Animal Diversity Web

Ge­o­graphic Range

Py­goscelis papua, or more com­monly known as gen­too pen­guins, are ex­clu­sively found in the South­ern Hemi­sphere be­tween 45 and 65 de­grees south lat­i­tude. Within this range, gen­toos are found on the Antarc­tic Penin­sula as well as many sub-Antarc­tic is­lands. Only about 13% of all gen­too pen­guins live south of the Antarc­tic ice pack.

One of the most pre­dom­i­nant lo­ca­tions gen­toos in­habit is the Falk­land Is­lands in the South At­lantic Ocean. Around 40% of P. papua world­wide are found within this arch­i­pel­ago. (Pis­to­rius, et al., 2010; Quin­tana, 2001)

• Biogeographic Regions
• antarctica
  • native

Habi­tat

Gen­too pen­guins typ­i­cally are found along the shore­line. This al­lows the pen­guins to be able to quickly ac­cess food while re­main­ing close to their nest. They pre­fer el­e­va­tions close to 115 me­ters above sea level along the shore be­cause the snow in these areas tends to melt first. The higher the al­ti­tude, the de­creased like­li­hood of nest-flood­ing as the snow starts to melt dur­ing the sum­mer. The ter­rain in these areas is also flat which helps to sta­bi­lize their nests. Gen­too pen­guins pre­fer north-fac­ing lo­ca­tions for nest­ing, which is thought to be linked to ab­sorb­ing solar ra­di­a­tion. The main fea­ture of gen­too habi­tats is the preva­lence of small peb­bles, typ­i­cally under 5 cen­time­ters in di­am­e­ter. These peb­bles are the main build­ing blocks in cre­at­ing a suf­fi­cient nest to hold the eggs dur­ing breed­ing sea­son.

Gen­too pen­guins also spend some of their day un­der­wa­ter for feed­ing ex­cur­sions. These aquatic trips are typ­i­cally short; the longest dive on record is only two min­utes long. Gen­toos typ­i­cally dive down only 3 to 20 me­ters, with oc­ca­sional deeper dives up to 70 me­ters. (Adams and Brown, 1983; Quin­tana, 2001)

• Habitat Regions
• polar
• terrestrial
• saltwater or marine

• Terrestrial Biomes
• tundra
• icecap

• Aquatic Biomes
• coastal

• Average elevation

  115 m

  377.30 ft

• Range depth

  3.5 to 70.0 m

  11.48 to 229.66 ft

• Average depth

  9.0 m

  29.53 ft

Phys­i­cal De­scrip­tion

Like all pen­guin species, the ven­tral side of gen­too pen­guins is white while the dor­sal side is black. This color pat­tern is known as coun­ter­shad­ing. This adap­ta­tion is use­ful while swim­ming un­der­wa­ter; the lightly col­ored ven­tral side helps pen­guins blend in with the sky for preda­tors or prey that are look­ing up. The dark dor­sal side blends in with the ocean floor for preda­tors or prey look­ing down.

The major dif­fer­ence be­tween gen­too pen­guins and other pen­guin species are their head mark­ings. Gen­toos fea­ture two white wedges around their eyes that are con­nected by a medium-sized line across the tops of their heads. Their heads are mostly cov­ered in black feath­ers but small flecks of white feath­ers can also be found.

The feath­ers of gen­toos are very fine; every square inch of their body can be cov­ered with up to 70 feath­ers. Gen­toos are part of a group called the "brush-tail pen­guins" which char­ac­ter­izes their tails as hav­ing longer feath­ers than those of other pen­guin species. Their tails con­sist of 14 to 18 feath­ers and are about 15 cen­time­ters long. Be­cause gen­toos are aquatic, they must make their feath­ers wa­ter­proof. Using their bills, they do so by cov­er­ing their feath­ers with oil found in the uropy­gial gland near the base of their tails.

Of the 17 pen­guin species, gen­too pen­guins are the third largest in size. They stand roughly at 76 cen­time­ters when they reach adult­hood. De­pend­ing on the time of the year, they can weigh any­where from 4.5 to 8.5 kilo­grams. Heav­ier weights are seen dur­ing their month-long molt­ing phase.

