Performance Delimiter Vs. Fcsvparser

Hi 

I would like to know, why would fcsvparser taking more time to complete compared to delimiter as below:

dbadmin=> copy fs.columnar_tbl1 from '/home/shared/300MB.csv' delimiter ',' skip 1;
Rows Loaded
-------------
261607
(1 row)

Time: First fetch (1 row): 26819.648 ms.

dbadmin=> copy fs.columnar_tbl2 from '/home/shared/300MB.csv' parser fcsvparser();
Rows Loaded
-------------
261607
(1 row)

Time: First fetch (1 row): 58866.387 ms.

Many Thanks