Papers by Guillermo Luna-Jorquera
Waterbirds, 2004
While Isla Chañaral (29°02'S) in Chile has long been recognized as one of the most important bree... more While Isla Chañaral (29°02'S) in Chile has long been recognized as one of the most important breeding islands for the Humboldt Penguin, the reported numbers of birds there never exceeded 3,500 breeding individuals in the last two decades. However, in 2002, a one-day survey found considerably more penguins present on Isla Chañaral, which exceed the world population estimate for the species (3,300-12,000 birds). Between 9 and 14 February 2003 we conducted a census of the Humboldt Penguin on Isla Chañaral. Two different survey methods were combined to assess the number of penguins. Terrestrial or surface counts were used to survey penguins on open plains or beaches. Small area surveys of randomly established quadrats were conducted to assess the density of penguins in nests and the total number of nest sites. Results from small area surveys were extrapolated using surface size ratios of counting quadrats vs. entire nesting sectors. We determined that approximately 22,000 adult Humboldt Penguins, 3,600 chicks and 117 juveniles were present on the island during the survey. The results were much higher than any previously published estimate. Natural processes alone cannot account for an increase, and penguin numbers on Isla Chañaral previously have been underestimated. The results correspond well with recent publications that suggest that Humboldt Penguin numbers in Chile have been underestimated in the past due to inappropriate or inconsistent census methods. There are concerns about the current protection status of the island in light of its fragility and importance as the premier breeding location of the Humboldt Penguin along its entire distributional range.
Marine Ecology-progress Series, 2000
As one of the elements for a model on the food requirements of Humboldt penguins Spheniscus humbo... more As one of the elements for a model on the food requirements of Humboldt penguins Spheniscus humboldti we determined, via gas respirometry, metabolic rates while swimming and resting in water. During rest in water at 19°C Humboldt penguins (mean body mass 3.6 kg) required 5.95 W kg -1 . This corresponds to a thermal conductance in water of 0.2975 W (kg °C) -1 (at T a 19°C and assuming a T b of 39°C). When swimming in a 20 m long channel, metabolism rose from 8 W kg -1 at a speed of 0.6 ms -1 to 23.1 W kg -1 at 2.2 m s -1 . Transport costs (the cost to move 1 kg of body mass over a distance of 1 m) reached a minimum at 1.4 ms -1 with 8.1 J (kg m) -1 , which corresponds to 0.89 J (Nm) -1 . We corrected for acceleration and deceleration in the channel to determine transport costs of free-ranging Humboldt penguins travelling at sea, which were calculated as 7 J (kg m) -1 (0.71 J [Nm] -1 ), at 1.7 m s -1 . Birds feeding chicks need to balance the costs of either (1) returning to the breeding island for the night and travelling back to the feeding grounds in the morning or (2) incurring increased thermoregulatory costs associated with resting at sea overnight. Simple calculations show that at water temperatures of 19°C we expect Humboldt penguins to show a tendency to remain at sea overnight if foraging areas are > 4 km from their island. In colder waters (12°C), this distance increases to > 9 km. Using previously published data on at-sea activity of Humboldt penguins, we found that foraging costs during chick rearing amount to 340 g anchovies d -1 . Finally, we present a general model to convert Humboldt penguin activity data at sea to food requirements.
Marine Ecology-progress Series, 1998
VHF telemetry was used in November and December 1995 on 8 Humboldt penguins Spheniscus humboldti ... more VHF telemetry was used in November and December 1995 on 8 Humboldt penguins Spheniscus humboldti breeding at Pan de Azucar Island (26"s. 70" W), Northern Chile, to determine atsea behaviour of the birds. We obtained 2710 locations, 90% of which were within a radius of 20 km around the island. Mean travelling speed of the birds was 0.92 m S-' and speed distribution showed peaks at 1.6 and 3 m S-' Penguins travelling between foraging areas remained submerged for an average of 8.4 s between surfacings, whereas foraging dives lasted on average 61 s. The analysis of 79 complete foraging trips showed that tracks deviated from a straight course, and range (maximum distance from island) was only 0.37 times total horizontal distance swum. Birds did not forage synchronously or in the same foraging areas However, foraging ranges were correlated between birds, indicating similar search strategies during periods of low food availability. The results obtained here via VHF telemetry agrrcd well with those of prevlous studies employing satellitr transmitters and data loggers.
