Carlos B. Zavalaga

PATTERNS OF EGG LAYING AND BREEDING SUCCESS IN HUMBOLDT PENGUINS (SPHENISCUS HUMBOLDTI) AT PUNTA SAN JUAN, PERU

Abstract We analyzed patterns of egg laying and breeding frequency of Humboldt Penguins (Spheniscus humboldti) between 1993 and 1997 at Punta San Juan, Peru. Egg-laying extended from mid-March to the first week of December, showing two well-defined peaks in April and August–September. The extended breeding period of these birds was the result of individuals having a second clutch. About half of the females (n =189) had two clutches per year, most of which were double broods (73%). The date of completion and outcome of reproduction, or whether a change of mates occurred from the previous year, did not affect timing of egg laying. The majority of first clutches (62%) were laid in April each year. Two-clutch breeders that started laying eggs early in April had a higher breeding success than those starting in late April, and double brooders had greater success than single brooders. Two-clutch breeders started to lay eggs earlier than single-clutch breeders. Taking into account that a penguin breeding cycle (from egg laying to fledging) lasts ∼4 months, laying eggs early in April increases the chance of rearing two successful broods per year. During three consecutive years, females tended to have two clutches instead of only one clutch and an average breeding success of 4.54 fledglings over 3 years. Having as many clutches as possible when conditions are favorable appears to be a strategy used by Humboldt Penguins to maximize their lifetime reproductive success within a productive but unpredictable environment.

Health Evaluation of Free-Ranging Humboldt Penguins (Spheniscus humboldti) in Peru

Abstract As part of ongoing ecological studies of Humboldt penguins (Spheniscus humboldti) at Punta San Juan, Ica Department, Peru, health surveys were conducted in November 1992, 1993, and 1994. In the three surveys, 98 birds in total were handled for examination, and blood was collected for laboratory analysis from 90 of these birds. All birds seemed to be in good condition. Body weights of females were significantly lower in 1994 than in the other years. Fleas (Parapsyllus humboldti) and ticks (Ornithodoros amblus) were found on the penguins and in their nests. Females had significantly higher plasma calcium and phosphorus levels, and they had lower weights than males. No other differences were found between the sexes. Hematology, plasma chemistries, and plasma mineral levels varied between years. Positive antibody titers for Chlamydophila psittaci (62%), avian adenovirus (7%; 1994 only), paramyxovirus-2 (7%; 1993 only), and Salmonella Pullorum (7%) were found. Plasma chemistry and mineral levels differed between individuals testing positive vs. negative on serologic tests for avian adenovirus and Salmonella Pullorum. Serologic tests for antibodies to avian influenza A virus, avian encephalomyelitis virus, infectious bronchitis virus, avian reovirus, duck viral enteritis virus, equine encephalitis (eastern, western, and Venezuelan) viruses, infectious bursal disease virus, infectious laryngotracheitis virus, Aspergillus sp., and paramyxovirus-1 and -3 were negative. All chlorinated pesticide and polychlorinated biphenyl analyses were below detectable limits.

Male/Female Classification of the Peruvian Booby

Abstract We studied adult Peruvian Boobies (Sula variegata) on two islands in northern Peru to classify males and females using DNA-based techniques. We used this information to (1) assess the extent of size dimorphism in this species, (2) identify males and females using discriminant functions of external characters, and (3) validate use of voice as a reliable method for identifying male and female Peruvian Boobies in the field. Female Peruvian Boobies were 19% heavier and their culmens and wings were 3 and 4% larger than males, respectively. A discriminant function that included body weight and wing chord correctly classified 90% of the birds. Alternatively, 88% of correct identification of males and females was obtained with a function that incorporated only wing chord. Whistles were performed exclusively by males (25/25 of cases), whereas grunts or goose-like honk vocalizations were performed only by females (24/24 of cases). The female-larger size dimorphism of Peruvian Boobies is intermediate in comparison to other Sula boobies. Calls and biometry provide a fast, reliable, and inexpensive method for classifying most adult Peruvian Boobies as males or females in the field. We recommend a hierarchical system for classification of male and female Peruvian Boobies: (1) use of vocalizations, (2) use of body weight and wing chord when the bird did not vocalize and was weighed immediately after daybreak or before the first feeding trip of the day, and (3) use of wing chord only when there is uncertainty in temporal variations of body weight.

Status of the Humboldt Penguin in Peru, 1999-2000

Abstract The status of the Humboldt Penguin (Spheniscus humboldti) was investigated in Peru after the 1997-98 El Niño event, the strongest of the last century. Penguin numbers along the southern and central coast of Peru (97% of the total) did not differ significantly between 1999 and 2000; the average number was 4,425 individuals. In 1999, the proportion of juveniles (one-year-old birds) was only 0.2% compared with 7% in 2000, probably as a result of the 1997-98 El Niño. Penguins were found from La Foca Island (512’S) to Punta Coles (1742’S). However, the majority (78%) were clustered in five localities, Punta San Juan (36%), San Juanito Islet (11%), Hornillos Island (10%), Pachacamac Island (12%) and Tres Puertas (9%). The size and distribution of penguin colonies have changed over the last 15 years. Penguins have abandoned sites at Punta Corio, Sombrerillo and Morro Sama, and have decreased significantly in numbers in Punta San Fernando and Punta La Chira, where human disturbance has increased, mainly due to local fisheries activities. Penguins have increased at Punta San Juan, San Juanito Islet and San Gallan Island, all of which are partially protected. Half of the penguins were located in guano bird reserves, primarily at Punta San Juan. Guano bird reserves provide some protection against terrestrial predators and human disturbance; however, periodical guano extraction decreases their breeding success. Most penguin sites were found in inaccessible and marginal areas, which were vulnerable to occasional and unpredictable flooding from ocean swells. The methodology recommended by the Population and Habitat Viability Assessment workshop for a consistent census of penguins in Peru and Chile during the molting period was validated at the Punta San Juan Reserve. Continued monitoring of Humboldt Penguin numbers is recommended in order to more fully understand patterns of fluctuation and to be able to detect changes of conservation concern as early as possible. Collaborative efforts between local authorities and conservation biologists are needed to monitor and protect this vulnerable species.

