit.
Method and approach
We are using state-of-the-art GPS tracking devices to follow several birds over a number of years. These tags are solar powered and record the birds’ locations to within an accuracy of a few metres. So long as they receive enough light to charge the battery, the tags record precise fixes every three hours (less frequently during dark winters), then relay these to the project scientist, John Calladine. This technology gives us information about habitat use and behaviour in unprecedented detail. The tags are fitted to adult birds caught at or near their nests, or on their wintering grounds.
So far, BTO working with local collaborators has tracked nine Short-eared owls in Scotland since 2017. All have provided detailed information on habitat and landscape use, and some have gone on to show astonishing movements and behaviours which differ markedly between birds and also by the same bird between years.
A female tagged in Stirlingshire in 2017 overwintered locally, then undertook a wide-ranging exploratory flight within Scotland before settling down to breed again in Perthshire in March 2018. Not long after her chicks had hatched she left her mate to continue feeding them and flew to Norway, where the tracking data strongly-suggest that she bred for a second time within the same year. The tag then tracked her movements to Ireland, Cornwall and Norfolk, before recording her final hours as she attempted to migrate back to Norway in spring 2019, sadly perishing in storm close to the Norwegian coast.
Another breeding female, tagged at her nest site on Arran in June 2019, visited Bute, Kintyre and Ayrshire before flying south to Devon. On 9th November 2019 she flew south once more, and with the help of a strong tail wind she travelled 495 km into France in just six hours – that’s an average of 82.5 km/h! She then continued south, crossing the Pyrenees on 13th November and the Strait of Gibraltar on 24th November to reach Morocco. It will be fascinating to see where she goes next.
The project aims to track up to 25 individuals from sites across their breeding range in Britain. By tracking birds from a range of locations we can better-understand how variation in local conditions affects their breeding success. Factors such as habitat composition, prey and predator density are all likely have a bearing on the owls’ reproductive output.
The fieldwork necessary to find Short-eared Owl nests is time-consuming, and the tags can only be fitted by highly-trained specialists. This limits the number of tags that can be fitted in a single breeding season (typically May-June), so instead we aim to tag three to five Short-eared Owls each year for the next few years
How you can help
To fulfil the potential of this work, and ensure valid information is available to those who can apply the findings to help Short-eared Owls, we need financial support. The cost of our tagging programme is £97,000, including equipment, fieldwork at different sites, analyses of results and dissemination of findings. Each satellite tag costs £2,000 to buy and the annual data costs are £1,000. Please support the Short-eared Owl appeal https://www.bto.org/how-you-can-help/help-fund-our-work/appeals/short-eared-owl-tracking-appeal if you can.
Read more about the project here (PDF)
For more information about the British Trust for Ornithology and other projects they are working on, see the website
Featured image of a short-eared owl, credit to Liz Cutting 2019.