Klemens Pütz

Population trends, breeding success and diet composition of gentoo Pygoscelis papua, magellanic Spheniscus magellanicus and rockhopper Eudyptes chrysocome penguins in the Falkland Islands. A review

Abstract. Data on population size, breeding success and diet composition of gentoo (Pygoscelis papua), magellanic (Spheniscus magellanicus) and rockhopper (Eudyptes chrysocome) penguins, collected as part of the Falkland Island Seabird Monitoring Programme from 1986/1987 to 1998/1999, were analysed with regard to spatial and temporal variation, as well as potential interaction with local commercial fisheries. No significant population trends were detectable, mainly because of the short time-series and large spatial and inter-annual variation in the number of breeding pairs in the colonies monitored. However, the breeding success of all three penguin species has improved slightly over the last few years, indicating a potential for increasing populations in the near future. During the breeding season, all three penguin species preyed opportunistically on a mixture of fish, squid and crustaceans. Diet composition too showed a high degree of spatial and temporal variation. However, in all three penguin species studied, squid gradually disappeared from the diet over successive years, to be replaced by fish. Coincidentally, the commercial catches of the squid species Loligo gahi in Falkland Islands waters decreased and the by-catch of nototheniid fish increased. All three penguin species compete directly with the commercial fishing fleet for L. gahi; however, there may also be competition for Patagonian toothfish (Dissostichus eleginoides), hake (Merluccius sp.) and southern blue whiting (Micromesistius australis), because juveniles of these species were found regularly in penguin diets.

Re-evaluation of Historical Rockhopper Penguin Population Data in the Falkland Islands

Abstract Over the past 70 years, three counts have been conducted on the Rockhopper Penguin (Eudyptes chrysocome) population on the Falkland Islands during the 1932/33, 1995/96 and 2000/01 breeding seasons. The results indicated a population decrease of more than 90% during this period, from more than three million breeding pairs in 1932/33 to less than 300,000 breeding pairs in the mid-1990s. However, a re-evaluation of these data revealed that the original population was substantially overestimated and the 1930s numbers were probably closer to 1.5 million breeding pairs. Modifications to the mid-1990s data produce a revised population estimate of about 263,000, rather than 297,000 breeding pairs. Based on these revised values, the overall decrease in the Rockhopper Penguin at the Falkland Islands between 1932 and 1995 still exceeded 80%, at a rate of ca. 2.75% per annum. In the most recent census, the population was estimated to be 272,000 breeding pairs, suggesting a stable population since the mid 1990s. These re-calculations of historical Rockhopper Penguin population trends in the Falkland Islands have important implications for the assessment of the global population size and long-term trends of this species.

Summer diet of king penguins (Aptenodytes patagonicus) at the Falkland Islands, southern Atlantic Ocean

Abstract. The diet of king penguins (Aptenodytes patagonicus) brooding chicks was investigated during February 2001 at the Falkland Islands, where a small but increasing population is located at the limit of the breeding range of this species. Fish was the most important food source by number (98.0%) and reconstituted mass (97.8%), squids accounting for the remainder. Myctophid fishes represented the main part of the diet (97.7% by number and 96.6% by reconstituted mass), Protomyctophum choriodon being by far the main prey item (84.2% and 88.1%, respectively). Four other myctophids and one squid species each contributed to more than 1% of the diet by number: Krefftichthys anderssoni (4.8%), Electrona carlsbergi (4.6%), Gymnoscopelus nicholsi (2.2%) and Protomyctophum tenisoni (1.8%), together with small juveniles of Gonatus antarcticus (1.8%). Twelve squid species were identified from accumulated lower beaks, including the ommastrephid Martialia hyadesi (48.3% by number), the onychoteuthids Moroteuthis ingens (15.6%), Kondakovia longimana (10.5%) and Moroteuthis knipovitchi (7.3%), and Gonatus antarcticus (9.2%). The stable-carbon and stable-nitrogen isotopic composition of chick food and adult blood differed in a way that suggests that, during the same trip, adult birds fed for themselves in distant foraging grounds, and fed for their chicks on their way back to the colony. The study emphasizes that king penguins are specialist myctophid eaters throughout their breeding range in summer, and highlights the importance of Protomyctophum choriodon as a link between zooplankton and top predators in the pelagic ecosystem of the southwestern Atlantic Ocean.