Their feet are stout, fat, and webbed. They are bright or­ange with long black claws ex­tend­ing from the web­bing. The beak of a gen­too is par­tially black but has a bright dark-or­ange to red spot on ei­ther side. The color of the spot is at­trib­uted to the carotenoids ab­sorbed from the krill they eat.

There is very lit­tle dif­fer­ence be­tween the males and fe­males. The main char­ac­ter­is­tic dif­fer­en­ti­at­ing be­tween the sexes is size. Males are sig­nif­i­cantly larger than fe­males in al­most all re­spects such as bill length, flip­per length, and height.

Gen­too pen­guins look very sim­i­lar from the time they hatch until their first molt which oc­curs at around 14 months. Chicks have downy-gray feath­ers and a weak, dull-col­ored bill. The white wedges around the eyes are no­tice­able at a young age; how­ever, they are not as well-de­fined or con­nected along the top of their head like the adults. (Cuervo, et al., 2009; McMil­lan, 1993; Naveen, 1999; Ren­ner, et al., 1998; Williams, 1995)

• Other Physical Features
• endothermic
• heterothermic
• bilateral symmetry

• Sexual Dimorphism
• sexes alike
• male larger

• Range mass

  4.5 to 8.5 kg

  9.91 to 18.72 lb

• Range length

  70 to 95 cm

  27.56 to 37.40 in

• Average length

  75 cm

  29.53 in

• Range wingspan

  22.2 to 25.6 cm

  8.74 to 10.08 in

Re­pro­duc­tion

Fe­males' choice of male mates is based on male be­hav­iors. First, the male gen­toos find the best spot for a po­ten­tial nest. The prime areas are those that are flat with lit­tle to no snow or ice. Once a po­ten­tial nest site is cho­sen, the males point their bills ver­ti­cally in the air and bel­low out calls. The calls an­nounce to the fe­males to come and in­ves­ti­gate their nest site. If a fe­male wad­dles by and "likes" the nest site, the male and fe­male will mu­tu­ally dis­play by trum­pet­ing or bow­ing.

Gen­too pen­guins are monog­a­mous dur­ing a breed­ing sea­son, with some pair bonds last­ing a life­time. "Di­vorces" (the break­ing of pair-bonds) do occur be­tween breed­ing sea­sons. In this case, fe­males choose a new part­ner that has dis­played greater re­pro­duc­tive suc­cess. As colo­nial breed­ers, di­rect ob­ser­va­tion of nest­ing suc­cess is pos­si­ble. The di­vorce rate in gen­toos is less than 20 per­cent, which is rel­a­tively low com­pared to other pen­guin species. The ben­e­fit to a monog­a­mous re­la­tion­ship is that mates do not have to ex­pend time and en­ergy find­ing new mates each year. (Crox­all and Davis, 1999; Frédérique, et al., 1998; Williams, 1995)

• Mating System
• monogamous

Gen­too pen­guins can begin breed­ing at two years of age, al­though most don't until they are about three or four. Liv­ing in colonies, gen­too pen­guins can gather in groups of over 2,000 pairs at one breed­ing site. At the be­gin­ning of the breed­ing sea­son, nests are built by the par­ents. Gen­too nests are spaced about a meter apart. The egg-lay­ing sea­son for P. papau be­gins from June to mid-Au­gust and usu­ally fin­ishes in late Oc­to­ber to late No­vem­ber.

After the nest has been com­pleted, the fe­male will stay at the nest and lay her egg 5 days post-breed­ing. A sec­ond egg is laid three days later. The eggs are spher­i­cal and green­ish-white. The weight of the first egg in re­la­tion to the sec­ond egg varies be­tween nest­ing lo­ca­tions, but on av­er­age egg weight is 125 grams. There have been rare cases where one or three eggs were laid.

If the set of eggs is lost, gen­too pen­guins can lay a sec­ond set of eggs dur­ing the same breed­ing sea­son. These eggs are laid near the end of the breed­ing sea­son when the fe­male re­gains suf­fi­cient en­ergy. The down­side to a late lay­ing is re­duced en­ergy, caus­ing a late molt­ing pe­riod. Fe­males do not have enough en­ergy to begin their molt right after breed­ing and there­fore delay molt­ing. This, in turn, de­lays egg-lay­ing the fol­low­ing year. In­deed, the fe­male may not have enough en­ergy to lay a clutch the next year.

