Little (Blue) Penguin

Distribution:

Populations of Little Penguins can be found at various places along the coasts and surrounding islands of New Zealand and Australia.

Several subspecies are recognized. The White-Flippered subspecies (E. m. albosignata) was until recently regarded as a species in its own right. Other subspecies are the Cook Straight Little Penguin (E. m. variabilis) found on the south coast of New Zealands North island, the Northern Little Penguin (E. m. iredalei) found at the N end of NZ N island, the Australian Little Penguin (E. m. novaehollandiae) found in S Australia and Tasmania, the Southern Little Penguin (E. m. minor) found on the W and SE coast of NZ S island, and the Chatham Little Penguin (E. m. chathamensis) found on Chatham Island, 1000 km E of NZ S island. Based on mitochondrial DNA similarities, the subspecies can now be split into two groups. The first group includes the penguins from Australia (E. m. novaeholandiae) and the most southerly NZ species (E. m. minor). All other subspecies belong to the second (Banks et al., 2002. Notornis 49, p.29-38). Morphological analysis and analysis of sonagrams of penguin braying calls (vocalization) further support this distinction. Interestingly, the 12S ribosomal subunit gene is more diverged between the two groups (clades) of Little penguins, than between Royal and Fiordland penguins. The most likely theory to explain the two groups (according to Banks) is that following climatic cooling that led to extinction of the most southerly New Zealand Little penguins, temperatures rose again and the area became repopulated by migrant penguins from Australia. This is supposed to have happened between about 100 and 200 thousand years ago.

E. m. minor	E. m. albosignata (Note: white leading edge of flipper)

Feeding:

Little penguins primarily feed on small fish, including Pilchard, Australian Anchovy and Sandy Sprat. However, squid and crustaceans will also be eaten if fish supplies are insufficient. Small fish are swallowed head-first under water, whilst the penguin usually surfaces to eat more than 3 cm long ones. Feeding is during daylight when the penguin can see the silvery reflection of light on the fish. Maximum dive depths of over 50 meters have been recorded, yet most hunting takes place in depths of less than 20 meters. A detailed study on diving by birds breeding at Phillip Island, Australia, was performed using depth and acceleration loggers attached to a number of penguins (Ropert-Coudert et al., 2006. Marine Ornothology 34, p.71-74). Of the over 40000 dives performed by the 37 female birds monitored, about 70% were less than 6 meters deep. Median dive depth varied strongly from bird to bird (1.9-20.8 m) and the bird having the highest medium dive depth also performed the deepest dive to 66.7 meters which lasted 90 seconds. The deep dive was at the end of a sequence of 25 above average depth dives. The penguin appears to have accelerated downwards after reaching a depth of 50 meters, suggesting that it spotted prey below that depth. Penguins usually descend with a constant speed until spotting prey (Kato et al., 2006. Marine Ecol. Progress Series 308, p.293-301). Upon ascent, the penguin initially used its flippers to accelerate, probably reflecting some urgency in surfacing due to waning oxygen levels. Usually, Little penguins ascend passively by virtue of their buoyancy (Sato et al., 2002. J. Exp. Biol. 205, p.1189-1197)

Little penguins are considered inshore breeders since most feeding takes place within 25 km of the coast. Daily round trips of 75 km are often recorded. During the winter, penguins may swim further from the colony (distances of 750 km have been recorded, although the penguins tend to stay within 20 km of the coastline). Little penguins propel themselves forwards by flapping their flippers using pectoral and supracoracoideus muscles (abdominal muscles are not involved). Forward thrust is generated both on up- and downstroke (Boggs et al., 2001. J. Exp. Biol. 204, p.3581-3586)

Reproduction:

Little penguins tend to be very faithful to nesting sites. Similarly, pair bonds are strong and are commonly maintained over many seasons. This may be the result of the nearly year-round presence at the colony. Less than 1% of penguins are thought to move to other colonies during their lifetimes. Nesting occurs in underground burrows, usually in soft ground near beaches. Burrows may be dug if necessary using bills and feet. They are usually at least 2 meters apart and burrow entrances are defended vigorously. Nesting under houses or in artificial nest boxes is also common. The latter suffer the disadvantage of elevated temperatures inside when exposed to the sun (Ropert-Coudert et al., 2004. Wildlife Soc. Bull. 32(1), p.177-182), although breeding success appears similar in nesting boxes compared to natural nests (Klomp et al., 1991. Emu 91, p.190-193). Plant materials including grasses and seaweed is used to line nests. Males may occupy a nest first, or find a partner before doing so, depending on the colony. Courtship displays may vary according to nesting conditions. For example, in narrow burrows a classic upward-stretched ecstatic display may not be possible. Copulation also occurs in burrows. Drumming of the males flippers on the female, which generally precedes copulation may be audible outside burrows.

