Konrad Wothe / Blue Tit (Cyanistes caeruleus) parent collecting fecal sac in nest box, Bavaria, Germany

Tom Vezo / Northern Cardinal (Cardinalis cardinalis) female removing fecal sac from nest near chicks, Green Valley, Arizona

Donald M. Jones / Red-shafted Flicker (Colaptes cafer) male cleaning fecal sac out of nest cavity, Troy, Montana

Donald M. Jones / Northern Flicker (Colaptes auratus) female coming out of nesting cavity with fecal sac, western Montana

Donald M. Jones / Western Bluebird (Sialia mexicana) female exiting nest cavity with fecal sac, western Montana

Donald M. Jones / Northern Flicker (Colaptes auratus) male coming out of nest cavity with fecal sac, western Montana

Tom Vezo / Greater Roadrunner (Geococcyx californianus) parent removing chicks' fecal sac from nest among cactus, Green Valley, Arizona

Jose B. Ruiz / Grey wagtail removing fecal sac from nest {Motacilla cinerea} Spain

Martin Willis / Fernwren (Oreoscopus gutturalis) carrying fecal sac from nest, Julatten, Australia