Foraging behaviour and reproductive success in Magellanic penguins (Sphensicus magellanicus): a comparative study of two colonies

During the breeding season 1996/97 we compared the foraging and diving behaviour of adult Magellanic penguins (Spheniscus magellanicus), growth rates of their chicks and their breeding success at two colonies in the south of Chile. One of the colonies is located on Magdalena Island in the Strait of Magellan, where a commercial fishery existed several years ago; the other, on the shores of the yet unexploited Otway Sound. Thirty adult Magellanic penguins were equipped with time–depth recorders (TDR) to investigate their behaviour at sea. In each colony 15 adults returning from the sea were stomach flushed to analyse dietary composition. Chicks of TDR-nests and of 12 additional control nests were weighed regularly. Foraging effort was significantly higher at Magdalena than at Otway. The Magdalena-birds usually remained at sea overnight and foraged with a mean duration of 18 h, whereas the penguins of Otway Sound foraged during 1-d trips with a mean duration of only 9 h. Compared to Magdalena, penguins at Otway dived shallower (mean depth 14.9 vs 16.5 m), shorter (mean duration 57.8 vs 64.3 s) and showed more searching and feeding as opposed to travelling activity (on average 69 vs 55%) during the foraging trips. Compared to other breeding locations both colonies were characterised by high chick growth rates, high fledging body masses (>3 kg) and early fledging date (after 70 to 80 d), and a very high reproductive success of >1.75 chicks per breeding pair. Comparison of the diet (almost exclusively sprats) with former investigations suggests for both areas an unchanged food structure over the last decade. The results in both colonies indicate ample food availability in the season 1996/97. However, compared to the much smaller Otway colony, penguins on Magdalena have to cope with more competition for food. Therefore, future prey limitation, through resumed fishery operations or effects of El Niño, might affect the penguin population on the island more negatively than in Otway Sound

Humboldt penguins outmanoeuvring El Niño

We satellite-tracked five Humboldt penguins during the strong 1997/98 El Niño Southern Oscillation (ENSO) from their breeding island Pan de Azúcar (26 degrees 09'S, 70 degrees 40'W) in Northern Chile and related their activities at sea to satellite-derived information on sea surface temperature (SST), sea surface temperature anomaly (SSTA), wind direction and speed, chlorophyll a concentrations and statistical data on fishery landings. We found that Humboldt penguins migrated by up to 895 km as marine productivity decreased. The total daily dive duration was highly correlated with SSTA, ranging from 3.1 to 12.5 h when the water was at its warmest (+4 degrees C). Birds travelled between 2 and 116 km every day, travelling further when SSTA was highest. Diving depths (maximum 54 m), however, were not increased with respect to previous years. Two penguins migrated south and, independently of each other, located an area of high chlorophyll a concentration 150 km off the coast. Humboldt penguins seem to use day length, temperature gradients, wind direction and olfaction to adapt to changing environmental conditions and to find suitable feeding grounds. This makes Humboldt penguins biological in situ detectors of highly productive marine areas, with a potential use in the verification of trends detected by remote sensors on board satellites

The telltale heart: a non-invasive method to determine the energy expenditure of incubating Great Cormorants Phalacrocorax carbo carbo

We studied the energetics of incubating Great Cormorants Phalacrocorax carbo carbo via heart rate and respirometric measurements performed in captive and free-living animals. We applied a modified heart beat frequency (HR) monitor built for use in human athletics as well as respirometry for measurements in four captive-bred cormorants at Neumuenster Zoo, Germany. The obtained data were used to model the relationship between HR and metabolic rate (MR). The resulting correlations were MR (W kg-0.723) = 4.76 + 0.01HR (bpm) during daytime and MR (W kg-0.723) = 2.33 + 0.03HR (bpm) at night. Furthermore, the heart beat frequencies of 5 free-living, incubating cormorants at the Chausey Islands, France, were measured acoustically using artificial eggs while the activities at the nest were observed via video. HR-MR models established in the captive animals were used to determine the activity-dependent energy expenditure in these free-living cormorants. The Median MR was 5.08 W kg-0.723 at night, 6.06 W kg-0.723 while resting and sleeping during daytime, 6.20 W kg-0.723 during preening, gular flutter and unrest and 6.47 W kg-0.723 during nest building. In resting birds we found a nocturnal reduction in the energy expenditure of 16 %. Our method for measurement of heart beat frequency appears promising as a technique for determination of HR with minimal restraint to the anima

Flipper-bands on penguins: what is the cost of a life-long commitment?

The individual marking of flying and flightless birds has a long history in ornithology. It is the only technique which is cheap, simple and effective, yielding results on bird migration, age-specific annual survival and recruitment. Consequently, hundreds of thousands of birds are annually ringed worldwide. Unfortunately, researchers all too often tend to neglect problems associated with rings and tags. In Antarctic penguins, flipper bands have been used extensively by a variety of nations, and banding is an integral part of the Council for the Conservation of Antarctic Marine Living Resources' (CCAMLR) monitoring programme (Standard method A4). This programme suggests that mortality in penguins wearing bands can be attributed to either (a) prey species availability, (b) predation, (c) weather conditions or (d) other. In this paper, we have attempted to quantify energetic costs associated with wearing a flipper band. For that purpose, freshly caught Adelie penguins (n = 7) were introduced, in Antarctica, into a 21 m long still-water tunnel, where their behaviour and energy consumption were determined via observation and gas respirometry. Birds were either immediately marked with a flipper band and tested in the tunnel for ca 2 h, and then taken out and tested again after removal of the band, or vice-versa. Flipper bands significantly (ANOVA, p = 0.006) increased the power input of Adelie penguins during swimming by 24 % over the speed range of 1.4 to 2.2 m S-', from 17 W kg-' to 21.1 W kg-' (n = 115 and 157 measurements, respectively). The implications of banding on foraging performance and sunival of penguins are discussed. Implantable passive transponders could help overcome such problems

Humboldt penguins monitored via VHF telemetry

VHF telemetry was used in November and December 1995 on 8 Humboldt penguins Spheniscus humboldti breeding at Pan de Azúcar Island (26°S, 70°W), Northern Chile, to determine at-sea 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-1 and speed distribution showed peaks at 1.6 and 3 m s-1. 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 agreed well with those of previous studies employing satellite transmitters and data loggers

Monitoring Penguins at Sea using Data Loggers

The activity of four penguin species at sea was studied using new data loggers. One unit was fixed to the bird's backs and recorded swim speed, swim heading and dive depth from which the three dimensional movements of the birds at sea could be constructed by vector calculations. This unit additionally recorded sea temperature and light intensity. A further, single-channel logger was ingested by the birds and recorded stomach temperature during the periods at sea. Drops in stomach temperature were indicative of prey capture and could be ascribed to specific localities