[Grammar] A type of bird or birds?

[savemyenglish]

Should I say 'a type of bird' or 'a type of birds'?
And then which of below expressions are correct:
two types of bird/birds?
a special groups of person/people?
several types of job/jobs?

Thanks a lot!

 

[SoothingDave]

Follow singular with singular and plural with plural. A type of bird. Two types of jobs.

You can't say "a special groups." "Groups" is plural, while "a" denotes a singular.