Increasing adoption of big display smartphones is having a negative impact on tablet sales, with an IDC study forecasting 2014 as a challenging year for the portable computing device.

Total shipments are down year over year as of last quarter though Apple and its iconic iPad remain the tablet leader with 30 percent of market sales, according to IDC.

"The rise of large-screen phones and consumers who are holding on to their existing tablets for ever longer periods of time were both contributing factors to a weaker-than-anticipated quarter for tablets and 2-in-1s," said Tom Mainelli, IDC program VP of devices and displays.

"In addition, commercial growth has not been robust enough to offset the slowing of consumer shipments."

The news comes as smartphone fever continues to rage among consumers and new vendors, the latest being Amazon, move into the market as longtime players strive to push more feature-rich smartphones into the marketplace. Both Sony and Samsung are prepping to debut new handsets this month and leaks about Amazon's first smartphone, likely due in early summer, are becoming a daily occurrence.

The IDC report released Thursday reveals tablet shipments increased 3.9 percent compared to a year ago first quarter. Apple shipped 16.4 million, a drop of 16.1 percent compared to year ago. Apple blamed inventory flux as the prime reason for the decline.

Yet Apple's iPad accounts for 32.5 percent of all tablets shipped in the first quarter, with Samsung right behind with 22.3 percent market share. Samsung, though, enjoyed a 32 percent spike in growth compared to a year ago.

But while Apple is enjoying market leadership the real winner in the smartphone war is the Android OS as two thirds of tablets shipped featured the open source platform. Microsoft's Windows tablets aren't nearly as popular, according to IDC.