Journal of Ornithology, 1995
Penguins have a variety of ennemies both on on land and at sea. This is the first account of vamp... more Penguins have a variety of ennemies both on on land and at sea. This is the first account of vampire bats (Desmodus rotundus) preying on juvenile Humboldt Penguins (Spheniscus humboldti). Because of the nightly drain of blood by vampires, and because vampires transmit diseases from one prey species to another, this form of predation may be an important mortality factor. Pinguine haben eine Vielzahl von Feinden, sowohl im Wasser als auch an Land. Dies ist der erste Hinweis darauf, daß Vampirfledermäuse (Desmodus rotundus) sich vom Blut von Humboldtpinguinküken (Spheniscus humboldti) ernähren. Wegen der nächtlichen Blutverluste durch Vampirfledermäuse, und weil diese Blutsauger Krankheitserreger zwischen ihren Wirten übertragen können, könnte diese Form des Parasitismus einen wichtigen Mortalitätsfaktor darstellen.
Journal of Ornithology, 1997
Ices Journal of Marine Science, 2004
Factors affecting seabird distribution in the Humboldt Current upwelling system in northern Chile... more Factors affecting seabird distribution in the Humboldt Current upwelling system in northern Chile were studied in January 1999 using ship transect counts. Of 24 species recorded, the Peruvian booby (Sula variegata), the kelp gull (Larus dominicanus) and the Humboldt penguin (Spheniscus humboldti) were the most abundant. Species composition varied among different areas of the system and distribution patterns differed substantially among eight of the more abundant species. Most species showed links to variation in environmental factors (trawler distribution, SST and chlorophyll concentration). Principal component analysis identified a feeding-flock factor as the most important one for explaining observed distribution patterns. One-third of all birds recorded were associated in feeding flocks and 3% of all individuals were directly attending fishing vessels.
Waterbirds, 2005
The feeding ecology of the Kelp Gull ( Larus dominicanus ) was studied during the 2002-03 breedin... more The feeding ecology of the Kelp Gull ( Larus dominicanus ) was studied during the 2002-03 breeding season at Coquimbo, northern Chile. Food composition was studied by analyzing pellets regurgitated by Kelp Gulls living in different habitats. Birds breeding or resting near fishing ports used these as their main feeding grounds. Birds breeding on offshore islands fed mainly on intertidal organisms and olives. A comparison between the food of breeders and non-breeding birds during the breeding season showed a difference in diet composition of breeders, who fed more on fish of high energy density while non-breeding birds continued feeding on a wide range of organisms and waste. Observations in a fishing harbor and at sea demonstrated that fisheries waste was an important food source for the birds. The inshore distribution at sea was related to the location of fishing ports and breeding colonies.
Journal of Ornithology, 2011
Marine ecosystems and their inhabitants are increasingly under threat from climate change, compet... more Marine ecosystems and their inhabitants are increasingly under threat from climate change, competition with humans for resources, and pollution. Species that are endemic to particular currents or regions of the world’s oceans have the potential to be at higher risk due to localized overfishing, pollution, or locally severe impacts of climate change such as more intense, or longer, El Niño Southern Oscillation events. Understanding patterns of population differentiation in endemic marine organisms may be particularly important for their conservation and persistence. Peruvian Boobies (Sula variegata) are endemic to the Humboldt Current upwelling system and have experienced population fluctuations throughout their evolutionary history due to both dramatic reduction of food supplies, and anthropogenic influence over the last ~150 years. Recent research on other members of the Sulidae indicates that populations of these primarily tropical seabirds show a high degree of genetic differentiation; however, the sister species of the Peruvian Booby, the Blue-footed Booby (S. nebouxii), exhibits only weak range-wide population genetic structure. We characterized population genetic differentiation and diversity in 153 Peruvian Boobies using sequence variation of 540 base pairs of the mitochondrial control region and seven microsatellite loci. Although we found evidence of panmixia, a signature of isolation by distance appears to exist between the five sampled colonies. We also found unexpectedly high genetic diversity given this species’ recent population decline. Our results are similar to those for the Humboldt Penguin (Spheniscus humboldti), another endemic of the Humboldt Current upwelling system. Marine Ökosysteme und ihre Bewohner sind zunehmend bedroht durch den Klimawandel, den Wettbewerb mit Menschen um Ressourcen und durch Umweltverschmutzung. Arten, die endemisch in bestimmten Meeresströmungen oder Regionen vorkommen, sind hierbei potentiell stärker bedroht durch lokale Überfischung, Umweltverschmutzung oder lokal stark ausgeprägte Auswirkungen des Klimawandels wie z. B. intensivere oder länger andauernde El Niño Südliche Oszilllation-Ereignisse. Das Verständnis von Mustern der Populationsdifferenzierung endemischer mariner Organsimen kann von besonderer Bedeutung für ihren Schutz und ihr Weiterbestehen sein. Guanotölpel (Sula variegata) sind endemisch im Auftriebsgebiet der Humboldtströmung und haben Populationsschwankungen über ihre evolutionäre Vergangenheit auf Grund von dramatischen Reduktionen von verfügbarer Nahrung als auch durch anthropogene Einflüsse der letzten etwa 150 Jahre erfahren. Neuere Forschung an weiteren Arten der Sulidae weist auf eine hochgradige genetische Populationsdifferenzierung dieser primär tropischen Seevögel hin. Dem entgegen steht jedoch eine nur schwache genetische Populationsstruktur der Schwesterart des Guanotölpels, dem Blaufußtölpel (S. nebouxii), über dessen Verbreitungsgebiet. Wir beschreiben die genetische Populationsdifferenzierung und Diversität von 153 Guanotölpeln an Hand der Sequenzvariation einer 540 Basenpaaren langen Sequenz der mitochondrialen Kontrollregion und von sieben Mikrosatellitenmarkern. Obwohl wir Hinweise gefunden haben die auf Panmixie hinweisen, scheint ein Muster der Isolation durch Distanz zwischen den fünf beprobten Kolonien vorzuherrschen. Außerdem haben wir eine unerwartet hohe genetische Diversität gefunden, obwohl diese Art kürzlich einen Populationsrückgang erfahren hat. Unsere Ergebnisse ähneln denen die für den Humboldtpinguin (Spheniscus humboldti) gefunden wurden, einer weiteren endemischen Art des Auftriebsgebietes der Humboldtströmung.
