Besides your fieldwork and thesis supervisor, you also need a second reader to evaluate your thesis during your defense.
To make sure your thesis is evaluated as unbiased as possible the dept. of IDS has decided that a second reader should be present during the last fase of your thesis, during thesis defense. He/she will take the lead and will only consult the supervisor for procedural questions.
The second reader is appointed to you and can be a specialist in your thesis topic or region where your fieldwork was conducted.
If your supervisor is from the IDS staff the second reader can be an external person. If you have an external supervisor, the 2nd reader has to be from IDS staff, to make sure all IDS stardarts are met.