It wasn't a great summer for bird producers.

Despite lower grain prices and steady demand for chicken, the performance of producers like Pilgrim's Pride (NYSE:PPC), Tyson Foods (NYSE:TSN), and Sanderson Farms (NASDAQ:SAFM) wasn't that great due to concerns about energy costs, hurricane disruptions, and growth in general. Perhaps not surprisingly, then, investors weren't exactly clucking about somewhat cautious guidance from Pilgrim's Pride on Monday.

While the company's fourth-quarter results weren't particularly strong, expectations were pretty modest. Revenue declined less than 1%, but missed the average estimate by a few percentage points. Looking at margins and profits, there are some items in the year-ago period that interfere with straight comparisons. With those items, earnings per share fell by about one penny and the operating margin fell by almost a full percentage point. Excluding items, the operating margin was basically flat, and net income was actually up about 14%.

Looking at straight-as-reported comparisons, total chicken sales were up about 1%, with U.S. sales up less than a half-percent and Mexico sales up almost 8%. Export sales were once again strong (up more than 72%), but still less than 10% of the company's overall revenue.

If the news items right now are any indication, the coming year should have a lot of moving parts. Grain prices are quite low right now, and USDA projections suggest they'll head even lower. But energy, packaging, and transportation costs all remain fairly high.

The larger issue, though, is likely to be the avian flu outbreak. If the outbreak misses the U.S. again, it's quite possible that U.S. exports will be in even higher demand. If the outbreak does hit the U.S., it's anybody's guess what will happen to demand and pricing.

As you might expect from a commodity company, the return on invested capital at Pilgrim's Pride has jumped around over the years. While the industry seems to be getting more rational as a whole, there is still a wide range of uncontrollable factors (grain costs, energy costs, foreign demand, and export supply) impacting earnings. Today's P/E ratio looks pretty enticing, but investors will likely need to be prepared to sit tight on these shares to see real appreciation.

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Fool contributor Stephen Simpson has no financial interest in any stocks mentioned (that means he's neither long nor short the shares).