Nesting sites and nest types as important factors for the conservation of Humboldt penguins (Sphensicus humboldti)

Abstract The reduction of nesting habitat has likely contributed to the decline of Humboldt penguins in Peru. We investigated the effects of using different nesting sites and nest types on the breeding success of Humboldt penguins at Punta San Juan, the largest colony in Peru, between 1993 and 1996. The majority of penguins bred on cliff tops (72%) where breeding success was high (1.03–1.18 fledglings/nest). In contrast, penguins nesting on beaches had lower breeding success (0.44–1.1 fledglings/nest), with reproductive failure mostly due to nest flooding during ocean swell years. The breeding success of penguins using surface nests (1.02–1.07 fledglings/nest) was similar to that of those using burrows (0.89–0.97 fledglings/nest) and crevices (0.85–1.15 fledglings/nest) on cliff slopes and beaches, respectively. Nevertheless, on cliff tops where the main guano deposits are located, burrows were the most successful nests (1.41 fledglings/nest). Halting guano extraction around the main breeding areas may increase the availability of burrowing substrates and, thus breeding success of this endangered species.

Hybridization between Blue-Footed (Sula nebouxii) and Peruvian (Sula variegate) Boobies in Northern Peru

Abstract. Recent reports have suggested that hybridization occurs between Blue-footed (Sula nebouxii) and Peruvian (Sula variegata) Boobies in northern Peru, but none included morphometric or genetic analyses of apparent hybrids. Over three field seasons, morphological measurements and blood samples were taken from four apparent Peruvian x Blue-footed Booby hybrids on Lobos de Tierra Island, and one apparent hybrid on the Lobos de Afuera islands. Feather samples were collected from one representative of each parental species and one hybrid. Morphological variation of apparent male hybrids was compared to 25 male Peruvian Boobies and 140 male Blue-footed Boobies, and variation in 540 base pairs of the mitochondrial control region and 8 microsatellite loci for all hybrids was compared to 141 Peruvian Boobies and 168 Blue-footed Boobies. Molecular sexing indicated that four hybrids were male and one was female. Male hybrid boobies showed weak transgressive segregation, all hybrids possessed Peruvian Booby mitochondrial DNA and microsatellite alleles from each parental species. Hybridization between these species appears rare and restricted to the islands where both species breed, and pre and post-mating barriers appear well established.

Distribution and Trends in Kelp Gull (Larus dominicanus) Coastal Breeding Populations in South America

Abstract. In South America, Kelp Gulls (Larus dominicanus) breed from Chilean Tierra del Fuego north to Río de Janeiro, Brazil, on the Atlantic coast and to Piura, Peru, on the Pacific coast. This review presents the first synthesis of information on the distribution and size of Kelp Gull colonies at the country level in coastal environments of Uruguay, Chile and Peru; provides an update on the breeding situation of the species in Brazil and Argentina; and allows the first evaluation of the overall coastal breeding population in South America. The breeding population in South America is now estimated to number at least 160,000 pairs. The largest population (at least 106,000 breeding pairs) is found in Argentina. Colonies of more than 1,000 pairs are uncommon. Population trends differed among coastal sectors, and important increases in numbers and formation of new colonies were only observed in Argentina. Available information suggests that predictable and abundant anthropogenic food subsidies, such as fishery discards and urban waste, are key factors contributing to the population growth in some coastal sectors. There is no strong evidence that Kelp Gulls are currently expanding their breeding range. However, given the population expansion in some areas and the potential conflicts with humans, ongoing monitoring efforts and population evaluations are necessary as they will provide the information required to support management decisions.

Unveiling an Important Humboldt Penguin (Spheniscus humboldti) Breeding Colony in Perú and the Need for Its Protection Against the Potential Impact of Guano Harvest

Abstract. Humboldt Penguins (Spheniscus humboldti) are globally Vulnerable due to the decline of the population and to a decline in the number of breeding sites in comparison to historical records. In 2010, we observed a few thousand Humboldt Penguins nesting in a surface-nest colony on Isla Santa Rosa in southern Perú. This number was unexpected because this site has never been listed as an important Humboldt Penguin breeding ground. We visited this island again in June 2011 and 2012, and counted 1,965 and 1,745 active nests, respectively. These numbers indicate not only the presence of at least 3,500–4,000 Humboldt Penguins, but places Isla Santa Rosa among the five largest Humboldt Penguin colonies within its entire range. The need for recognition of Isla Santa Rosa as a major Humboldt Penguin refuge is crucial for the conservation of the species, as the island has remained untouched from guano harvesting since 1996. This has resulted in a significant accumulation of guano likely to be legally collected in the next few years. Unsupervised guano harvesting could cause a Humboldt Penguin exodus and jeopardize the existence of this colony. Under this scenario, it is recommended that Isla Santa Rosa be closed to guano harvesting until a surveillance program to protect the Humboldt Penguins can be established and proven to work under the conditions found on Isla Santa Rosa.