Marcelo Bertellotti

CONSPECIFIC FOOD COMPETITION EXPLAINS VARIABILITY IN COLONY SIZE: A TEST IN MAGELLANIC PENGUINS

Food availability has been proposed as one of the main factors regulating population sizes in birds. Seabirds have provided evidence for the hypothesis that food depletion due to intraspecific competition explains variability in colony size. However, the predictions derived from this hypothesis have not been fully tested due mainly to the difficulties in measuring food availability in marine environments. We measured stable isotopes of nitrogen (d 15 N) and carbon (d 13 C) in the blood of Magellanic Penguins (Sphen- iscus magellanicus), which reveal information about their consumed prey and foraging habits. We tested if conspecific competition causes food depletion, affecting penguin breed- ing performance and, ultimately, the size of the colonies. Blood d 15 N values of adults and chicks significantly decreased with increasing size of their colonies and with the number of conspecifics breeding within the parental foraging ranges. This suggests that high breed- ing densities provoke the depletion of high-quality prey (mainly anchovy). We also found positive relationships between d 13 C values and density of conspecifics within the parental foraging ranges, indicating that when competition for food is high, individuals tend to feed closer to the colony on prey of lower quality. Adult d 15 N values were positively correlated with breeding success at the colonies, which was negatively correlated with the density of conspecifics within foraging ranges. Moreover, d 15 N values of fledglings were positively correlated with their body condition but not with their T-cell mediated immune response considered as two measures of their survival prospects. This decreased breeding output was translated to the colony-size structure of the population, since colony size was nega- tively correlated with the number of conspecifics breeding within the parental foraging ranges. Therefore, we provide strong evidence suggesting that density-dependent food de-

Determining Sex of Magellanic Penguins Using Molecular Procedures and Discriminant Functions

Abstract Magellanic Penguins (Spheniscus magellanicus) show little sexual dimorphism, and although males are usually larger than females, sexing by direct observation may be difficult, especially in the case of chicks. In this paper we evaluate the utility of four different PCR-based sex determination techniques using genomic DNA for sexing Magellanic Penguins. We found that the primer set designed for sex determination in Collared Flycatcher (Ficedula albicollis) also provided a reliable, simple and convenient sexing procedure for Magellanic Penguins. Additionally, we obtained discriminant functions for sexing adults and chicks, sampled at six colonies differing in size and other ecological characteristics. Discriminant function for adults used two variables, bill length and bill depth that correctly classified 97% of the birds. Discriminant function for chicks included bill length and flipper length and correctly classified 78% of the individuals. Although molecular and biometric approaches could be useful for sexing adult Magellanic Penguins, only molecular procedures proved appropriate for accurately sexing chicks.

Spatial and temporal patterns in the diet of the Kelp Gull in Patagonia

The Kelp Gull (Larus dominicanus) is an abundant and widely distributed species in coastal Patagonia, and has increased in number at many locations during the last decade. We present comparative information on diet composition between locations and diet variation throughout the breeding cycle at three Provincial Wildlife Reserves (Punta Piramide, Punta Leon, and Punta Tombo), Chubut, Patagonia. We analyzed diet using regurgitated pellets. A total of 41 types of prey were identified at the three colonies. Kelp Gulls fed throughout the season mostly on intertidal invertebrates, although fish also was an important diet component, mainly during the chick stage. The diet also included garbage, insects, and other seabird offspring. Of all types of prey, 70.7% were common to the three locations, although the pattern of consumption of the main food categories differed among locations. The average consumption of garbage differed significantly among locations, with larger amounts of garbage in the diet the closer the colony to the nearest landfill. Kelp Gulls showed a marked seasonal variation in the consumption of the main food types. At Punta Tombo and Punta Leon, there was a change from a mostly marine invertebrate diet during the pre-laying and incubation stages to a mainly fish diet during the chick stage. The consumption of the main food categories was significantly different between seasons at Punta Piramide but was similar at the other two colonies.

