Bird had denied wounding Milligan with a glass after a row at their Cronulla home in August 2008.
Magistrate Roger Clisdell said he didn't think that Bird really showed regret for hurting his girlfriend despite a character reference she had wriiten in an attempt to persuade the court to be lenient.
Bird's friend Brent Watson, whom had been originally named by Bird as being responsible for the cuts to Ms Milligan, described the rugby star as "selfish".
However, for Bird's defence his lawyer, Les Nicholls, explained that his client had not hurt Milligan intentionally and had not caused her any lasting harm.
Bird and Milligan have been living together in France where he had been signed to the Catalans Dragons.
The Catalans Dragons began talks with the intention of keeping Bird on with the team after he had been convicted back in April.
