This is probably on the whole population, so predominantly male immigration is likely the main reason.

The map is not very helpful about what is actually depicted but wikipedia has similar data with a breakdown by age :

https://en.m.wikipedia.org/wiki/List_of_sovereign_states_by_sex_ratio

Qatar for instance is not very high (this is a ratio of number of male over number of female) on the "at birth" and "0-14" age bracket with 1.02. it's actually a bit lower than western countries.

The data is still concerning in some countries with notably larger "at birth" ratio and even an increase in th "0-14" age bracket.