Description: We examined how seabirds might be used to study marine environmental variables, which necessitates knowing location and the value of the variable to be studied. Five systems can potentially be used for determination of location: VHF (Very High Frequency) telemetry, PTT (Platform Terminal Transmitter) telemetry, GLS (Global Location Service) geolocation methods, dead reckoning and GPS (Global Positioning System), each with its own advantages with respect to accuracy, potential number of fixes and size. Temperature and light were used to illustrate potential difficulties in recording environmental variables. Systems currently used on seabirds for measurement of temperature respond slowly to environmental changes; thus, they may not measure sea surface temperature adequately when contact periods with water bodies are too short. Light can be easily measured for light extinction studies, but sensor orientation plays a large role in determining recorded values. Both problems can be corrected. The foraging behaviour of seabirds was also examined in order to identify those features which would be useful for determination of marine environmental variables at a variety of spatial and temporal scales. Area coverage by birds is highly dependent on breeding phase and tends to be concentrated in areas where prey acquisition is particularly enhanced. The identification of these sites may be of particular interest to marine biologists. Plungers and divers are potentially most useful for assessment of variables deeper within the water column, with some divers spending up to 90% of their time sub-surface. Few seabirds exploit the water column deeper than 20 m, although some divers regularly exceed 50 m (primarily penguins and auks), while 2 species dive in excess of 300 m. The wide-ranging behaviour of seabirds coupled, in many instances, with their substantial body size makes them potentially excellent carriers of sophisticated environmental measuring technology; however, the ethical question of how much the well-being of birds can, and should, be compromised by such an approach needs to be carefully considered.

Description: 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 animal

Description: Movements of animals provisioning offspring by central place foraging extend from short, highly local trips where food is brought back essentially unchanged from its normal condition to extensive interseasonal movement where the offspring are nourished from body reserves built up during the adult's absence from the breeding site. Here, appropriate strategies for maximizing lifetime reproductive success depend on the abundance and location of prey in relation to breeding sites and the energetics and speed of travel of the animal. Magellanic Penguins Spheniscus magellanicus undertake central place movements that are particularly variable during the incubation period; trips may last from a single day to over three weeks depending on colony locality. We reasoned that site-specific variability in prey distribution and abundance is responsible for this. Remote-sensing systems attached to 92 penguins from six different colonies over the species distributional range over the Patagonian Shelf were used to determine space use and foraging patterns in an attempt to understand the observed patterns. Birds in the north and south of the latitudinal range were essentially monophagic, feeding primarily on anchovies Engraulis anchoita and sprats Sprattus fuegensis, respectively, both species that are to be found relatively close to the colonies. Penguins in the center of the distributional range, where these pelagic school fish prey are essentially absent at that time of the year, traveled either north or south, to the same regions utilized by their conspecifics, presumably to exploit the same prey. A simple model is used to clarify patterns and can be used to predict which movement strategy is likely to be best according to colony location. During chick rearing, southerly movement of anchovies and northerly movement of sprats mean that Magellanic Penguins in the center of the distributional range may benefit, although the abundance of these fish is considered to be less than that closer to the Magellanic Penguin range limits. The extensive time involved in the foraging trips during incubation coupled with the postulated poorer prey conditions during the chick-rearing phase may help explain why Magellanic Penguin colony sizes in the center of the range are not elevated.

Description: Body insulation is critically important for diving marine endotherms. However, cormorants have a wettable plumage, which leads to poor insulation. Despite this, these birds are apparently highly successful predators in most aquatic ecosystems. We studied the theoretical influence of water temperature, dive depth, foraging techniques, and prey availability on the energetic costs of diving, prey search time, daily food intake, and survival in foraging, nonbreeding great cormorants (Phalacrocorax carbo). Our model was based on field measurements and on data taken from the literature. Water temperature and dive depth influenced diving costs drastically, with predicted increases of up to 250% and 258% in males and females, respectively. Changes in water temperature and depth conditions may lead to an increase of daily food intake of 500-800 g in males and 440-780 g in females. However, the model predicts that cormorant foraging parameters are most strongly influenced by prey availability, so that even limited reduction in prey density makes birds unable to balance energy needs and may thus limit their influence on prey stocks. We discuss the ramifications of these results with regard to foraging strategies, dispersal, population dynamics, and intraspecific competition in this avian predator and point out the importance of this model species for our understanding of foraging energetics in diving endotherms.

Description: Assessment of food requirements is a key feature in the evaluation of the ecological status of the marine megafauna. However, this remains technically difficult because prey intake by marine top predators occurs mainly under water, out of sight. In this paper, we compare three independent methods currently available for use in quantitative dietary studies: (1) time-energy budget; (2) stomach-temperature measurements; and (3) automatic weighing. To this end, concurrent measurements were performed on Great Cormorants (Phalacrocorax carbo carbo) breeding in Normandy. According to the time-energy budget method, breeding males required 690 g of fish while incubating, 1050 g when rearing small chicks, and 1350 g when rearing large chicks; corresponding values for breeding females were 500, 760, and 970 g. These measurements are similar to estimates derived from automatic weighing data, which gave a mean food intake of 540 and 390 g for incubating males and females, 1150 and 830 g for those tending small chicks, and 1410 and 1010 g for those tending large ones, respectively. Stomach-temperature measurements, which can only be performed for birds raising small chicks, were lower (640 g fish in males and 450 g in females) than those obtained using the other two methods. We compare these results with former estimates obtained at the same study site and for other Great Cormorant subspecies and discuss the relative accuracies of the three techniques. Finally, we stress that better assessment of the ecological status of marine top predators requires further technical improvements and additional investigations outside of the reproductive phase

Description: Albatrosses have among the most remarkable travelling capacities of any extant animal. However, previous studies regarding their movements at sea have mainly focused on breeding birds commuting between the nest site and offshore feeding grounds. In this study, we compare the movement patterns and at-sea activity of breeding and inter-breeding black-browed albatrosses Diomedea melanophris from the Falkland Islands. Data were recorded via global location and activity sensors for 26 incubating birds [during single foraging trips lasting 6.8 d on average) and 6 inter-breeding individuals (during non-stop offshore journeys of 127.5 d on average). Our results showed that foraging black-browed albatrosses utilise vast offshore areas (the average foraging area was 102000 +_ 132 000 km2 by incubating birds and 1552 000 * 970 000 km2 by inter-breeding birds). However, mean forag~ngr ange was similar in both groups (691 * 330 km and 680 t 192 km by incubating and interbreeding birds, respectively) as were their core foraging areas and their at-sea activity patterns. Our results thus indicate that black-browed albatrosses from the Falkland Islands, which represent the largest albatross population world-wide (ca 800 000 individuals), mainly rely on marine resources available within the Patagonian Shelf area. Although this hghly productive continental shelf is the largest of the Southern Hemisphere, rapid development of industrial fisheries currently results in the removal of over 1.4 million tonnes of fish and squid per year in this zone. As our data also show significant spatio-temporal overlap between human and albatross fishing activities within the Patagonian Shelf, we anticipate major detrimental effects on the albatross population in terms of competition for food and additional mortality caused by bird bycatch.