Bald eagles are making a comeback, but on Saturday in Maryland, 13 of them were found dead. Investigators were called to a farm on the Eastern Shore that day after a man who was searching for antlers shed by deer stumbled upon four of the dead eagles, the Baltimore Sun reports; officers found the other nine on the grounds. Officials aren't saying whether the eagles were purposely killed, though one says there were "no obvious signs of trauma with these birds." The US Fish and Wildlife Service is investigating what the Washington Post notes is "the largest single die-off of bald eagles in the state in 30 years."
Three of the 13 birds were mature, meaning they are "the ones we all love that look like the national bird," a spokesperson for the Maryland Natural Resources Police says—they had white heads and brown bodies. Two were close to maturity, and the rest were immature and did not have any white feathers. A reward of $2,500 is being offered for information that leads to a conviction, the Sun reports, even though it's not yet clear whether a crime was committed. One possibility is that a landowner put out poison to control a rodent problem and the eagles ate poisoned animals, NBC News reports.