Project starts for Windows Phone applications among developers using Flurry analytics have increased by 600 percent over the past 12 months. The mobile analytics company is the newest voice suggesting that Microsoft’s platform may be emerging as a viable third option for mobile developers.

According Flurry’s blog post, Windows Phone project starts — defined as setting up an app for analytics tracking before its official launch — currently account for six percent of all new projects the company records. Year-over-year Window Phone apps have gone from accounting for just one percent of Flurry’s starts to four percent — a noticeable increase, but still far behind behind iOS which accounts for 67 percent of all Flurry project starts and Android, which accounts for 28 percent.

What is more telling, according to Flurry is the rate at which iOS, Android and Windows Phone appear to be growing year-over-year. According to the analytics company, Windows Phone has recorded the largest year-over-year growth rate per platform, registering a 521 percent increase. Android takes second place, recording an 82 percent growth rate, with iOS recording a growth rate of 66 percent.

We’ve seen several green shoots this year indicating Microsoft has been turning around the fortunes of its long-beleaguered Windows Phone platform. In January Nokia reported it had sold over 1 million Lumia phones, and analysts have reported steady, if not outstanding sales since. In April Distimo reported the Windows Phone Marketplace was the fastest growing app store, recording the largest quarter-over-quarter growth of any mobile app vendor. Even more tellingly earlier this month ComScore reported Windows Phone had increased its share of mobile subscribers, growing from 3.9 percent of the market to 4 percent — a modest gain, but one that came after several months of declines.

While Windows Phone is still a minority player in the mobile app market, it is becoming increasingly apparent Windows is increasing the platform’s support, both with developers and customers. We’ll continue to monitor Microsoft’s progress carefully.