<i>Parvalbumin</i> (<i>PV</i>) mRNA staining with radioactive in situ hybridization across species (Anna’s hummingbird, <i>Calypte anna</i>; Downy woodpecker, <i>Dryobates pubescens</i>; Harris hawk, <i>Parabuteo unicinctus</i>; American flamingo, <i>Phoenicopterus ruber</i>; Red-rested turaco, <i>Tauraco erythrolophus</i>; Domestic duck, <i>Anas platyrhynchos domesticus</i>; Emu, <i>Dromaius novaehollandiae</i>; Humbolt penguin, <i>Spheniscus humboldti</i>).

PV expression present in a brain area is denoted by a plus (+) sign; PV absent in a brain area is denoted by a minus (–) sign. (DOCX)