The eggs are in­cu­bated for an av­er­age of 35 days be­fore hatch­ing. Al­though the eggs are laid days apart from each other, they typ­i­cally hatch on the same day or one day apart. The chicks are frail and weigh about 96 grams. The chicks stay at the nest for the first 75 days until they are ready to fledge and visit the ocean for the first time. Dur­ing this fledg­ing pe­riod, gen­too chicks make an av­er­age of 5 trips to sea. The young reach in­de­pen­dence 20 days post-fledg­ing. (Bost and Jou­ventin, 1990; McMil­lan, 1993; Williams, 1995)

• Key Reproductive Features
• iteroparous
• seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• oviparous

• Breeding interval

  Gentoo penguins breed once a year.

• Breeding season

  The breeding season for gentoo penguins starts in June to mid-August and ends in late October to late November.

• Range eggs per season

  1 to 3

• Range time to hatching

  34 to 35 days

• Average time to hatching

  37 days

• Range fledging age

  75 to 105 days

• Average fledging age

  80 days

• Range time to independence

  85 to 105 days

• Average time to independence

  100 days

• Range age at sexual or reproductive maturity (female)

  2 to 3 years

• Average age at sexual or reproductive maturity (female)

  2 years

• Range age at sexual or reproductive maturity (male)

  2 to 3 years

• Average age at sexual or reproductive maturity (male)

  2 years

Both par­ents are in­volved in nest-build­ing. The nest is bowl shaped with a wide edge and a hol­low cen­ter. Nest size ranges be­tween 10 to 20 cm in height and around 45 cm in di­am­e­ter. Nests are made from small stones found around the nest­ing site, in­clud­ing stones stolen from other nests. Medium-sized nests can con­tain over 1,700 peb­bles. Al­though peb­bles are the main com­po­nent of nests, some­times molted feath­ers, twigs, and veg­e­ta­tion are used.

Mem­bers of both sexes de­fend their nests from other birds that come too close. P. papau will stick out its bill to­ward the in­vader and let out a low hiss. Com­pe­ti­tion for ter­ri­tory ex­ists be­tween two ad­ja­cent nests in which par­ents will turn their neck to­wards their neigh­bor and try to grab and twist their bill. Al­though rare, fight­ing with bills and flip­pers has been ob­served.

The fe­male lays two eggs within 3 days of each other. The eggs are kept safely under the male or fe­male for the 35 days of in­cu­ba­tion. For the first three to four weeks, the chicks are guarded in the nest. The par­ents take turns get­ting food and re­gur­gi­tat­ing it for the chicks. Near the end of this stage, the chicks begin to move short dis­tances away from the nest and form groups with other chicks (creches). These groups serve to pro­tect against preda­tors while both par­ents to for­age for the grow­ing young. The young fledge at 70 days old and will enter the sea for the first time. Both par­ents will still feed their chicks (al­though not as often) dur­ing the fledg­ing pe­riod. Feed­ings have oc­ca­sion­ally been recorded post-in­de­pen­dence. (Gales, et al., 2009; McMil­lan, 1993; Naveen, 1999; Polito and Triv­el­piece, 2008; Spils­bury and Spils­bury, 2004; Williams, 1995)

• Parental Investment
• altricial
• male parental care
• female parental care
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • male
    • female
  • protecting
    • male
    • female
• pre-weaning/fledging
  • provisioning
    • male
    • female
• pre-independence
  • provisioning
    • male
    • female

Lifes­pan/Longevity

On av­er­age, gen­too pen­guins live to be 13 years old. Most deaths occur within the first year of life, with only a 30 to 50 per­cent chance of sur­viv­ing until the next year. Be­yond the first year, sur­vival in­creases to an an­nual rate of 80 per­cent.

In cap­tiv­ity, the mean life span for P. papau is 10.5 years. Some in­di­vid­u­als have lived to be older; how­ever there are many deaths due to weather pat­terns (for out­side ex­hibits) and for not main­tain­ing a suf­fi­cient diet for the pen­guins. (Gai­ley-Phipps, 1978; Gilpin, 2007; Williams, 1995)

• Average lifespan
  Status: wild

  13 years

• Average lifespan
  Status: captivity

  10.5 years

Be­hav­ior

Gen­too pen­guins are highly ter­ri­to­r­ial of their nests. For the most part, gen­too pen­guins live in the same place that they breed. The main rea­son for mov­ing lo­ca­tions is be­cause of ice for­ma­tion dur­ing the win­ter months, in which case they will move to an ice-free lo­ca­tion.