USE OF TIPS BY NESTING KELP GULLS AT A GROWING COLONY IN PATAGONIA

Abstract We evaluated the magnitude of use of waste tips by Kelp Gulls (Larus dominicanus) nesting at Isla de los Pájaros, a large and growing colony in Patagonia, Argentina, and we assessed the difference in use between tips with urban and fishery waste. We marked with color dye 1347 adult breeding Kelp Gulls to determine if they fed in urban and fishery tips and to estimate the number of birds which used those tips during incubation. Kelp Gulls were present during 100% and 64% of counts at the fishery waste tip and the urban waste tip, respectively. The number of adult gulls was always larger at the fishery waste tip (mean ± SD = 1694 ± 664) than in the urban waste tip (mean ± SD = 59 ± 68). Considering the total number of gulls flying from the colony to the tips and the proportion of marked gulls in the tips, we estimated that at least 54–69% of the birds of the colony were present at the tips. The use of fishery waste may have contributed to the increase in the number of Kelp Gulls breeding at Isla de los Pájaros, and the quality, abundance, and predictability of food disposed at the fishery waste tip could foster the use of this site relative to natural food sources located closer to their breeding colony. Removal of artificial food sources may be assessed at the Puerto Madryn and other Patagonian waste tips to reduce conflicts between human and gull populations.

Apparent Absence of Blood Parasites in the Patagonian Seabird Community: Is it Related to the Marine Environment?

-The geographic and specific distribution of avian Haematozoa is poorly understood and much basic information is still needed. Studies of blood parasites in avian communities are scarce despite of their potential for disentangling the relative importance of host-specific and ecological factors shaping blood parasite distributions. Here we present the first study of blood parasites in a breeding community of seabirds by scanning blood smears obtained from 560 birds belonging to 13 species breeding in Patagonia, Argentina. Seven of these species have not been sampled previously for blood parasites. No blood parasites were detected. The scarcity of vectors due to the marine environment and the dry conditions around the colonies is the most plausible hypothesis for explaining the apparent absence of blood parasites in the Patagonian seabird community, although other hypotheses should be examined. Received 12 December 2000, accepted 8 May 2001.

Exposure of Red Knots (Calidris canutus rufa) to Select Avian Pathogens; Patagonia, Argentina

As part of the shorebird surveillance, Red Knots (Calidris canutus rufa) were sampled in two Patagonian sites in Argentina, Río Grande and San Antonio Oeste, during 2005–2006. Cloacal swabs and serum samples were collected from 156 birds and tested by virus isolation (Newcastle disease virus), polymerase chain reaction (PCR; avian influenza virus and Plasmodium/Hemoproteus), and for antibodies to St. Louis encephalitis virus. All test results were negative.

HABITAT USE AND BREEDING DISTRIBUTION OF MAGELLANIC PENGUINS IN NORTHERN SAN JORGE GULF, PATAGONIA, ARGENTINA

Abstract We evaluated distribution and size of Magellanic Penguin (Spheniscus magellanicus) colonies in northern San Jorge Gulf, Argentina, characterizing nesting habitat at 14 islands with colonies (IC) and 28 islands without nesting penguins (INC). Digital analysis of a Landsat TM satellite image and field measurements were used to assess vegetation and substrate. The 14 breeding colonies ranged in size from 13 to 96,300 nests, and number of breeding pairs was estimated at 218,460. Colonies were only located on islands. Digital analysis of the satellite image showed that the proportion of area with shrub–steppe vegetation was significantly higher at IC than at INC (38.6 vs. 4.9%), whereas percentage of rocky substrate was lower at IC (33.6 vs. 64.8%). Percentage of vegetation cover was positively correlated with island area and with number of breeding pairs. Most nests (98.6%) were located under bushes, whereas the rest were burrows dug into the substrate. Mean size of bushes used for nesting was higher at IC (4.47 vs. 0.99 m2) as was the percentage of silt–clay substrate (47.31 vs. 1.98%). Coast minimum slopes at INC were steeper than the slopes of entrance routes at IC (27.6 vs. 5.7°). Probability of occupation of islands increased with amount of shrub-type vegetation cover and silt–clay substrate, and decreased with increasing slopes and amount of sandy substrate. Magellanic Penguins selected islands with shrub-type vegetation and soil that allow building nests with adequate cover. These results are consistent with other studies showing vegetation cover is an important nesting requirement for Magellanic Penguins.

