The 'Where Eagles Lived?' project launched in September 2017. Five months on, we have completed our data collection and finalized our results.
Before the 'Where Eagles Lived?' project launched, the historic data for White-tailed Eagles (WTE) and Golden Eagles (GE) in Wales was very limited. Wales has been poorly served in the way of written historic records for most raptor species. Particularly for GE and WTEs, as both species became extinct in Wales before the growing interest of bird recording in the 19th Century.
The 'Where Eagles Lived?' project is the first attempt to produce an authoritative evidence-based assessment of the historic distribution of Eagles in Wales. It quickly became apparent, the use of historic ornithological written records alone, revealed an enormous gap in our knowledge and understanding of the historic range for both species prior the 20th Century. From our initial search, we could only find 23 suitable historic records for both species. However, by expanding our sources and applying statistical modelling to our historic data-set, we now have 166 historic records for both species in Wales.
There are a number of relevant methods to assess the past eagle assemblages in Wales. We used a number of complementary data sources to collect historic records for eagles in Wales, including: 1) written historical accounts; 2) Welsh place-names; and 3) supporting records, including archaeological findings, persecution records and museum specimens.
We had a number of challenges with our final data-set. Out of our 166 historic records, 48.2% of records indicated the presence of an 'eagle' species. In order to assess the relative historic distribution of both species of eagles in Wales, we needed to utilize the full extent (n = 166) of our historic data-set. The high percentage of records that were not identified to species level (i.e. a GE or WTE) is an attribute of place-name records. All welsh place-names included the component 'eryr', 'eryrod' and 'heryr' (i.e. welsh deviations of the English word for 'eagle'), which indicated the presence of either a GE or WTE.
Therefore, in order to estimate the historic distribution of both species, utilizing the full extent of historic records, we decided to turn our attention to the historic habitat. A variety of distinct historical environmental features were collected for each historic record. Environmental features were carefully selected to represent habitat preferences of both species. For example, European WTEs tend to prefer coastal, wetland, and lowland areas with trees, at lower altitudes in close proximity to water sources than GEs. Thus, applying modern knowledge of habitat preferences to our 'known ID' historic records enabled us to shed light (through statistical modeling of course!) on trends within the distribution data for each species.
Environmental features associated to the habitat preferences of GE and WTE were then applied to the 48.2% of 'uknown ID' records within our data-set. All place-name records were assigned a species ID, allowing us to robustly assess the historical distribution of each species of eagle across Wales. The final data-set comprised of 166 historic records, 89 for GEs and 77 for WTEs. The proportion of historic records collected for each source type is shown below for each species (Figure 1).
Figure 1. The proportion of historic records collected between source types for Golden [top] and White-tailed Eagles [bottom] in Wales.
For our distribution analysis, we also looked at the number of historic records within each preserved county. There are eight preserved counties in Wales: Gwynedd (including the Isle of Anglesey), Clywd, Dyfed, Powys, West Glamorgan, Mid Glamorgan, South Glamorgan and Gwent. Our official results are in the form of historic distribution maps for both species. Unfortunately, we are restricted to release these maps until the research has been published. On the brighter note, who doesn't like a good 'old fashioned' pie chart.
Our tentative reconstruction of the historic distribution of eagle species suggest that both species were widespread across Wales. All eight preserved counties in Wales held historic records for an ‘eagle’ species, with the north-west and north of Wales holding 54.2% of eagle historic records. There were slightly less historic records found for WTEs (n = 77), in comparison to GEs (n = 89) in Wales. Despite slightly less historic records for WTEs, results revealed the WTE to have more of a broader historic range to GEs (Figure 2). Golden Eagle historic occurrence highlights Gwynedd particularly the Snowdonia range, parts of Clwyd and north of Powys as core historic areas for this species. White-tailed Eagle historic distribution revealed strong historic use in areas of Wales such as: Gwynedd, including Isle of Anglesey; parts of Dyfed, mainly the Ceridigion Coast; West Glamorgan, predominantly the Kenfig and Swansea coast; and ranges of Mid Glamorgan. There were no historic records for GEs in Mid Glamorgan or for WTEs in South Glomorgan (denoted in 'red' in Figure 2).
Figure 2. The proportion of historic records collected for White-tailed Eagles [top] and Golden Eagles [bottom] between Welsh preserved counties.
It can now be concluded that both species were historically widely distributed across Wales, potentially occurring wherever their ecological requirements were met. This is a great start for the ERW project, as the lack of historic data for eagles have impeded eagle reintroduction programmes for Wales in the past. As part of strict criteria, regulated by the IUCN reintroduction guidelines (2013), any release sites for either species of eagle in Wales should be within their historic range. The ERW team is more than satisfied that we have, at least, answered the most problematic IUCN reintroduction guideline.
Our historic data-set ranges from the pre-historic Neolithic period (12,000 – 2,750 BC) to the early 1900s. Breeding ceased in Wales for GEs in the 1850s, with their last breeding site recorded in the Snowdonia range, Gwynedd. Shortly after, in the 1860s WTE breeding ceased in Wales, with the last known nest to be located in the Kenfig National Park, West Glamorgan. Historic sightings after breeding ceased in Wales, can be suggested to be 'floaters' or 'immature' eagles either remnants of the Welsh population or migrating eagles from the northern regions of the UK.
The ERW team would like to thank everyone who sent us data for the 'Where Eagles Lived?' project, your support and efforts are much appreciated. We are dedicated to assessing the feasibility of bringing two of our native lost eagles back to their historic home in Wales. We are currently engaged in a range of research questions shaped to address strict IUCN reintroduction guidelines. We are excited to share how the project develops over the next three years. We aim to report on the any progress at key stages of the project.