Floating lovers

Floaters are dispersed individuals who enter the reproductive population when breeding territory or a potential mate become available.

Scientists show that factors affecting the survival of floaters within their settlement areas may directly influence the dynamics of the whole population. They looked at population data for the Spanish imperial eagle, Aquila adalberti, over the last century.

With less than 150 pairs in the whole Iberian Peninsula, this eagle is one of the most threatened raptors in the world. Researchers found that extremely high mortalities of floaters in settlement areas cause a decrease in the number of breeders, due to the increasing difficulty of breeding pair formation and, consequently, a positive density-fecundity relationship in the breeding portion of the population.

The findings support the novel idea that taking floater dynamics within settlement areas into consideration can illuminate inexplicable positive density-dependent patterns in breeding populations.

--LiveScience Staff

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Credit: Penteriani et al.