[@robin-w Moderator 13 years, 3 months ago]

Firstly, you need to post this on the theme’s support site

https://wordpress.org/support/theme/blackbird

Since this site has a free download trial version and a bought version, I suspect you may need to spend $45 to buy this version to take this ad out – don’t guarantee that, but suspect it is the case.

see
http://www.inkthemes.com/wp-themes/blackbird-responsive-wordpress-theme/