Journal of Experimental Biology, 2003
Journal of Geophysical Research, 2003
1] We describe the spatial structure and velocity fields of two SeaWiFS-derived chlorophyll squir... more 1] We describe the spatial structure and velocity fields of two SeaWiFS-derived chlorophyll squirts in the Chilean coast. Consecutive, daily, L1A images were rectified and analyzed by means of a geographic information system. The velocity fields were obtained through feature-tracking analysis (subjective method). Both the hammerhead shape and the spatial structure of the velocity field agree with previous conceptual models. We succinctly discuss the biological consequences of squirts for the Humboldt Current coastal ecosystem.
ABSTRACT—VHF-telemetry was used in November 1995 on eight Humboldt penguins (Spheniscus humboldti... more ABSTRACT—VHF-telemetry was used in November 1995 on eight Humboldt penguins (Spheniscus humboldti) breeding at Pan de Azucar Island (26 S, 70 W), Northern Chile to determine the behaviour of the birds at sea. We obtained 2710 locations, 90% of which ...
Marine Biology, 1997
During the El Niño of 1982/1983, the Humboldt penguin population diminished dramatically in the w... more During the El Niño of 1982/1983, the Humboldt penguin population diminished dramatically in the whole distributional area of the species. Recovery of the population was slow since 1983 and it has been suggested that large numbers of Humboldt penguins die at sea, entangled in nets, or starve to death, even during non-“El Niño” years. We were able to determine for the first time, how Humboldt penguins on Pan de Azúcar Island (26°S; 72°W) utilize their marine habitat and where their feeding areas lie. For this purpose we employed two streamlined Argos satellite transmitters during the 1994/1995 and 1995/1996 breeding seasons, respectively. Mean travelling speed of Humboldt penguins during foraging trips was 0.94 m s−1 and 50% of bird positions were located within 5 km of the island (90% within 35 km). Total area covered by Humboldt penguins foraging from Pan de Azúcar Island was 12 255␣km2. Satellite transmitters also recorded dive duration; penguins spent on average 7.8 to 9 h diving per foraging day but showed no preferences for particular feeding areas. Mean daily dive durations (4-d mean) recorded during the 1994/1995 breeding season were positively correlated between birds. Significant correlation between dive duration and sea surface temperature anomalies and negative correlation between dive duration and fishery landings at nearby Caldera harbour indicate that the 1994/1995 increase in foraging effort was a response to deteriorating prey availability. Sea surface temperatures during the 1995/1996 breeding season were colder than average, and we observed no trends in bird diving activities.
Polar Biology, 1996
Analyses of cooling rates in one Adélie and one Humboldt penguin yielded calculated thermal condu... more Analyses of cooling rates in one Adélie and one Humboldt penguin yielded calculated thermal conductance values of 0.1040 and 0.1672 W(kg °C)-1, respectively. We review the methods used to calculate penguin surface area, an important component in calculating conductance values, and suggest that, in comparative studies of thermal balance, the use of body mass is a better estimator of body size than surface area. Using previously published data on penguin species, we found a significant model to predict thermal conductance from body mass according to: log C= log 0.1083−0.474 log M, where C is minimal specific thermal conductance in W(kg °C)-1 and M is body mass in kilograms.
