The British Trust for Ornithology (BTO) and The Royal Society for the Protection of Birds (RSPB) are project partners in the ACCLIMATISE project, supported by PEACEPLUS, a programme managed by the Special EU Programmes Body (SEUPB). ACCLIMATISE is led by the Agri-Food and Biosciences Institute (AFBI). Within this project, BTO is leading Work Package 2: ‘Transboundary Conservation Strategies and Sustainable Management of Marine Predators’. RSPB and BTO are co-leading the ornithological work within the project; this specifically includes seabird tracking and diet analysis, at sea surveys, passive acoustic monitoring, and developing a transboundary seabird conservation strategy and action plans for priority threatened seabird species. BTO and RSPB are looking for suitably qualified and experienced companies to Tender for the provision of Working at Height (WAH) expertise as part of the ACCLIMATISE project between May and August 2026. BTO and RSPB staff are trained as Industrial Rope Access Techniques Association (IRATA) Level 1 Operatives and for each Lot in this Call for Tender (CfT) are seeking field supervision from IRATA certified technicians (Level 3 and Level 2). The work will be focused on facilitating access and supervising researchers at seabird colonies across Northern Ireland. Specifications for the work are split into two Lots, Lot 1, led by BTO and Lot 2, led by RSPB. In both cases, the work carried out by the Supplier will be the same, namely enabling the safe access of Level 1 trained BTO and RSPB staff to seabird colonies in coastal locations in Northern Ireland in order to catch birds for GPS tagging as part of the ACCLIMATISE project. The primary difference between the Lots is the location of work. In both cases, the first two weeks of catching work will be located on Rathlin Island (55.29238, -6.19234), where BTO and RSPB will be working as a single unit. However, for the final two weeks BTO and RSPB teams will be split, with RSPB continuing to work on Rathlin, and BTO moving on to colonies located in Portrush (55.19821, -6.67199) and Newcastle (54.18917, -5.87803). This will result in the contractor supplying IRATA Level 3 and Level 2 support on Rathlin to a single team at the start of the field season but once BTO leave the island, concurrent Level 3 and Level 2 support will also be necessary on the mainland.