2011 is off to a good start for Discovery’s U.S. networks, as Discovery Channel, Investigation Discovery and Science Channel mark January with new ratings records for new and returning series.

Discovery Channel is enjoying its second highest January ever among Men 25-54. The success is thanks to new series Gold Rush: Alaska, Flying Wild Alaska and Sons of Guns, as well as viewer favorites American Chopper: Senior vs. Junior and Dirty Jobs. American Chopper: Senior vs Junior in particular had a great month, with last Monday’s 9pm ET/PT premiere enjoying the highest ratings for the series since 2004, with 3.16 million viewers.

Investigation Discovery, similarly, had its best January on record last month, as it celebrated its third anniversary with double digit year-over-year growth. ID also cracked the top 25 of all ad-supported cable for the month, ranking #22 on Mondays, #23 on Thursdays, and #23 on Sundays among W25-54 in prime delivery. ID will soon launch five new original series in the span of four weeks, including Nothing Personal (which will be hosted by Steve Schirrippa of The Sopranos), exploring the sinister world of contract killings.

Finally, Science Channel scored a big win in January with its new series An Idiot Abroad. Fans have fallen in love with Karl Pilkington (and his round head) and, since its debut on January 22, 4.3 million viewers have watched the series, making An Idiot Abroad the network’s highest rated series ever.

What have you been tuning into on Discovery ‘s nets?