Less than a month after Instagram debuted its Vine competitor, Twitter's video-sharing app, Vine, has started to drop off on its own turf. According to data provided to the Atlantic Wire by Topsy, which measures links shared on Twitter, Vine usage has continued to drop since Instavid came onto the scene in mid-June.

The chart only shows links on Twitter, so it's not an exact picture of total usage. But, that's actually worse news for Vine. A lot of Vine sharing happens on Twitter—though, there's an accompanying app—because Twitter owns Vine. 

It also looks like Vine had started tapering off a little before the Instagram announcement. This closer (less complete) look, however, shows a clear drop on June 20th, the day Instavid was born:

It looks, though, as if there has been a minor recovery of "influencer" users, which is what that graph shows. 

Instagram, on the other hand, has a clear disadvantage on that particular platform because its pictures and videos don't show up in Twitter's stream. You have to click through a mystery link to see what lies beyond the URL, making the whole thing more onerous than just posting to your feed, which is now available in an easy-to-browse desktop version, too. That Twitter sharing change went into effect before this chart even begins, last December 2012. But it also might help explain why Instagram hasn't seen a particular spike as Vine has dipped. If people started shifting their sharing from Vine to Instagram, you might not see it in this chart because a lot Instagramming happens off of Twitter.

It's important to note, though, what this chart does not say about Instagram: "The activity on Instagram is so erratic and spiky, it’s nigh impossible to attribute any significant gains to the release of video on the service," as AllThingsD's Mike Isaac pointed out vis-a-vis similar data. In other words, it's not clear if Instagram is eating Vine's users. People could just be getting bored with Vine, or it could just be a summer lull, or something. 

Meanwhile on Instagram, the #RIPVine hashtag that popped up as soon as Facebook made its video announcement is alive and well, with nearly 40,000 posts on Instagram.