By Chris Dieterich 
 

NEW YORK--When Twitter Inc.'s shares start trading, which is expected Thursday morning, no exchange-traded funds on the market will own the stock out of the gate. But a pair of ETFs are set to add the stock next week, and others are plotting to catch the stock in the months ahead.

One ETF likely to buy Twitter at the Oct. 13 closing bell, just following what would be the stock's fifth day of trading, is the $98 million Global X Social Media Index ETF (SOCL), according to a spokesman for the ETF provider. The Global X ETF has had a mammoth year, climbing 51% on the backs of strong performances from Facebook Inc. (FB), LinkedIn Corp. (LNKD), Yelp Inc. (YELP) and a Chinese counterpart to Twitter--Sina Corp. (SINA), according to Morningstar.

Another is an ETF launched on in the last month: The $29 million Renaissance IPO ETF (IPO), which is stewarded by initial-public-offering research-and-investment company Renaissance Capital LLC. Like the Global X fund, Renaissance Capital's ETF can buy IPO stocks as soon as after the fifth trading day, though it can also wait longer, according to the ETF's prospectus. This fund can pick IPOs that hit the market with over $100 million in market value, and top holdings include Facebook, Zoetis Inc. (ZTS) and Michael Kors Holdings Ltd. (KORS).

One ETF that is likely to wait longer before buying Twitter is the $250 million First Trust US IPO Index ETF (FPX), the first IPO-related ETF on the market. This ETF requires more seasoning in the stocks it buys. But its index methodology means that it could add Twitter shares as soon as the close of trading on Dec. 20, according to the ETF provider.

While the slow play in IPO buying misses out on the first-day pop, it also skips some of the noise associated in early IPO trading, says Josef Schuster, founder of IPOX Schuster LLC, the research-and-investment firm that provides the index for First Trust IPO ETF.

The First Trust IPO ETF took its time to buy Facebook last year, and to great effect. Mr. Schuster bypassed his first chance to buy Facebook in the summer of 2012 amid concerns that corporate insiders selling shares might dilute the social-media company's stock price, he says.

Instead, the ETF picked up shares of the company in September 2012. Since then, Facebook, the ETF's largest current holding, has more than doubled. The First Trust US IPO Index ETF is up 45% over the past year.

Mr. Schuster says he is still undecided about Twitter, and says it will look a lot less attractive if strong demand pushes the stock price sharply higher.

"We generally don't include companies that have strong pop of more than 60%," he says.

Write to Chris Dieterich at christopher.dieterich@wsj.com

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