Little Penguins

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Little Penguins are the smallest of the species of penguin. Growing on average to a height of 33cm and a kilogram, with the males being slightly larger than the female penguins. Found across the Southern coast of Australia and New Zealand, little penguins primarily exist in offshore colonies which protect themselves from invasive predators such as cats.

The little penguins diet primarily consists of small fish, crabs and other crustaceans. It’s not uncommon for a penguin to deep dive for their prey as deep as 60 metres, whilst the average diving time is 21 seconds.

In recent times there has been significant colony decline in many regions in Australia, however the overall population is still listed as not of concern. The primary cause of population decline is believed to be from encroaching human presence in their habitat and fishing in the feeding grounds of little penguins.

Taxonomic classification

ClassAvesbirds
OrderSphenisciformespenguins
Family      Spheniscidaeflightless pelagic seabirds, widely distributed in cooler waters of the southern hemisphere
Genus        Eudyptulaeu well, good dyptes diver
Speciesminorsmaller
Common
Names
 Fairy Penguin, Little Blue Penguin, Northern or Southern Blue Penguin
Little penguin Eudyptula minor

Appearance

LITTLE PENGUINS adapted primarily for swimming and diving underwater differ from other birds in several ways:

  • streamlined bodies that reduce drag while swimming
  • flippers that provide propulsion during swimming are modified wings
  • neutral buoyancy provided by bones that are solid and heavy and a layer of blubber – prevent them from sinking too deep or floating which makes diving easier
  • legs and webbed feet act as a rudder for underwater manoeuvring – short and set far back on the body giving them a waddling gait on land; despite this, they are quite agile on land although walking expends more energy than swimming
  • their feathers have become short and stiff and form a dense cover over the whole body surface which provides effective insulation against the cold
  • oil gland at the base of the tail – during preening, the waxy secretion from this gland is spread through the coat to waterproof it
  • pale fur underneath (thought to be less visible to fish) and darker above
  • sexes are similar but males are heavier and larger than females

Little Penguins

  • smallest of the penguins – only 40cm (16in) tall and 1.1kg (2.4lbs)
  • none of the plumage ornaments of the other species

Distribution

  • southern coastline of Australia from Fremantle, Western Australia to northern New South Wales, mainly on the offshore islands
    also in New Zealand, Chatham Islands
  • largest known colony is on Phillip Island near Melbourne – 20,000 birds
    fledglings disperse widely; longest known movement was from Phillip Island to Spencer Gulf – 1100km (690miles)

Feeding

Prey

  • varies seasonally and from year to year and also depends on the geographical location of the colony
  • small, highly mobile, midwater shoaling fish (anchovy and pilchard) and squid <12cm (5in)
  • also crustaceans
  • food resources are patchily distributed

Foraging

  • foraging is a solitary activity but a number of little penguins may end up at the foraging ground
  • where food resources are patchily distributed and constantly moving (fish), individuals may experience widely varying fortunes in finding food
  • catch prey by pursuit – dive to shallow depths usually < 15m for about 23 seconds
  • the duration of foraging trips and the distances travelled vary according to season:
 Breeding seasonNon-breeding season
Distancewithin 8-15km (5-10 mile) radius from the burrow; a total distance of about 24km (15miles)up to 700km (435miles) but tend to stay within 20km (12.5miles) of shore
Duration12-18 hrsseveral days

Lifestyle

Dependant on both land and sea for their survival

Land

  • come ashore at night – wait for a group to gather before leaving the water and crossing the beach
  • return to land to breed and rear their young, and to moult
  • after their young are independent, they spend 6 weeks at sea to fatten-up before moulting which takes about 3 weeks; during this time the birds are confined to land and can lose up to 50% of their body mass
  • during moulting they remain in the burrow
  • individual birds are not always seen each year

Sea

  • spend the day at sea foraging
  • 80% of their time is spent at sea
  • can and do swim on the surface at speeds of 5-8km/hr (5mph)
  • when travelling long distances, they porpoise – plunge in and out of the water

Mortality

Survival rates

  • less than a third of fledglings (31%) survive to maturity (about 3 years)
  • adult mortality on Phillip Island is about 25% annually – 75% survive to the next year
  • life expectancy for breeding adults = 6.5yrs; oldest known bird was 21yrs

Causes of mortality

  • almost all mortality of first- and second-year birds occurs at sea – most likely causes are starvation and internal parasites
  • adult mortality at sea caused by starvation -it is not known whether due to food shortages or bad weather that makes foraging difficult

“Wreck” of 1986

  • In autumn 1986, 2000 Little Penguins were found dead along tidelines in western Victoria – cause of death was starvation exacerbated by parasites; some of the birds had been banded at Phillip Island less than 6 months previously suggesting that most of these birds were first-year birds
  • It is thought that such concentrated mortalities occur periodically

Predation

On land

  • mainly foxes and dogs
  • interestingly it was found that cats were not a significant predator at Phillip Island
  • lizards and snakes take eggs and hatchlings

