If ever one needed an excuse to post pictures of penguins, yesterday was World Penguin Day.

King penguins at Green Gorge

King penguins are much more graceful in the water than on land!

Four penguin species breed on Macquarie Island. King penguins (Aptenodytes patagonicus) can reach a metre tall and can dive to deeper than 300 metres. Royal penguins (Eudyptes schlegeli) are endemic to Macquarie Island, where they breed in colonies up to 1 km from the coast. Rockhoppers (Eudyptes chrysocome) and gentoos (Pygoscelis papua) breed in smaller numbers.

Royal penguins at Finch Creek.

What do penguins have to do with plants? Plants require nitrogen and penguins produce lots of nitrogen. Although nitrogen is an essential plant nutrient too much of it can be toxic to plants. Nitrophilous plants are well adapted to abundant nitrogen. On Macquarie Island the herbs Callitriche antarctica and Montia fontana and the grasses Poa annua and Poa cookii are frequently found in and around penguin rookeries and seal wallows where nitrogen concentrations are high. Studies on subantarctic Marion Island show that plant nutrients are derived mostly from the ocean, as aerosols and as excreta from seabirds and seals. Plants growing around penguin rookeries tend to have high concentrations of nitrogen and a characteristic bright green leaf colour. Animal-derived nitrogen is a key nutrient source for plants in the subantarctic, where nitrogen from other sources such as bedrock and nitrogen-fixing cyanobacteria is limited.

Gentoo penguin.

Macquarie Island’s penguin populations are still recovering from exploitation in the early 1900s when an estimated 150,000 penguins were slaughtered for oil every year. Many penguin species are listed as threatened on the IUCN Red List. A recent review of threats to penguin populations points to the need for an effective global network of marine reserves.

Penguin digestors at the Nuggets. Thousands of penguins were boiled alive in these to produce oil in the late 1800s and early 1900s. High-rise royal penguin colony in the background.

Penguin city. The population of king penguins at Lusitania Bay is at least 350,000 and growing.