After the chicks have fledged and made their final de­par­ture from the nest­ing site, adult gen­toos begin their an­nual molt. The pre-molt pe­riod be­gins in Jan­u­ary when the adults go out to sea for long for­ag­ing trips. They make fre­quent trips and rapidly gain weight to reach max­i­mum mass at this point of the year. Molt­ing is an en­ergy in­ten­sive event, and pen­guins must gorge them­selves to build up fat re­serves. This pre-molt pe­riod lasts for around 55 days. The ac­tual molt­ing stage lasts 25 days. Dur­ing this time, P. papau can­not make for­ages out to sea and must fast, los­ing about 200 grams a day. Gen­toos typ­i­cally move away from the nest­ing site to molt. (McMil­lan, 1993; Williams, 1995)

• Key Behaviors
• terricolous
• natatorial
• diurnal
• motile
• sedentary
• territorial
• colonial

• Average territory size

  1 m^2

Home Range

Gen­too pen­guins do not de­fend any ter­ri­tory ex­cept the area di­rectly around the nest, av­er­ag­ing 1 square meter in size. (McMil­lan, 1993)

Com­mu­ni­ca­tion and Per­cep­tion

Vi­su­ally speak­ing, gen­too pen­guins see ex­cel­lently un­der­wa­ter, al­though they are im­paired when on land. Their reti­nas are very sen­si­tive to the col­ors seen un­der­wa­ter such as green, blue, and pur­ple. How­ever this vi­sion be­comes im­paired once they reach the sur­face of the water.

Gen­too pen­guins com­mu­ni­cate with each other through a squawk­ing vo­cal­iza­tion. These calls typ­i­cally are higher pitched and louder in males. Gen­toos vo­cal­ize for a va­ri­ety of rea­sons for ex­am­ple, when a male or fe­male re­turns after feed­ing they will point their beaks straight up into the air and bel­low out squawks to an­nounce their re­turn.

Dur­ing in­cu­ba­tion the par­ents take turns sit­ting on the eggs. When the other par­ent re­turns (mainly from feed­ing), a se­ries of dis­plays ensue. The ar­riv­ing pen­guin does ei­ther a loud dis­play in which he/she bel­lows out into the air or can do a bow­ing dis­play in which the pen­guin bows down to the nest and gives a low hiss­ing sound. Ei­ther of these dis­plays com­mu­ni­cates to the pen­guin on the egg that the re­turn­ing pen­guin is ready to watch over the nest. The change-over of the nest be­tween par­ents usu­ally takes three min­utes. Some­times, the dis­plays are rec­i­p­ro­cated by the cur­rent in­cu­ba­tor.

At times dur­ing the mat­ing sea­son, the male will rub the fe­male's face and then the two of them will rub their bills to­gether. Also, when one re­turns to the breed­ing ground with a stone to use for the nest, the other will bow re­peat­edly to ac­cept the stone. These dis­plays likely serve to strengthen the pair bond.

Gen­too pen­guins will also make sounds when an­other pen­guin is en­croach­ing on its ter­ri­tory. Gen­toos will make low hiss­ing sounds if the in­ter­ac­tion is not a high threat level. As a threat looms closer, gen­toos will let out grunts.

Chicks com­mu­ni­cate with their par­ents when they want food with high-pitched chirp­ing sounds. In other sit­u­a­tions, chicks make a mod­i­fied whis­tle call until they reach their first molt where they de­velop the adult call. Chicks can dis­tin­guish their par­ents call apart from the calls of the thou­sands of other gen­toos that may be nest­ing within the colony. Like all birds, gen­too pen­guins per­ceive their en­vi­ron­ments through vi­sual, au­di­tory, tac­tile, and chem­i­cal stim­uli. (McMil­lan, 1993; Müller-Schwarze and Müller-Schwarze, 1980; Naveen, 1999; Williams, 1995)

• Communication Channels
• visual
• tactile
• acoustic

• Other Communication Modes
• duets

• Perception Channels
• visual
• tactile
• acoustic
• chemical

Food Habits

Gen­too pen­guins are car­ni­vores and mainly con­sume fish, crus­taceans, and cephalopods. Dif­fer­ent times of the year mark dif­fer­ent per­cent­ages of their diet. Krill (Eu­phau­sia val­len­tini) and shrimp (Nau­ti­caris mar­i­oni) make up most of the crus­tacean diet. In Feb­ru­ary and March, crus­taceans make up about 10% of their diet but from March to June it jumps to 75%. All other times of the year, crus­taceans are ab­sent from their diet.

