Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of mortgage REIT HatterasĀ Financial (NYSE: HTS) briefly fell as far as 14% in intraday trading this morning on a sudden volume spike, but they recovered to a milder 4% in short order.

So what: Though it is earnings season, Hatteras' quick dip had nothing to do with quarterly reports. Other REITs including MFA Financial (NYSE: MFA), Two Harbors Investment (NYSE: TWO), and Invesco Mortgage Capital (NYSE: IVR) followed a similar pattern, indicating an industrywide event. In fact, mortgage-bond repo rates jumped this morning to levels not seen since January, causing a panic across markets sensitive to that metric -- such as Hatteras.

Now what: Opportunistic investors pounced on the price weakness, lured by the promise of even higher dividend yields on already generous payers. That's good enough to drive share prices back into more respectable territory. Just be careful out there: Annaly Capital Management (NYSE: NLY) might be solid enough to attract Foolish buyers, but not every REIT -- or its dividends -- will survive the financial storm that started in 2008 and just refused to die.

Interested in more info on Hatteras Financial? Add it to your watchlist.