The write up under 'Fairy Penguin' is very good for an overview of little penguins, but in this node I go into more detail.
There were once two species of penguin recognized under the genus ‘Eudyptula’, the Little Penguin (Eudyptula minor) and the
Fairy Penguin (Eudyptula undina). Now, they are both known as Eudyptula minor in biological literature because it is more accurate, the
Greek word Eudyptula meaning ‘good little diver’. The little penguin is the smallest penguin in the world.
Distribution
Little Penguins are found only in Australia and sub-species being found in New Zealand. They once ranged from Swan River in Western Australia, to Tasmania and up to Moreton bay in Queensland. Now these little penguins are most common along the islands off the coast of Victoria, South Australia, Tasmania and even as far as Freemantle in Western Australia. The only mainland whole breeding colony is at Manly beach (NSW) where approximately 60 breeding pairs live. Tasmania estimates a range of 110 000–190 000 breeding pairs live there, with less than 5% actually living on mainland Tasmania. On Penguin Island, off Western Australia, live about 500 breeding pairs.
Habitat
Little penguins normally live in burrows in sand dunes, rock piles or sea caves. These burrows are dug with their feet, but if the surface is too hard, they will nest on the ground, under vegetation. This also occurs if there are hot, dry summers, and mild wet winters, like the penguins on Penguin Island experience. Throughout the breeding season nesting material is added, made up of any local plant materials. They live in loosely packed colonies, as they are not as social as the Antarctic penguins. These nests are usually at least 2 metres apart and have a 60-80 cm long tunnel with a ‘bowl’ at the end for the nest.
Ecology
Adult penguins weigh about one kilogram, and have a height of 30-40 cm, and on average live to 6 years.
Throughout July and August, male penguins return to their colonies to either dig new burrows or to renovate old burrows and attract females with their noisy courting displays, which consist of a distinctive song, accompanied by flipper, beak and body movements. One mate will be chosen, but they will not usually stay with the partner for life. Among penguins, species at higher latitudes have a faster growth rate which results in a shorter chick rearing period.
In a very good year for food, the eggs may be laid in May until October. The males and females share the incubation duties, in shifts of 1-2 days, which spans from 33 to 37 days, and usually have a clutch of 2 eggs each being 5% of the body weight of the adult, of which 60% successfully hatch. Little penguins differ from all other penguins in that they are double-brooders, meaning that they can rear two consecutive clutches a year.
When the chicks are 5 weeks old, they will stay outside of the burrows, waiting to be fed by both parents. Then, within another 2-3 weeks they are then ready to leave to mature at sea. They are not seen again for a year, and then return to moult. They repeat this pattern each year, for 3 or 4 years, until they are ready to breed.
In about February, at the end of the breeding season, adult penguins build up their fat stores and begin to moult. During this time it is thought that the penguins lose 50 grams a day due to the moulting and at the same time must remain ashore in these 2-3 weeks, so as to give them time for their feathers to become waterproof.
There are two typical traveling patterns for the little penguin, long-term and short-term, which have been explored using radio-tracking. During the breeding season, the short-term trips take place; they last one day and are localized. The penguins will travel to 7.9 kms, and 95% stay within 9km of the shore. Whereas long-term trips occur over the non-breeding season, last several days, and extend to hundreds of kilometers, and 74% of the penguins staying within 20kms of the shore. Some fairy penguins return consistently to their burrows year round but most stay at sea throughout the autumn-winter period. Most of the penguins return to their colonies within an hour or so of darkness.
Diet
Little penguins experience marked seasonal and annual changes in their food supplies.
They usually forage in shallow waters, frequently between the 10–30 m range, not exceeding 60 metres, and mainly feed on schooling fish like anchovies (Engraulis australis), pilchards (Sardinops neopilchardus), squid and krill (Euphausids). The prey is swallowed whole. It is thought that an abundance of pilchards in their diet causes early onset of egg laying. Therefore, the massive death of pilchards in Australia in March to May of 1995 may have affected penguin populations adversely. Only in the last half of 1995 were significant decreases in the penguin population on Phillip Island reported, 1926 penguins were found dead.
