I want to know the answer to the following question:
What is the period of breeding during which one of the adult birds is always present at the nest?
All the background I'm provided with is that "At the other extreme, many seabirds have extended periods of parental care, the longest being that of the great frigatebird, whose chicks take up to six months to fledge and are fed by the parents for up to an additional 14 months.". Is that enough to answer the question?