This page summarizes the general techniques for performing a taxonomic split in Avisys. There are two kinds of split; one where a species is split into entirely new species and the old species no longer exists, and one where part of a species is split into a new species but the old species still exists. We'll use the split of Northern Goshawk into American Goshawk and European Goshawk as an example of the first kind of split, and the split of Cuban Bullfinch into Grand Cayman Bullfinch and Cuban Bullfinch as as example of the second kind of split.
Of course, you don't need to do anything at all if you have no sightings of the split species, so we'll assume here that you have sightings of Northern Goshawk and Grand Cayman Bullfinch.
You only need to prepare in advance for the first kind of split, so here we'll only talk about Northern Goshawk. First, rename the species to one of the split species. If you have sightings of both of the split species, never mind that until later; for now just rename the species to the split species for which you have the greatest number of sightings. So, if most or all of your Northern Goshawk sightings are in the range of American Goshawk, rename the species to American Goshawk. To rename a species, highlight its name (by clicking on it), click on Edit->Edit Species/Family Name, change the name, and click OK.
For the Cuban Bullfinch/Grand Cayman Bullfinch type of split, there is nothing to prepare in advance.
How to do this is described here.
If you have only seen American Goshawk but not European Goshawk, you are done with that split now. Likewise if you have only seen Cuban Bullfinch but not Grand Cayman Bullfinch, you are done with that split. If you have seen both of the split species, you have a little more work to do.
First, find European Goshawk and click on the name to highlight it. Then, either press Ctrl-F3, or equivalently click Utilities->Save Species for Edit. Either way, this will bring up a "Saved Species" dialog listing European Goshawk. Just click OK here. Then do a List Records of all of your sightings of American Goshawk in the range of European Goshawk. Change each of these records to European Goshawk. To do this, click on the first sighting and then click on Edit, and then on Species. Clicking on Species will bring up the Saved Species dialog that you saw before, and you then click on European Goshawk, and then on OK and Finished. You have now changed the species associated with this sighting from American Goshawk to European Goshawk. If you have a second sighting, highlight it and press enter, and then choose Yes for the question "Do you want to do mass modifys?", and then simply press enter on each subsequent sighting to perform the rename. Repeat this process for each relevant Place. The whole process is simpler than it sounds.
For the Grand Cayman Bullfinch type of split, the process is similar. Do a List Records showing all of your Cuban Bullfinch sightings that should be changed to Grand Cayman Bullfinch (e.g., select by Place) and move them all to Grand Cayman Bullfinch using the same procedure as described above.