From June to Oc­to­ber, rock­cod (Lep­i­dono­tothen squam­ifrons) make up 90% of their diet, but they also con­sume uni­corn ice­fish (Chan­nichthys rhinocer­a­tus). Cephalopods only make up 10% of their diet dur­ing the year. The main types of cephalopods for­aged on are oc­topi and some­times small squid. The sea­sonal diet vari­a­tion is due the pres­ence of other pen­guin species dur­ing breed­ing sea­son, sea­sonal mi­gra­tion of prey, as well as the avail­abil­ity of prey at vary­ing depths. Most other pen­guins for­age in deeper wa­ters which will push some prey species closer to shore and into the prime range for gen­toos.

Gen­too pen­guins feed in shal­low re­gions. When they are un­der­wa­ter, their meta­bolic rate slows down en­abling them to stay un­der­wa­ter for longer pe­ri­ods to for­age.

Dur­ing the chick-rear­ing stage, par­ent gen­toos will re­turn to the nest and re­gur­gi­tate their freshly caught food for their chicks to eat. (Adams and Klages, 1989; McMil­lan, 1993)

• Primary Diet
• carnivore
  • piscivore

• Animal Foods
• fish
• mollusks
• aquatic crustaceans

Pre­da­tion

Young chicks are at much greater risk of pre­da­tion than adults. Brown skuas (Cathar­acta lonnbergi) are the main preda­tors of pen­guin chicks. Skuas mainly feed on the chicks and eggs found along the edge of the pop­u­la­tion which are per­ceived as weak and soli­tary. The for­ma­tion of chick crèches act as an anti-preda­tor-de­fense. Skuas are less likely to at­tack the crèches of gen­too chicks be­cause it is hard to dis­tin­guish where one chick is within a group.

In the water, wad­dell seals (Lep­tony­chotes wed­del­lii) have been seen feed­ing on gen­toos. Leop­ard seals (Hy­drurga lep­tonyx) will travel in the gen­too breed­ing grounds and at­tack pen­guins leav­ing and re­turn­ing to the colony. They are most often seen eat­ing chicks as they first enter the water dur­ing fledg­ing. Other species of seals such as fur seals from the genus Arc­to­cephalus and south­ern sea-li­ons from the genus Otaria have been ob­served eat­ing gen­toos, al­though their im­pact on the pop­u­la­tion is un­known.

The main adap­ta­tion to evade preda­tors is coun­ter­shad­ing. Aquatic preda­tors can look down and see the black dor­sal side of the gen­too, which blends in with the ocean floor. Like­wise, seals look­ing up see the white ven­tral side, which blends in with the light from the sky. (Cob­ley and Bell, 1998; Em­slie, et al., 1995; McMil­lan, 1993; Williams, 1995)

• Anti-predator Adaptations
• cryptic

• Known Predators

  • Brown skuas (Catharacta lonnberg)
  • Waddell seals (Leptonychotes weddellii)
  • Leopard seals (Hydrurga leptonyx)
  • Fur seals (Arctocephalus)
  • Southern sea-lions (Otaria)

Ecosys­tem Roles

Gen­toos live in colonies with other gen­toos, but are also known to live in colonies with other pen­guin species. Al­though the species all for­age in the ocean, dif­fer­ent species are par­ti­tioned to for­age at dif­fer­ent depths or dis­tances. P. papau do not neg­a­tively af­fect other pen­guin species since they mainly for­age right off­shore.

Be­cause gen­toos live in large colonies with thou­sands of birds, flea and tick preva­lence is high. Fleas from the genus Para­p­syl­lus are com­mon. The most preva­lent tick is Ixodes uriae, which mainly af­fects the ex­posed skin of chicks such as ear canals, feet, and faces.

