We have just launched the IOC World List on BUBO Listing. This has been requested by many BUBO Listers and we feel it is likely to be adopted by most as their preferred world listing authority. We have also included species distribution details for all species to make it easier to understand the taxonomic differences between this and the Clements World List.
If you already have a world list on BUBO Listing based on Clements it is very easy to convert this into an IOC one. Just use Create New List as normal and ensure you use the "Copy from existing list" option, and specify your Clements world list. Where possible we have mapped taxa between IOC and Clements so it is likely that more than 90% of your list copy will be automatic. Where taxonomic treatment differs you will need to add the appropriate IOC taxa manually, using Batch Edit or View/Edit Species under My Lists. We have enhanced the list copying so that those species that cannot be mapped automatically are emailed to you so it is easy to add them to your new IOC world list at your leisure.
Of course if you don't already have a Clements world list then just Create New List as normal and we suggest pouring yourself a drink as you begin the task of entering all your records! Naturally it takes a while for big world lists, but it is a fun job to do, interrupted by pleasant reminiscences of past birding trips worldwide!
We have also compiled a basic summary of the taxonomic differences between the Clements and IOC world lists.