A study of wandering albatrosses has shown that some are breeding earlier in the season compared with 30 years ago.
University scientists took part in a study of the breeding habits of the iconic seabird on the sub-Antarctic island of South Georgia.
They found that some birds are now laying their eggs earlier, and the laying date for the population is an average of 2.2 days earlier than before.
The researchers say the reasons for this change within the birds - among the largest on Earth - are unclear.
Every year we can determine when the birds return to the island after migration, and the exact day they lay their egg.
The researchers studied more than 30 years' worth of data from birds located near the British Antarctic Survey’s research station on Bird Island, South Georgia.
Nest sites were monitored daily during the pre-laying, laying, hatching and fledging periods to document breeding patterns.
Numbers of wandering albatrosses on South Georgia have been steadily declining largely because the birds swallow baited hooks on longlines set by fishing vessels, and are dragged under and drown.
Despite a recent increase in breeding success over the past 20 years, the number of birds at Bird Island has fallen by more than 50% since the 1960s, from 1700 to only 800 breeding pairs.
Scientists say the work is important for understanding more about the behaviour of these charismatic and threatened birds.
In the Indian Ocean, an increase in the intensity of westerly winds has resulted in a shift in feeding distribution of wandering albatrosses.
Researchers say it is possible that earlier breeding in some females at South Georgia is a consequence of environmental change, but they are not sure if this is related to weather, a change in oceanographic conditions or food availability to which only some birds are responding.
This research, a collaboration between the University of Edinburgh and British Antarctic Survey, was funded by the Natural Environment Research Council and published in the journal Oikos.
Our results are surprising. We knew that some birds were laying earlier – those who were older or had recently changed partner - but now we see that those which haven’t bred successfully in the past are also laying earlier, and these birds are effectively driving this trend in earlier laying.