Martin Willis / Victoria's Riflebird (Ptiloris victoriae) male in courtship display, Atherton Tableland, Queensland, Australia. Sequence 2 of 3

Marie Read / Canada geese (Branta canadensis) two during territorial fight in early spring, Ithaca. New York, USA

Donald M. Jones / Yellow-headed Blackbird (Xanthocephalus xanthocephalus) male calling, Montana

Donald M. Jones / Western Meadowlark (Sturnella neglecta) male calling, Montana

Donald M. Jones / Elk (Cervus elaphus) bull bugling, Alberta, Canada

Tomasz Zawadzki/ BIA / Blue-headed Wagtail (Motacilla flava) calling, Poland

Tomasz Zawadzki/ BIA / Great Reed-Warbler (Acrocephalus arundinaceus) calling, Poland

Glenn Bartley/ BIA / Chestnut-bellied Cuckoo (Hyetornis pluvialis) calling, Jamaica

Glenn Bartley/ BIA / Patagonian Sierra-Finch (Phrygilus patagonicus) male calling, Andes, Chile

Scott Leslie / Black-and-white Warbler (Mniotilta varia) male calling in spring, Maine

Alan Murphy/ BIA / Great Kiskadee (Pitangus sulphuratus) and Green Jay (Cyanocorax yncas) fighting, Texas

Donald M. Jones / Elk (Cervus elaphus) bull bugling, western Canada