Ces­todes, mem­bers of the genus Tetra­both­rius, have been found in the in­testines of Py­goscelis papau but lit­tle is known about their life cycle. The ces­todes are found in var­i­ous crus­taceans that make up the gen­toos' diet. Mem­bers of the genus Coryno­soma also have been re­ported in gen­toos.

Paror­chites zed­eri, an­other species of ces­tode, latches onto the in­side of gen­toos' in­testines. These par­a­sites cre­ate small pouches in the in­testines and in­sert their pseu­doscole­ces ("false heads") in them to feed. The areas that P. zed­eri latch onto in­crease in vol­ume due to the cre­ation of more in­testi­nal cells and blood flow to the area in­creases. (Duig­nan, 2001; Tzvetkov, et al., 1999; Williams, 1995)

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

Pen­guins have been hunted for their blub­ber, which can be pu­ri­fied to oil and used for fuel. Hun­dreds of thou­sands of pen­guins were killed for their blub­ber, with some breed­ing colonies be­com­ing ob­so­lete. Gen­too skins are also col­lected and used to make caps, clothes, slip­pers, and purses. In the late 1980's, egg col­lect­ing was pop­u­lar by sailors and by lo­cals. These eggs also were con­sumed in large quan­ti­ties. (John­son, 1981; Pe­ter­son, 1979; Williams, 1995)

• Positive Impacts
• body parts are source of valuable material

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

There are no known ad­verse ef­fects of Py­goscelis papau on hu­mans.

Con­ser­va­tion Sta­tus

The world­wide gen­too pen­guin pop­u­la­tion is sta­ble with around 628,000 in­di­vid­u­als. Some of these colonies are in­creas­ing mod­er­ately while oth­ers are de­clin­ing rapidly. The con­stant, and some­times dras­tic, changes in pop­u­la­tion size has gen­toos listed as "Near Threat­ened" on the IUCN Red List. There are cur­rently no con­ser­va­tion ef­forts in ac­tion, al­though some pro­pos­als sug­gest ex­tend­ing long-term ob­ser­va­tions on breed­ing colonies to limit dis­tur­bances of nest­ing sites. Pro­tected areas have been set up in gen­too breed­ing grounds, in­clud­ing those on Mac­Quarie Is­land and Heard Is­land. ("Py­goscelis Papau", 2010; Schafer, 2000)

• IUCN Red List

  Near Threatened
  More information

• IUCN Red List

  Near Threatened
  More information

• CITES

  No special status

Con­trib­u­tors

Kier­sten Newtoff (au­thor), Rad­ford Uni­ver­sity, Karen Pow­ers (ed­i­tor), Rad­ford Uni­ver­sity, Rachelle Ster­ling (ed­i­tor), Spe­cial Pro­jects.

Ref­er­ences

2010. "Py­goscelis Papau" (On-line). The IUCN Red List of Threat­ened Species. Ac­cessed Oc­to­ber 23, 2010 at http://​www.​iucnredlist.​org/​apps/​redlist/​details/​144800/​0.

Adams, N., N. Klages. 1989. Tem­po­ral vari­a­tion in the diet of the gen­too pen­guin Py­goscelis papua at sub-antarc­tic Mar­ion Is­land. Colo­nial Wa­ter­birds, 12/1: 30-36.

Adams, N., C. Brown. 1983. Div­ing depths of the gen­too pen­guin (py­goscelis papua). The Con­dor, 85: 503-504.

Bost, C., P. Jou­ventin. 1990. Lay­ing asyn­chrony in gen­too pen­guins on Crozet Is­lands: Causes and con­se­quences. Ornis Scan­di­nav­ica, 21/1: 63-70.

Cob­ley, N., G. Bell. 1998. Wed­dell seal (Lep­tony­chotes wed­del­lii) feed­ing on gen­too pen­guins (Py­goscelis papau). Ma­rine Mam­mal Sci­ence, 14/4: 881-883.

Crox­all, J., L. Davis. 1999. Pen­guins: Para­doxes and pat­terns. Ma­rine Or­nithol­ogy, 27: 1-12.

