Unlocking elementary secrets of seabirds

Monday, 20 February 2023

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Unlocking elementary secrets of seabirds

Albatrosses travel widely for nutrients as well as food

BirdLife Australia has funded a ground-breaking study which is unlocking some of the secrets of seabirds’ private lives. While the ecology of many different seabirds is well known at their breeding colonies, their lives at sea are much less clearly understood, and until now, even basic details about why they occur where they occur have been somewhat shrouded in mystery.

The study, undertaken by the University of South Australia and the CSIRO, has shed a little light on the movements and distribution at sea of Australia’s albatrosses, some of which may circumnavigate the globe multiple times within a year.

Part of the mystery about their travels stems from the fact that many of their food items — particularly krill, fish and squid — are often readily available in the waters surrounding their breeding colonies, and yet various species of seabirds travel many thousands of kilometres, spending months at a time out at sea.

The study has found that these journeys may not simply be related to foraging and resulting energy expenditure budgets, but are driven (at least in part) by the need for certain nutrients and trace elements in their diet.

The scientists analysed the feathers of 15 species of seabirds, all collected from the Tasman Sea and other parts of the western South Pacific Ocean — considered a global biodiversity hotspot. The connection between ocean nutrient hotspots and abundance of wide-ranging marine species has long been known, but it has often been attributed only to these sites’ concentrations of food items, but the analysis suggested that something else might be at play.

Their analysis revealed that the feathers had characteristic micronutrient element ‘fingerprints’ that did not match the availability of these nutrients at the sites where the feathers were collected.

This evidence suggested that certain nutrients are available in different concentrations in the sea water of different ocean basins. Thus, it may be this aspect of their ecology and metabolic requirements, as well as the productivity of different parts of the ocean, that are drivers of the birds’ movements and their distribution when at sea in the world’s southern oceans.

The link between the presence of albatrosses and other seabirds and the distribution of nutrient hotspots in oceanic waters is an emerging key that is important in unlocking our understanding what makes the world’s seabirds tick, as well as providing valuable information for those decisionmakers whose responsibilities include seabird conservation and protection. It is especially important in the face of warming ocean waters as a consequence of accelerating climate change.