Martin Willis / Budgerigar (Melopsittacus undulatus) father with begging chick at nest cavity, Queensland, Australia

Murray Cooper / Spot-breasted Woodpecker (Colaptes punctigula) at nest cavity, South America

Doug Wechsler / Yellow-plumed parakeets (Leptosittaca branickii) at nest cavity in wax palm stump, Tapichalaca Biological Reserve, Ecuador.

Michael Quinton / Northern Flicker (Colaptes auratus) carrying fecal sac from nest cavity in forest, Alaska

Donald M. Jones / Red-breasted Nuthatch (Sitta canadensis) chick in nest cavity, western Montana

Alan Murphy / Northern Flicker (Colaptes auratus) female at nest cavity with chicks, British Columbia, Canada

Alan Murphy / Northern Flicker (Colaptes auratus) male at nest cavity with chicks, British Columbia, Canada

Michael Quinton / Northern Flicker (Colaptes auratus) at nest cavity with chicks, Alaska

Michael Quinton / Northern Flicker (Colaptes auratus) parent at nest cavity with chick, Alaska

Michael Quinton / Northern Flicker (Colaptes auratus) chicks in nest cavity ready to fledge, Alaska

Michael Quinton / Northern Flicker (Colaptes auratus) chicks in nest cavity ready to fledge, Alaska

Michael Quinton / Northern Flicker (Colaptes auratus) chick in nest cavity ready to fledge, Alaska