Sexual differences in the foraging behaviour of Magellanic Penguins related to stage of breeding

Abstract Understanding the foraging behaviour of seabirds and its plasticity is vital to establish their role in marine food webs and their use as indicators of change in the availability of prey. The foraging behaviour of penguins is known to differ with locality, sex, stage of breeding and between years. We studied the diving behaviour of breeding Magellanic Penguins (Spheniscus magellanicus), using time-depth recorders, during incubation and brooding in the 2003–04 and 2004–05 breeding seasons at Isla Martillo, Tierra del Fuego, Argentina. Foraging trips during the incubation period were longer than those during the brooding period for both sexes in both years of the study. Sex-related differences in foraging behaviour were observed during the incubation stage. During the incubation stage females performed longer foraging trips than males, foraging effort was lower, and did not dive as deep as males in both years. Foraging success was lower for females than males during incubation only in 2003. Our results suggest that sexual differences, expressed as differences in the foraging parameters of males and females, only develop when Fuegian Sprat (Sprattus fuegensis), the main prey in this locality, is not abundant close to the colony. Females may be extending the volume of water they can exploit by extending the duration of trips (horizontal distance), whereas males do so by diving deeper (vertical distance). Our results show the fundamental differences in foraging strategies between the sexes in Magellanic Penguin are a consequence of environmental conditions not morphological differences between sexes.

Post-Fledging Dispersal of King Penguins (Aptenodytes patagonicus) from Two Breeding Sites in the South Atlantic

Most studies concerning the foraging ecology of marine vertebrates are limited to breeding adults, although other life history stages might comprise half the total population. For penguins, little is known about juvenile dispersal, a period when individuals may be susceptible to increased mortality given their naïve foraging behaviour. Therefore, we used satellite telemetry to study king penguin fledglings (n = 18) from two sites in the Southwest Atlantic in December 2007. The two sites differed with respect to climate and proximity to the Antarctic Polar Front (APF), a key oceanographic feature generally thought to be important for king penguin foraging success. Accordingly, birds from both sites foraged predominantly in the vicinity of the APF. Eight king penguins were tracked for periods greater than 120 days; seven of these (three from the Falkland Islands and four from South Georgia) migrated into the Pacific. Only one bird from the Falkland Islands moved into the Indian Ocean, visiting the northern limit of the winter pack-ice. Three others from the Falkland Islands migrated to the eastern coast of Tierra del Fuego before travelling south. Derived tracking parameters describing their migratory behaviour showed no significant differences between sites. Nevertheless, generalized linear habitat modelling revealed that juveniles from the Falkland Islands spent more time in comparatively shallow waters with low sea surface temperature, sea surface height and chlorophyll variability. Birds from South Georgia spent more time in deeper waters with low sea surface temperature and sea surface height, but high concentrations of chlorophyll. Our results indicate that inexperienced king penguins, irrespective of the location of their natal site in relation to the position of the APF, develop their foraging skills progressively over time, including specific adaptations to the environment around their prospective breeding site.

Comparative foraging behaviour of sympatric Humboldt and Magellanic Penguins reveals species-specific and sex-specific strategies

Abstract How closely related marine organisms mitigate competition for resources while foraging at sea is not well understood, particularly the relative importance of interspecific and intraspecific mitigation strategies. Using location and time—depth data, we investigated species-specific and sex-specific foraging areas and diving behaviour of the closely related Humboldt (Spheniscus humboldti) and Magellanic (S. magellanicus) Penguins breeding in sympatry at Islotes Puñihuil in southern Chile during the chick-rearing period. The average duration of foraging trips was <20 h and did not differ significantly between species or between sexes of each species. Magellanic Penguins made significantly deeper and longer dives than Humboldt Penguins. Males of both species made significantly longer dives than females. Total distance travelled per foraging trip was significantly greater for males than for females, and females made more direct trips (less sinuous) than males. Foraging effort was concentrated in waters up to 15 km to the west and south-west of the colony. The overlap in density contours was lower between species than between sexes within a species. In general, dive characteristics and foraging areas differed more between Magellanic and Humboldt Penguins than between the sexes of each species. In contrast to the findings of studies of flying seabirds, the foraging behaviour of these penguins differs more between species than between sexes.

