Home About us Contact
|
Home About us Contact | ||
|
|
||
Macaroni Penguins (macaroni + penguin)
Selected AbstractsEstimating food consumption of marine predators: Antarctic fur seals and macaroni penguinsJOURNAL OF APPLIED ECOLOGY, Issue 1 2002I.L. Boyd Summary 1Estimating food consumption is central to defining the ecological role of marine predators. This study developed an algorithm for synthesizing information about physiology, metabolism, growth, diet, life history and the activity budgets of marine predators to estimate population energy requirements and food consumption. 2Two species of marine predators (Antarctic fur seal Arctocephalus gazella and macaroni penguin Eudyptes chrsolophus) that feed on krill in the Southern Ocean were used as examples to test the algorithm. A sensitivity analysis showed that estimates of prey consumed were most sensitive to uncertainty in some demographic variables, particularly the annual survival rate and total offspring production. Uncertainty in the measurement of metabolic rate led to a positive bias in the mean amount of food consumed. Uncertainty in most other variables had little influence on the estimated food consumed. 3Assuming a diet mainly of krill Euphausia superba, annual food consumption by Antarctic fur seals and macaroni penguins at the island of South Georgia was 3·84 [coefficient of variation (CV) = 0·11] and 8·08 (CV = 0·23) million tonnes, respectively. This was equivalent to a total annual carbon consumption of 0·35 (CV = 0·11) and 0·72 (CV = 0·23) G tonnes year,1. Carbon expired as CO2 was 0·26 (CV = 0·06) and 0·65 (CV = 0·19) G tonnes year,1 for fur seals and macaroni penguins, respectively. The per capita food consumption varied depending upon sex and age but, overall, this was 1·7 (CV = 0·22) tonnes year,1 for Antarctic fur seals and 0·45 (CV = 0·22) tonnes year,1 for macaroni penguins. 4The algorithm showed that the seasonal demand for food peaked in both species in the second half of the breeding season and, for macaroni penguins, there was a second peak immediately after moult. Minimum food demand occurred in both species during the first half of the breeding season. 5As both Antarctic fur seals and macaroni penguins compete for krill with a commercial fishery, these results provide an insight into the seasons and stages of the life cycle in which competition is likely to be greatest. [source] The double vocal signature of crested penguins: is the identity coding system of rockhopper penguins Eudyptes chrysocome due to phylogeny or ecology?JOURNAL OF AVIAN BIOLOGY, Issue 5 2005Amanda Searby Parent-offspring recognition systems are used in bird colonies to avoid misdirected parental care. In penguins, where the risk of confusion is particularly high, recognition is achieved by acoustic signals that constitute highly efficient vocal signatures. Comparisons between species from the Pygoscelis and Aptenodytes genera have revealed interspecific differences on the encoding of information within the signatures which correlate with the presence/absence of nests in the colonies. However a recent study of individual recognition in macaroni penguins Eudyptes chrysolophus revealed diversity within nest-building species. This paper investigates whether the original and intermediate signature system found in macaroni penguins is shared by another species of Eudyptes, the rockhopper penguin E. chrysocome. Vocal signatures of rockhopper penguins were analysed and compared to macaroni penguins'. We used a methodology derived from the theory of information to determine which parameters of the call were likely to encode individual identity. Playbacks of modified calls in the field complemented the analyses, and parent-chick reunions were compared between the two species. Our results reveal a similar double signature system within the Eudyptes genus, which integrates information simultaneously from the temporal and spectral domains. This double encoding is made through the tempo given by the successive syllables of the call and the harmonic content of the call. While it confirms the hypothesis that signatures are simpler in nest-building species, this result reveals differences in the efficacies of signatures within this category. This suggests that other parameters such as the mean distance recognition should be considered to account for the differences in the encoding of the vocal signatures and in their resulting efficacies. [source] | ||||||||||