NEW YORK (TheStreet) -- If you were wondering why you weren't so productive over the past month, you may want to look at how much time you spent checking Facebook (FB) - Get Report on your phone.

The average visitor to Facebook's mobile site or app spends roughly 49 minutes there a day, according to comScore. This means that Facebook accounts for about a third of all the time people spend visiting social media networks on mobile.

Every month Cowen and Company tracks metrics for the social media apps it covers, including Facebook, Instagram, Twitter (TWTR) - Get Report, Pinterest, Yahoo! (YHOO) -owned Tumblr, LinkedIn (LNKD) , Snapchat and Tinder. This social universe as a whole saw good growth in April, with the total mobile app unique visitors increasing 1% month over month, but Facebook saw stellar growth.

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Menlo Park, Calif.-based Facebook added 3.4 million unique visitors in April, and Instagram, which Facebook owns,, added 3.8 million unique visitors.

LinkedIn showed the strongest growth of unique visitors in terms of percentage, increasing 26% over March. Snapchat grew 10%, Tumblr grew 9%, Twitter and Pinterest each grew 7%, and Tinder grew 5%.

Facebook also led the pack in terms of engagement with its app. Of the 49 minutes a day users spend on Facebook's site and app, 44 minutes of those are on the app, a 55% increase year over year and an 8% increase month over month. This marks a new high since Cowen started tracking in December 2012.

On Facebook's first quarter earnings call, CEO Mark Zuckerberg noted that "Facebook and Instagram get more than one out of every five minutes spent on mobile," with people spending an average of 21 minutes a day on Instagram.

Instagram grew engagement 5.5% month over month, and both Tinder and Snapchat grew 4%.

Facebook's dominance in mobile isn't terribly surprising given the popularity it has with teenagers, who tend to spend more time on their phones. Recent numbers from the Pew Research Center show that 71% of teens use Facebook, 52% use Instagram, 41% use Snapchat, and just one-third use Twitter.