Feather pecking (FP) is a major problem in cage and free-range housing systems.In free-range systems, FP is more difficult to control. It is not known why avictim is being pecked. It could be that a bird is genetically predisposed to bepecked. To study the genetics of FP behavior, a large F2 population of 630 henswas generated from a cross between two commercial laying lines differing intheir propensity to feather peck. The traits measured at 6 and 30 wk of age werereceiving gentle FP, receiving severe FP, and receiving aggressive pecking. Inaddition, receiving toe pecking (TP) was also measured at 30 wk of age. Forreceiving gentle FP at 6 wk of age, a significant QTL on GGA1 and threedifferent suggestive QTL were identified on GGA2, GGA6, and GGA7, respectively.For receiving gentle FP at 30 wk of age, a suggestive QTL on GGA5 was detected.For receiving aggressive pecking, a suggestive QTL was detected on GGA3. Forreceiving TP, three suggestive QTL were detected on GGA1, GGA5, and GGA23,respectively. The different QTL detected for receiving gentle FP at differentages indicate that this trait is regulated by different genes in young and adulthens.