A federal judge issued an arrest warrant Monday for a Montana man who failed to show up for an initial court appearance on charges of killing thousands of birds, including bald and golden eagles. A second defendant pleaded not guilty.

The two men, working with others, killed about 3,600 birds on Montana’s Flathead Indian Reservation and elsewhere over a six-year period beginning in 2015, according to a grand jury indictment unsealed last month. The defendants also were accused of selling eagle parts on a black market that has been a long-running problem for U.S. wildlife officials.