McDonald's has another super month ... and Starbucks?

McDonald's (NYSE: MCD) same-store sales were up 8.4% in June. Sales for all stores rose 12.5%.

The company's shares stay near multi-year highs as each month seems to be a bit better than the last.

One of the odd things about McDonald's monthly announcements is that they are rarely viewed without an eye on Starbucks (NASDAQ: SBUX). The market now assumes that because the larger chain says that breakfast and coffee sales are part of its success, that these sales come at the expense of Starbucks.

However, McDonald's could be taking morning food and coffee sales from other fast food establishments. If so, the damage to Starbucks could be insignificant.

But, with Starbucks share traded near 52-week lows, it has become a company that is viewed through the lens of McDonald's performance. Starbucks shareholders will have to wait for it to announce its quarter to get a picture of whether the company's growth has been compromised. If it has been, McDonald's will almost certainly be the culprit and Starbucks may have to settle in for a long siege.

Douglas A. McIntyre is a partner at 24/7 Wall St.