Cuervo, J., M. Pala­cios, A. Bar­bosa. 2009. Beak coloura­tion as a pos­si­ble sex­ual or­na­ment in gen­too pen­guins: Sex­ual dichro­ma­tism and re­la­tion­ship to body con­di­tion. Polar Bi­ol­ogy, 32/9: 1305-1314.

Duig­nan, P. 2001. Dis­ease of pen­guins. Sur­veil­lance, 28/4: 5-11.

Em­slie, S., N. Karnovsky, W. Triv­el­piece. 1995. Avian pre­da­tion at pen­guin colonies on King George Is­land, Antarc­tica. The Wil­son Bul­letin, 107/2: 317-327.

Frédérique, D., F. Cézilly, M. Pagel. 1998. Mate fi­delity and colo­nial­ity in wa­ter­birds: A com­par­a­tive analy­sis. Oe­colo­gia, 116/3: 433-440.

Gai­ley-Phipps, J. 1978. A world sur­vey of pen­guins in cap­tiv­ity. In­ter­na­tional Zoo Year­book, 18/1: 7-13.

Gales, R., B. Green, J. Libke, K. New­grain, D. Pem­ber­ton. 2009. Breed­ing en­er­get­ics and food re­quire­ments of gen­too pen­guins (Py­goscelis papua) at Heard and Mac­quarie Is­lands. Jour­nal of Zo­ol­ogy, 231/1: 125-139.

Gilpin, D. 2007. Pen­guins: Lifestyle - Habi­tat - Feed­ing - Be­hav­ior. New York, NY: Par­ragon Inc.

John­son, S. 1981. Pen­guins. Min­neapo­lis, MN: Lerner Pub­li­ca­tions Co..

McMil­lan, B. 1993. Pen­guins at Home: Gen­toos of Antarc­tica. New York, NY: Houghton Mif­flin Com­pany.

Müller-Schwarze, D., C. Müller-Schwarze. 1980. Dis­play rate and speed of nest re­lief in antarc­tic Py­goscelid pen­guins. The Auk, 97/4: 825-831.

Naveen, R. 1999. Wait­ing to Fly. New York, NY: William Mor­row & Com­pany.

Pe­ter­son, R. 1979. Pen­guins. Boston: Houghton Mif­flin.

Pis­to­rius, P., N. Huin, S. Crofts. 2010. Pop­u­la­tion change and re­silience in gen­too pen­guins Py­goscelis papua at the Falk­land Is­lands. Ma­rine Or­nithol­ogy, 38/1: 49-53.

Polito, M., W. Triv­el­piece. 2008. Tran­si­tion to in­de­pen­dence and ev­i­dence of ex­tended parental care in the gen­too pen­guin (Py­goscelis papua). Ma­rine Bi­ol­ogy, 154/2: 231-240.

Quin­tana, R. 2001. Nest-site char­ac­ter­is­tics of a gen­too pen­guin Py­goscelis papau colony at Cierva Point, Antarc­tic Penin­sula. Ma­rine Or­nithol­ogy, 29/2: 109-112.

Quin­tana, R., V. Cirelli. 2000. Breed­ing dy­nam­ics of a gen­too pen­guin Py­goscelis papau pop­u­la­tion at Cierva Point, Antarc­tic Penin­sula. Ma­rine Or­nithol­ogy, 28/1: 29-35.

Ren­ner, M., J. Va­len­cia, L. Davis, D. Saez, O. Ci­fuentes. 1998. Sex­ing of adult gen­too pen­guins in Antarc­tica using mor­pho­met­rics. Colo­nial Wa­ter­birds, 21/3: 444-449.

Schafer, K. 2000. Pen­guin Planet: Their World, Our World. Min­netonka: North­wood Press.

Spils­bury, R., L. Spils­bury. 2004. A Rook­ery of Pen­guins. Chicago, IL: Heine­mann Li­brary.

Tzvetkov, Y., A. Kril, B. Georgiev, N. Chipev. 1999. Mor­phol­ogy of le­sions in the in­testi­nal wall of gen­too pen­guin, Py­goscelis papau, caused by Paror­chites zed­eri. Bul­gar­ian An­ar­c­tic Re­search, 2: 62-67.

Williams, T. 1995. The Pen­guins: Sphenis­ci­dae. New York, NY: Ox­ford Uni­ver­sity Press.