 Healthy pelicans can usually cope with their lice , but sick birds may carry hundreds of individuals , which hastens their demise . The pouch louse <unk> <unk> , which occurs in the pouch and therefore cannot be removed by preening , is usually not a serious problem , even when present in such numbers that it covers the whole interior of the pouch , but sometimes inflammation and bleeding may harm the host . The brown pelican has a similarly extensive range of parasites . The nematodes <unk> <unk> and C. mexicanum and the trematode Ribeiroia ondatrae have caused illness and mortality in the Puerto Rican population , possibly endangering the pelican on this island . In May 2012 , hundreds of Peruvian pelicans were reported to have perished in Peru from a combination of starvation and roundworm infestation . 