At this same time, in Western and South Australia, more than 2000 penguins had died of starvation. In little penguins, starvation can occur when there is a reduction or absence of a food supply, or that combined with bad weather. This type of mortality rate had mostly occurred with the younger penguins, but in the case the deaths were primarily of the adults. During this time, pilchard numbers were low, due to a viral infection that was thought to have been transmitted by migrating fish. It is still not known to what extent the pilchard numbers had to do with the penguin’s mortality rates, because data for the pilchard numbers was only collected once it was realized there was a problem with the penguin population. pilchards and anchoviescomprise 50% of the little penguin’s diet. Little penguins do not tend to eat fish that have an infection, and other species of birds that ate the pilchards were not affected to the same extent that the little penguin was. So it is still unsolved.
An abundance of pilchards and anchovies causes penguins breeding season to occur early, and therefore a higher birth rate. This abundance of pilchards in a penguin’s diet appeared in early studies of 1979, but since then the pilchards have decreased in number. The cause is unknown, but thought to be the due to the commercial fishing.
This study was to show that if the penguin’s diet changed, since the pilchard population was down by 10%, that the penguins would suffer as a result. The end results showed that the penguins were able to breed successfully, but there was limited data to prove anything. This is still being researched.
Studies have been done to compare the percentage of prey items found in stomach contents of little penguins in three studies at Phillip Island when supplies of pilchard were low. It showed that the penguins are able to survive when their main source of food is lowered. All the information suggests that all the penguins need is an abundance of suitably sized fish, not necessarily a certain species.
Size
Adult little penguins differ in size depending on their environment and food availability. In body mass they may differ up to 35%, and in beak length up to 11%.
Little penguins not only have the highest surface area to volume ratio among penguins, but also a flipper surface about 10% larger than they really need. The penguin’s beak growth is also relatively slow, because the beaks do not need to be large until they are to find food for themselves.
In past years the most detailed studies done on the seasonal variation of the little penguins prey has not been examined over years, rather just the single season. But in 2000 an experiment was conducted over 3 years, with one of the years when the supply of food was limited. In this experiment they observed that one penguin from the usual clutch of 2 eggs, are fed first, and because it hatches first, the younger sibling may starve are food is scarce. This happens so that complete breeding failure will not occur. The differences between the first and second hatched was explored, and if they would grow at different rates. Lastly, there was research done on Penguin Island, Western Australia, to see whether the hatchings in different times of the season would have an impact on the penguin’s growth. The results of this experiment showed that the second-hatched chicks generally had slower growing rates and were slightly smaller than their siblings in 3 years time.
Threats
There are different threats for the different populations of penguins around Australia. For the population in Manly it is the destruction of their habitat, like vegetation burn off and predation from foxes, dogs and cats. Humans’ living so close to the penguins also causes damage, deterring penguins from nesting in certain areas near light, noise and movement, as well as delaying the penguins from feeding their chicks on time. Some penguins are drowned, by fishermen setting up nets near a penguin colony, plastics being swallowed, oil spills are a problem for all sea birds- being toxic when ingested, and affecting the buoyancy and insulation of their plumage. Often these penguins are rescued from these sites, and the success of rehabilitation depends solely on the amount of penguins released back into the wild. This means that the penguin’s success in the wild is not monitored, with the most effort going into the collecting and rehabilitation of penguins, and not enough research into their survival later on once they're released.
In the Iron Baron spill of 1995, 1894 penguins were rescued from Tasmania from the biggest on shore oil spill in Australia’s history. When this spill occurred, the penguins that were caught and rehabilitated were banded and had records kept, giving people the chance to monitor the penguin’s survival. The results showed that the penguins had a relatively high survival rate compared to other seabirds. On the different islands that were affected from 44-59% lived.
Sources:
www.publish.csiro.au/journals/mfr
www.publish.csiro.au/journals/emu
www.nationalparks.nsw.gov.au/PDFs/TSprofile_Little_penguins_ManlyCove_pop.pdf
www.publish.csiro.au/journals/wr
www.parks.tas.gov.au/wildlife/birds/penguin.html