What is the plural for ibis?

There are two accepted forms for possessive singular nouns ending in s:

Add an apostrophe (') after the existing s at the end of the Word: ibis'

Add an apostrophe s ('s) after the existing s at the end of the Word: ibis's

Examples:

This ibis' nest has three eggs.

This ibis's next has three eggs.

Note: If you are a student, use the form that is preferred by your teacher.