After showing caution last month, short sellers seemed to be prompted into action in the first two weeks of this month by the overbought markets, the political and geopolitical uncertainties and the rising concerns about a sizable market correction. Moves in the most shorted stocks traded on the Nasdaq were mostly upward between the April 28 and May 15 settlement dates.

Leading that trend was semiconductor company AMD, with a double-digit percentage rise in the number of its shares short during the period. On the other hand, bucking that trend were biotech companies Opko Health and Synergy Pharmaceuticals.

Note that still only three Nasdaq stocks had more than 100 million shares short, as of the middle of this month. However, two of them remain very far ahead of the pack.

Frontier Communications

After retreating marginally in the previous period, the number of shares short in Frontier Communications Corp. (NASDAQ: FTR) rose more than 5% to more than 270.49 million as of the most recent settlement date. That was 23.2% of the telecom’s float, as well as the 18th consecutive period with more than 200 million shares short. The daily average volume rose sharply, so the days to cover dropped from around nine to less than five.

During this latest period, Frontier finally announced the long-feared dividend cut. The share price tumbled more than 31% in the first two weeks of this month. The stock has recovered a little since then, and closed most recently at $1.37 a share. It hit a 52-week low of $1.19 at the end of the short interest period. The 52-week high of $5.30 was seen about a year ago.

Sirius XM

The more than 252.10 million Sirius XM Holdings Inc. (NASDAQ: SIRI) shares short by the middle of May was less than 1% higher than on the previous settlement date. It was only the fourth period so far this year in which the number of shares short has grown, and the most recent figure represented 16.9% of the total float. As the average daily volume plunged from a year-to-date high, the days to cover jumped from less than six to nearly 10.

Warren Buffett remains an investor in Sirius during, both directly and indirectly. The stock ended the initial two weeks of the month more than 3% lower, while the Nasdaq climbed less than 2% between the settlement dates. After hitting a 52-week high of $5.53 in March, the stock closed on Wednesday at $5.11 a share. The 52-week low of $3.74 was seen last summer.

AMD

By the middle of this month, Advanced Micro Devices Inc. (NASDAQ: AMD) had more than 146.13 million shares short. That was a gain of nearly 21% from the total on the previous settlement date. It represented 17.5% of the company’s float, and it was by far the highest level of short interest in at least a year. It would take less than two days to cover all short positions.

Analysts had mixed reactions to AMD’s most recent quarterly results. While the May 15 share price was around 14% lower than on the previous settlement date, it was down more than 24% at one point in the interval. The stock closed at $10.89 on Wednesday, about 4% lower year to date. Shares have changed hands at between $3.88 and $15.55 in the past year.