Sofia Zoo marmoset, and macaques. The predator sector houses big cats, bears and small predators, including lions, tigers, leopards, pumas and brown bears. In January 2011 the zoo received eight Humboldt penguins on loan from Germany. The penguins are on loan for about 18 months, after which they will be returned, with any offspring to stay at the zoo. The zoo has some 1,400 individual birds representing 192 species. Waterbirds are housed in a lake, and Imperial eagles, Griffon vultures, Egyptian vultures and buzzards in a large walk-through aviary. Other species of birds at the zoo include ostriches, Silver pheasants, peacocks, flamingos,
Hip replacement heat-treated alloys and a lack of special surgical experience accounting for most of the failures. In 2010, surgeons at medical centers such as the Mayo Clinic reported reducing their use of metal-on-metal implants by 80 percent over the previous year in favor of those made from other materials, like combinations of metal and plastic. The cause of these failures remain controversial, and may include both design factors, technique factors, and factors related to patient immune responses (allergy type reactions). In the United Kingdom the Medicines and Healthcare Products Regulatory Agency commenced an annual monitoring regime for metal-on-metal hip replacement patients