At sea

  • sharks and seals

Reproduction

Where

  • breed mainly on offshore islands or along parts of the coast that have reduced access to mammalian predators; the only penguin species to nest on the Australian mainland
  • generally return to their natal colony to breed (like salmon, turtles)from year to year they return to the same location and often the same burrow
  • always breed undercover – in caves, burrows, dense vegetation

When

  • egg laying peaks in August – October
  • reproductively active at 2-3 years of age

Burrow construction

  • length – average of 43cm (17in) long (longest was 100cm (39in))
  • entrance hole – 14cm high x 22 cm wide (5.5 x 8.5 in)
  • excavation may take several weeks and often more than one is constructed
  • the male renovates old burrows or digs new ones

Nesting

  • both male and female build nest
  • lined with plant material
  • egg laying peaks in August – October
  • most clutches have 2 eggs
  • sometimes the pair produces a second clutch in a season
  • a burrow infested with fleas is a good indicator of an active nest!

Chick rearing

  • incubation and chick rearing take around 13 weeks – shared equally by both parents; both parents have a brood patch
  • incubation of the eggs before hatching takes about 5 weeks; the hatchling stage lasts for about 8 weeks
  • chick uses an egg tooth to chip its way out of the egg; usually takes about 24 hours
  • chicks brooded for the first 7-10 days
  • one parent remains with the chicks for 20-30 days (guard stage); parents alternate duties in shifts that can last 10 days
  • usually chicks are fed regurgitated food every night
  • at three weeks of age, the chicks are active and move to the burrow entrance at dusk to wait for their parents returning with food; they gradually continue to venture further out when full-feathered when they join in groups away from the burrow
  • to keep the nest clean, the birds defecate outside the burrow entrance
  • at the end of the hatchling phase, parents abandon their broods to force the young to leave the burrow and the colony
  • crèches are uncommon in burrow colonies but small crèches of 3-6 chicks are seen in cave colonies
  • chicks weigh 36-45gms (1oz) at hatching and fledge at about 800gms (1.8lb)
  • generally both eggs hatch but only one chick survives as the parents are unable to supply sufficient food for both; the stronger, larger hatchling is fed until satisfied and then the other

Effects of Reproduction on the Parents

Body mass

  • females lose more body mass than males – 14% for females compared to 4% for males
  • unsuccessful parents lose more than successful ones
  • survival of parents is not affected by this loss of body mass

Subsequent success

  • number of chicks produced by a pair in one season is a good indicator of the number they will produce in the following year
  • older and more experienced male breeders produce more offspring than younger, less experienced ones; age and experience seems to have no effect on the reproductive success of females

Moulting

  • successful parents moulted sooner after breeding than birds whose attempts failed

Social System

General

  • Little Penguins exhibit a complex repertoire of visual and vocal displays to cover all types of social interactions – greeting, courtship, and aggression
  • most social interactions on land take place at night
  • the birds are very vocal on land at night – they call most frequently after dusk when birds have returned from the sea and before the pre-dawn departure
  • being part of a colony with the resultant social noise results in increased rates of displaying and copulating (this apparently contagious sexual behaviour is seen in many bird species that live in colonies)

Displays

Appeasement Behaviours

  • face away from the dominant bird
  • walk with the head and body held low

Aggressive behaviours

  • direct look
  • zigzag approach
  • contact – bill to bill; bill slapping; breast butt; bill lock twist; lunge peck
  • overt – bite on neck and hit with flipper

Sexual behaviours

  • advertising – performed by unmated males
  • mutual display between pairs where one partner copies the action of the other
  • allopreening where the pair preen each other (known in lots of bird and mammal species)

Copulation behaviour

  • occurs inside or close to the burrow

Status

Phillip Island

  • number of breeding colonies has reduced from ten to one resulting in a reduction in numbers since the turn of the century largely due to habitat loss
  • population size and number of breeding birds have continued to decline (1968-1988)

Other islands

  • no evidence of decreasing numbers in colonies on most offshore islands
  • exceptions are the islands with larger human populations

References

Penguins

  • Emu 91:32-35
  • Emu 91 Part 5 Little Penguin Supplement
  • Fairy Penguins & Earthy People. P Reilly. 1983. Lothian Publishing Company, Melbourne.
  • Penguins. J Sparks & T Soper. 1987. The MacMillan Company of Australia, South Melbourne.
  • The Penguins. TD Williams. 1995. Oxford University Press, Oxford.
  • The Penguins: Ecology and Management. P Dann, I Norman, P Reilly (eds). 1995. Surrey Beatty & Sons, Chipping Norton.

Birds

  • A Natural History of Australia. TM Berra. 1998. University of NSW Press, Sydney.
  • Australia’s Amazing Wildlife. 1985. Bay Books, Kensington.
  • Encyclopedia of Australian Wildlife, Reader’s Digest Australia Pty Ltd, 1997. Reader’s Digest(Australia) Pty Ltd, Surrey Hills.
  • Reader’s Digest Complete Book of Australian Birds. 1982. Reader’s Digest Services, Surrey Hills.
  • What Bird is That? NW Cayley. 1946. Angus & Robertson, Sydney.

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