Aspects of the Breeding Biology of the Magellanic Penguin in the Falkland Islands

Abstract The breeding biology of the Magellanic Penguin (Spheniscus magellanicus), including the timing of laying, brooding and fledging, foraging trip lengths during incubation and brooding and diet in relation to breeding success, was investigated at Volunteer Beach in the north east of the Falkland Islands during the 2001/02 breeding season. Egg-laying dates were between 12 October and 1 November, with an overall hatching success of 65%. The length of foraging trips during incubation ranged from 2-15 days. Chicks were provisioned daily during the 23 day brood period, and then at a mean interval of two days during the unattended period, until fledging occurred in late January and early February. Successful pairs laid significantly earlier and undertook shorter foraging trips during incubation and brooding compared to unsuccessful pairs. The mean breeding success of 0.2 chicks/pair was low compared to the ten year mean at the study site and was possibly due to a lower abundance of squid, which is the preferred food for Magellanic penguin chicks in the Falkland Islands. The results obtained are discussed with regard to the breeding biology of the Magellanic Penguin on the mainland of South America. However, further research in subsequent seasons is required to determine whether the observed differences in breeding biology compared to elsewhere in the species range is typical behavior or the result of the changed prey availability.

Entanglement and drowning of a Magellanic Penguin (Spheniscus magellanicus) in a gill net recorded by a time-depth recorder in South-Central Chile

Abstract. Various mitigation measures have been implemented to reduce incidental seabird mortality in longline and trawl fisheries but little attention has been given to artisanal fishing. In the 2008/09 breeding season, during a study of foraging of Humboldt, Spheniscus humboldti, and Magellanic Penguins, S. magellanicus, breeding on Puñihuil islets, southern Chile, a Magellanic Penguin equipped with a time-depth recorder became entangled and subsequently drowned in a gill net set for Corvina Drum (Cilus gilberti). The device was returned by fishermen and the data appear to be the first documented case of such a drowning in a marine, air-breathing vertebrate. According to the data, while diving to a depth of more than 50 m, the bird became entangled and drowned, remaining below 60 m for nearly 21 hours until the net was hauled. Although only a single incident is reported, there are indications that incidental mortality of penguins, other seabirds and marine mammals is more common in artisanal fisheries than previously anticipated.

Heterospecific Pairing and Hybridization between Wild Humboldt and Magellanic Penguins in Southern Chile

Abstract. The Humboldt (Spheniscus humboldti) and Magellanic (S. magellanicus) Penguins overlap over 1100 km along the coast of the southeastern Pacific Ocean, and much has been hypothesized about hybridization between them. We visited Puñihuil and Metalqui islands, southern Chile (41–42° S), where both species form mixed colonies; these are also the Humboldt Penguins southernmost colonies. We observed one mixed pair attending chicks and two adults of intermediate color pattern, one of which tended a chick at a nest. Additionally, on the basis of analysis of 30 blood samples of Humboldt Penguins from the Puñihuil colony, we report the first documented Humboldt × Magellanic Penguin hybrid. Judged from the pattern of restriction fragments, this bird had a Magellanic dam and a Humboldt sire. We sequenced mitochondrial and nuclear copies independently to confirm these results. We suggest that hybridization at Metalqui and Puñihuil is encouraged by the low abundance of the Humboldt Penguin rather than by failed mate recognition.

Breeding patterns of King Penguins on the Falkland Islands

Abstract The breeding biology of the King Penguin (Aptenodytes patagonicus) has been investigated in detail at sites across its circum-subantarctic range, except at its most temperate location, the Falkland Islands. Aspects of the breeding biology of King Penguins, including timing of laying, brooding and fledging and the length of shifts during incubation and brooding, were studied in the Falkland Islands during the 2001–02 breeding season. The first peak in numbers of pre-nuptial moulting individuals occurred during October and eggs were laid from early November to mid-March. Incubation shifts lasted 10–18 days, and shifts undertaken during the 34-day brooding period were 4–9 days in duration. Foraging trips during the early crèching period were 4–16 days in duration. Chicks that hatched before 22 January reached a mean asymptotic body mass of 8.8 kg in April, while later-hatched chicks increased in mass until July but reached a significantly lower body mass of 7.7 kg. Survival of chicks over winter was high (89%), which may be associated with lower rates of avian predation and less severe weather conditions in the Falkland Islands compared with other breeding sites. Chicks began fledging in mid-November. Late breeders who laid in January and February had a high rate of breeding success. Further research is required at this most temperate colony to confirm the early timing of breeding and the high success rates of early and late breeding attempts.