Mallorca shearwaters follow their mothers’ egg timing

At Sa Dragonera Natural Park off Mallorca, a 22-year study finds that daughters of early-laying shearwaters tend to breed early too. That matters: females that lay earlier have better breeding success and higher survival rates. Researchers tracked hundreds of Scopoli’s shearwaters, a migratory seabird, for the study reported on 12 November 2026.

Winter weather shifts the calendar

The birds breed in the Mediterranean and spend winter in the Atlantic, mainly off West Africa. To examine how conditions affect them, researchers compared their breeding dates with the North Atlantic Oscillation, an index of weather and ocean conditions. Its positive winter phases are linked to less favourable breeding conditions for the shearwaters.

Winter conditions can affect nutrients in the western Mediterranean and, in turn, the prey available to the birds. Females adjust when they start breeding from year to year, but those that lay early usually remain early compared with others in the colony. Scientists call that ability to adjust phenotypic plasticity.

An early start brings an advantage

In 142 cases, the researchers found that daughters of early-laying mothers also bred earlier than the colony average. The data cannot show whether genes, maternal influences or shared surroundings explain the link.

The advantage of breeding early is clearest during birds’ first attempts. Less experienced shearwaters are also more sensitive to poor conditions. Study author Sofia Bolumar says it remains unclear whether their ability to adjust will keep pace with Mediterranean warming.

Topics: Nature & wildlife

Source: Europa Press / Mallorca.com