Both burrow and mate fidelity have been statistically analysed at Lion Island, NSWales, Australia (Rogers and Knight, 2006. Ibis 148, p.801-806). Over 75% of both male and female birds return to the same nest in subsequent years. Virtually all other birds moved to nests close by in the same part of the colony. Lower figures have been reported from other sites. Although successful breeders returned to their old nest slightly more often, no statistically significant correlation between previous breeding success and nest fidelity was found. Mate fidelity reached nearly 90% if both partners returned to the colony the next breeding season. However, nearly half of the pairs from the previous season could not reunite since at least one partner did not return to the colony. This was more common in birds that had experienced breeding failure, possibly as these birds were weaker and thus more likely to die or arrive late or not at all at the breeding site. Interestingly, whilst successful breeders were more likely to both arrive back at the colony, their divorce rate is slightly higher than that of unsuccessful breeders that both managed to return. It is possible that this reflects early arrival at the colony of many of these birds and unwillingness to wait for the old mate.

The main breeding season usually commences around september in New Zealand, although when food is plentiful eggs may be laid from May to February, with two pairs of chicks being raised in some cases. At other sites, different times may be preferred depending on local climatic influences. Egg laying is not strongly synchronized between individuals in a colony. After the two eggs have been laid, one parent must incubate whilst the other forages. Little penguins usually perform single day foraging trips, with longer trips becoming more common during the incubation period as parents alternate with incubation duties. When food is scarce, these trips may last for a week. However, long trips may precipitate egg desertion by the incubating bird (Numata et al., 2000. NZ J. Zool. 27, p.277-289). Based on studies with King penguins, it has been suggested that when a critically low level of body fat and/or protein reserves is reached in the incubating penguin, the nest will be deserted so that it can go to sea and feed (Olsson 1997. J. Avian Biol. 28, p.264-267). Hence, both duration of partner absence and body condition play a role in desertion. A probably hormonally triggered decrease in foraging trip lengths has been noted towards the end of the incubation period, ensuring that the chicks can be fed reasonably soon after hatching. The incubating parent is unlikely to have enough food left in its stomach to feed the chicks, since meals are usually digested within 16 hours (Gales 1987. Ibis 129, p.335-343). Chicks tend to starve if not fed within 3 days of hatching.

Eggs usually hatch within 1-3 days of each other after an incubation period of about 37 days. After hatching, parents continue to alternate in guarding the chicks (Guard Period). A mostly daily alternation of nest attendance can be observed during this period. Guarding is necessary until chicks can thermoregulate themselves, and also serves to protect against predators. Guard Periods ranging from 10-28 days were observed in comparative studies of two colonies in Numata et al., 2004 (NZ J. Zool. 27, p.277-289). Penguins in colonies where food is scarce appear to brood chicks for less long (due to the need for both parents to forage), and similarly when 2 chicks are being raised, brooding is shorter than when only a single chick is being raised (since both parents need to forage sooner to feed the additional chick). When food is scarce the chicks may be abandoned, resulting in starvation. For example, a third of chicks were abandoned on Motuara Island (NZ) in the 1998/99 breeding season when pilchard levels were below average. Parents may preferentially feed a single chick, resulting in death of the other. This form of brood reduction strategy may ensure survival of at least one chick. After the Guard Period, chicks stay alone in nests and may come to the entrance (if nesting in burrows) at dusk to await the adults. Creching is unusual but may occur when birds live together in large caves. After about 8 weeks fledglings may go to sea. The body mass at fledging correlates with survival in the first year (Dann 1988. Emu 88:101-103). Young birds may stay far from the colony until reaching sexual maturity at an age of 2-3 years when they usually return.

The ability to raise two pairs of chicks in one breeding season makes the little penguin unique among penguins. Birds laying two clutches raised 1.7 times as many chicks as single clutch parents, with fledging chicks having equal chances of survival as those from single clutches. Birds are more likely to lay two clutches as they get older, and it also appears that these birds have above average survival rates, above average breeding rates in subsequent seasons and the increased propensity to raise 2 clutches again in subsequent seasons (Johannesen et al., 2003. J. Avian Biol. 34(2), p.198-210).

