ALEXANDRIA, Va.—Crispy chicken sandwiches have become so popular that many restaurant chains are on the lookout for relatively rare bird: the small chicken. 

Restaurants such as KFC and Chick-fil-A have come to value chickens that weigh about four pounds, a slimmer bird than the big-breasted varieties most common in the U.S. poultry industry, according to The Wall Street Journal.  

The Journal reports some fast-food executives say the smaller-size birds, which are often used to make sandwiches and chicken-on-the bone offerings, are more tender and flavorful than bigger birds. Chick-fil-A, the biggest U.S. chicken chain by sales, has continuously used small birds for its sandwiches. But the rising demand from restaurants and convenience stores—coupled with chicken companies’ longtime focus on the more profitable big birds—is driving up costs for restaurant operators. 

“What happened was the chicken sandwich … it just became much tougher for us to find that small bird,” said Dan Shapiro, chief executive of Krispy Krunchy Foods, which sells small bird products at roughly 2,700 convenience stores and some stadium concession stands.

KFC, the second-biggest U.S. chicken chain by sales, told its U.S. franchise owners earlier this year that it expected prices for fresh chicken on the bone to drive cost increases this year. One problem contributing to the supply imbalance is that poultry producers are converting plants to handle larger-size birds.

Tom Elam, president of FarmEcon LLC, an agricultural consulting firm, told the Journal that the costs to produce a four-pound bird and an eight-pound bird are similar, but when chicken prices go up, the larger, meatier bird is more lucrative for processors. Chicken processors shifted toward producing larger birds years ago, tightening the supply of the smaller four-pound chicken, executives said. Small chickens were nearly 30% of the market in 2005 but are now about 15%, according to U.S. Agriculture Department data.

The short supply of small chickens has increased competition, and prices, for the available supply, restaurant operators said.

While Krispy Krunchy hasn’t had shortages yet, Shapiro said he was concerned that in a few years the large fast-food chicken chains will monopolize the tight supply of small birds. He said the company is exploring different alternatives.

“We’ll have to see what things look like as we go into 2024,” he said.