Pair of male and female penguins in focus with another two playing in the background.

Author: Walter Butler

Title: A History of the Birds of New Zealand.

Chromolithograph of a group of emus.

Author: Alfred Edmund Brehm

Title: Brehms Tierleben

A pair of foxes in the snow.

Author: Alfred Edmund Brehm

Title: Brehms Tierleben

A pair of male and female coots resting in reeds.

Author: Naumann

Title: Naturgeschichte der Vögel Mitteleuropas (Natural History of the Birds of Central Europe)