Little penguin chick in nest burrow, Otago Peninsula, NZ	Little penguins in front of nest burrow, Otago Peninsula, NZ

General Behaviour:

Little penguins are nocturnal animals on land and are unique among penguins in this respect. Penguins leave and return to their colonies under cover of darkness. Whilst individuals may be spotted during daylight (for example White-Flippered Little Penguins on Banks Peninsula) this is unusual and involves small numbers of birds in areas not subject to much disturbance. In the evening, birds tend to assemble offshore in groups until light levels are low enough for them to head onto land. This results in large batches of birds arriving nearly simultaneously.

Little penguins are regarded as quite aggressive. Two main aggressive stances can be observed; (i) body held low with beak pointing at the adversary and flippers raised above body, (ii) body upright, feathers on head erect and flippers outstretched. In both cases the penguin can growl or bray to emphasize the stance. If fighting occurs, both birds may sustain significant injuries to the face and eyes.

On the other hand, Little penguins may be observed allopreening each other. This behaviour is not only limited to partners.

Threats:

The main threat to colonies of little penguins are introduced mammalian predators. Foxes, dogs, cats, ferrets and stoats may kill birds at their colonies. Foxes and dogs are particularly problematic since they may kill up to 50 birds in a single night, in worst cases leading to complete loss of the colony. Natural predators include sharks, fur seals, gulls and eagles.

Human development is also a problem as many penguins are killed on coastal roads, nesting sites may be developed or trampled on by humans or livestock and penguins may become entangled in or ingest rubbish. Further, dog attacks are most common near human settlements. Nesting sites can be damaged by fire or overgrazing by livestock or rabbits, which removes the protective vegetation and increases problems with erosion or flooding at the nesting site. On the other hand, certain types of vegetation can prove difficult for penguins to penetrate such as the introduced Kikuyu grass. Fisheries may be a problem, particularly in times of food shortages.

At sea, oil is a particular problem. When a large volume of bunker fuel oil spilled along the north coast of Tasmania following the havarage of the "Iron Baron" at Low Head in July 1995, it is estimated that between 8 and 18 thousand penguins died at sea. 1894 penguins were captured and deoiled. In order to avoid lengthy captivity (which may be associated with stress and disease), these birds were released further south. An initial batch was released 360 km from their capture site and several birds had transmitters attached to monitor their positions. Within 3 days, 2 birds had already returned to the capture site. Since the clean-up was still in progress, further releases were made even further south to delay the birds return. Within 4 months, 56% of relocated penguins had returned to Low Head. After returning, these birds showed similar survival rates to those of unoiled control birds (Hull et al., 1998. Biol. Conservation 86, p.393-400).

Little penguins are afflicted by a number of parasites including fleas, lice and ticks. Mosquitos and midges may also bite the penguins. Whilst these insects are not particularly debilitating, they may be involved in viral transmission. Viral infections may be subclinical, but certain tick-borne flaviviruses have been shown to be potentially lethal to little penguins (Morgan et al., 1985. J. Wildlife Dis. 21(3), p.193-198). The effect of viral infection is likely to be more significant when Penguins are already weakened by other factors.

Studies on Penguin Island (W. Australia) showed a clear trend of lower nest-box usage in areas subject to most (uncontrolled) human disturbance, and additionally lower hatching and fledging levels from birds making use of these boxes (Klomp et al., 1991. Emu 91, p.190-193). Properly controlled tourism does however not appear to be a major threat to colonies. A very detailed explanation of threats facing little penguins is found on http://www.penguins.cl/little-penguins.html.

Where To See:

There are a variety of sites in both NZ and Australia where it is possible to view Little penguins under proper supervision. For example, the White-flippered subspecies can be seen on Banks peninsula. The Southern Little penguin can be viewed at the Oamaru penguin colony or at Pilots Beach on Otago Peninsula, both on the east coast of NZ South Island. The Australian Little penguin can be viewed on Phillip island in SE Australia (under floodlights).

Little penguins rarely venture onto land before dark and are scared by bright lights such as torches and especially camera flashes. I have seen a group of penguins flee back into the sea in response to a camera flash at least 20 meters away. It is important to avoid this, especially when there are hungry chicks waiting at the nests. Hence, please keep lights dimmed or use red lights and avoid photographing birds returning to nests (this is why I can only offer few photos of these penguins).