Natural and anthropogenic factors affecting the feeding ecology of a top marine predator, the Magellanic penguin

Understanding how top predators respond to natural and anthropogenically induced changes in their environment is a major conservation challenge especially in marine environments. We used a multidisciplinary approach to explore the mechanisms through which a typical central-place forager, the Magellanic penguin (Spheniscus magellanicus) from the Chubut province of Argentina, responds to variations in oceanic conditions and prey resources. We combined habitat and species distribution modeling with isotopic dietary reconstructions based on blood δ13C and δ15N values to quantify the role of bathymetry, sea-surface temperature and chlorophyll-a concentration, abundance of conspecifics, and extent of fisheries activities in explaining the foraging and feeding ecology of individuals breeding at different colonies. The at-sea distribution of penguins was tightly coupled with the spatial distribution of their staple prey species, anchovies (Engraulis anchoita), especially in areas over the continental shelf (>200 m depth), with relatively warm water (from 16° to 21°C), and moderate abundances of conspecifics (from 50 to 250 individuals). Competition with conspecifics and human fisheries were also identified as important factors explaining penguin diet with decreasing relative contributions of anchovies with increasing abundance of conspecifics and fishing activity. Our multifactorial approach allowed us to simultaneously explore different physical, biological and anthropogenic features likely affecting marine resource availability, and, consequently, driving the feeding and foraging ecology of this central-place forager. Our approach can be extended to a large suite of central-place foragers, thus providing important advances in the way we investigate how to effectively conserve and manage these species.

First record of Babesia sp. in Antarctic penguins

This is the first reported case of Babesia sp. in Antarctic penguins, specifically a population of Chinstrap penguins (Pygoscelis antarctica) in the Vapour Col penguin rookery in Deception Island, South Shetlands, Antarctica. We collected peripheral blood from 50 adult and 30 chick Chinstrap penguins. Examination of the samples by microscopy showed intraerythrocytic forms morphologically similar to other avian Babesia species in 12 Chinstrap penguin adults and seven chicks. The estimated parasitaemias ranged from 0.25×10(-2)% to 0.75×10(-2)%. Despite the low number of parasites found in blood smears, semi-nested PCR assays yielded a 274 bp fragment in 12 of the 19 positive blood samples found by microscopy. Sequencing revealed that the fragment was 97% similar to Babesia sp. 18S rRNA from Australian Little Penguins (Eudyptula minor) confirming presence of the parasite. Parasite prevalence estimated by microscopy in adults and chicks was higher (24% vs. 23.3%, respectively) than found by semi-nested PCR (16% vs. 13.3% respectively). Although sampled penguins were apparently healthy, the effect of Babesia infection in these penguins is unknown. The identification of Babesia sp. in Antarctic penguins is an important finding. Ixodes uriae, as the only tick species present in the Antarctic Peninsula, is the key to understanding the natural history of this parasite. Future work should address the transmission dynamics and pathogenicity of Babesia sp. in Chinstrap penguin as well as in other penguin species, such as Gentoo penguin (Pygoscelis papua) and Adélie penguin (Pygoscelis adeliae), present within the tick distribution range in the Antarctic Peninsula.

Leucocyte Levels in Some Antarctic and Non-Antarctic Penguins

Summary. We studied leucocyte levels in several Antarctic and non-Antarctic penguins. A total of 107 blood samples of chinstrap Pygoscelis antarctica, gentoo P. papua and Adélie P. adeliae penguins at Isla 25 de Mayo/King George Island (South Shetland Islands, Antarctica) and Magellanic penguins Spheniscus magellanicus at Península Valdés (Chubut, Argentina), were collected and analysed during the 2009–2010 breeding season. We observed that chinstrap and Adélie penguins had lower total leucocyte counts than Magellanic and gentoo penguins. We provide some potential explanations for species differences in leucocyte levels.