Provision of supplemental food to female Nazca bobbies Sula granti induces a higher proportion of two-egg clutches at Punta Cevallos, Isla Española (Galápagos Islands), Ecuador

  • Published source details Clifford L.D. & Anderson D.J. (2001) Food limitation explains most clutch size variation in the Nazca booby. Journal of Animal Ecology, 70, 539-545


This study is summarised as evidence for the following.

Action Category

Provide supplementary food for gannets and boobies to increase reproductive success

Action Link
Bird Conservation
  1. Provide supplementary food for gannets and boobies to increase reproductive success

    A randomised, replicated and controlled trial on Isla Española, Galapagos Islands, Ecuador, in the 1997-8 breeding season (Clifford & Anderson 2001) found that female Nazca boobies Sula granti were more likely to produce two-egg clutches if they were fed at least 200 g of mullet Mugil cephalus twice daily, compared with control (unfed) females (92% of 49 fed females produced two eggs vs. 70% of 50 control females). Second eggs were also slightly larger from fed females, compared to controls (68 mm3 for 44 eggs from fed females vs. 66 mm3 for 32 from control females), first-laid eggs were no different between groups. Egg laying date and laying interval were similar between treatments. Females were fed until ten days had passed without laying an egg.


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