We describe the spatial structure and velocity fields of two SeaWiFS-derived chlorophyll squirts ... more We describe the spatial structure and velocity fields of two SeaWiFS-derived chlorophyll squirts in the Chilean coast. Consecutive, daily, L1A images were rectified and analyzed by means of a geographic information system. The velocity fields were obtained through feature-tracking analysis (subjective method). Both the hammerhead shape and the spatial structure of the velocity field agree with previous conceptual models. We succinctly discuss the biological consequences of squirts for the Humboldt Current coastal ecosystem.
Journal of Ornithology, 2010
The Peruvian Booby (Sula variegata) is one of the most numerous guano bird species in the Humbold... more The Peruvian Booby (Sula variegata) is one of the most numerous guano bird species in the Humboldt Current. We used a combination of data logger deployment, at-sea observations and colony-based work to investigate the foraging and diving behaviour, as well as the at-sea distribution and food choice of Peruvian Boobies breeding at Isla Pajaros, northern central Chile. Birds foraged in the vicinity of Isla Pajaros. They performed short foraging trips, varying between a few minutes and several hours. Average foraging range was 17.1 ± 3.5 km and diving took place between 2 and 10 km off the coast. Birds dived to depth of up to 10 m with an average depth of 4.3 ± 1.5 m. By at-sea observations as well as by data logger deployment, we identified important foraging areas close to the coast, especially around protruding points. The birds’ diet was highly variable between years, with Inka scad (Trachurus murphyi) and anchovy (Engraulis ringens) being the overall dominant prey species. Despite limited sample sizes, this paper presents first results about the foraging behaviour of Peruvian Boobies at the largest breeding colony in northern Chile. This information is essential for a better understanding of the effects of environmental changes as well as for the implementation of conservation measures. The Peruvian Booby (Sula variegata) is one of the most numerous guano bird species in the Humboldt Current. We used a combination of data logger deployment, at-sea observations and colony-based work to investigate the foraging and diving behaviour, as well as the at-sea distribution and food choice of Peruvian Boobies breeding at Isla Pajaros, northern central Chile. Birds foraged in the vicinity of Isla Pajaros. They performed short foraging trips, varying between a few minutes and several hours. Average foraging range was 17.1 ± 3.5 km and diving took place between 2 and 10 km off the coast. Birds dived to depth of up to 10 m with an average depth of 4.3 ± 1.5 m. By at-sea observations as well as by data logger deployment, we identified important foraging areas close to the coast, especially around protruding points. The birds’ diet was highly variable between years, with Inka scad (Trachurus murphyi) and anchovy (Engraulis ringens) being the overall dominant prey species. Despite limited sample sizes, this paper presents first results about the foraging behaviour of Peruvian Boobies at the largest breeding colony in northern Chile. This information is essential for a better understanding of the effects of environmental changes as well as for the implementation of conservation measures.
1] We describe the spatial structure and velocity fields of two SeaWiFS-derived chlorophyll squir... more 1] We describe the spatial structure and velocity fields of two SeaWiFS-derived chlorophyll squirts in the Chilean coast. Consecutive, daily, L1A images were rectified and analyzed by means of a geographic information system. The velocity fields were obtained through feature-tracking analysis (subjective method). Both the hammerhead shape and the spatial structure of the velocity field agree with previous conceptual models. We succinctly discuss the biological consequences of squirts for the Humboldt Current coastal ecosystem.
Ices Journal of Marine Science, 2007
2007. How does a generalist seabird species use its marine habitat? The case of the kelp gull in ... more 2007. How does a generalist seabird species use its marine habitat? The case of the kelp gull in a coastal upwelling area of the Humboldt Current. -ICES Journal of Marine Science, 64: 1348-1355.
Journal of Ornithology, 2004
We examined the thermoregulatory behaviour (TRB) of roosting Humboldt penguins (Spheniscus humbol... more We examined the thermoregulatory behaviour (TRB) of roosting Humboldt penguins (Spheniscus humboldti) in north central Chile during summer and winter, when ambient temperatures (Ta) are most extreme. Each body posture was considered to represent a particular TRB, which was ranked in a sequence that reflected different degrees of thermal load and was assigned an arbitrary thermoregulatory score. During summer, birds exhibited eight different TRBs, mainly oriented to heat dissipation, and experienced a wide range of Ta (from 14 to 31°C), occasionally above their thermoneutral zone (TNZ, from 2 to 30°C), this being evident by observations of extreme thermoregulatory responses such as panting. In winter, birds exhibited only three TRBs, mainly oriented to heat retention, and experienced a smaller range of Ta (from 11 to 18°C), always within the TNZ, even at night. The components of behavioural responses increased directly with the heat load which explains the broader behavioural repertoire observed in summer. Since penguins are primarily adapted in morphology and physiology to cope with low water temperatures, our results suggest that behavioural thermoregulation may be important in the maintenance of the thermal balance in Humboldt penguins while on land.
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Papers by Guillermo Luna-Jorquera