Relaying propensity and characteristics of replacement clutches of Leach’s Storm-Petrels ( Oceanodromaleucorhoa)

Animals with low fecundity, such as seabirds, invest heavily into one or a few eggs per breeding attempt. The loss of these eggs can mean that individuals abandon breeding or invest in a replacement clutch. However, the ability of females to replace clutches may be costly and so replacement clutches may be delayed and they may differ in nutrient content. Replacement clutches are rarely documented conclusively in storm-petrels, and most avian replacement clutches are smaller and differ in composition from original eggs. We removed eggs from Leach’s Storm-Petrel (Oceanodroma leucorhoa (Vieillot, 1818)) nests on Gull Island, Witless Bay, Newfoundland and Labrador, Canada, and monitored nest sites for replacement clutches. Leach’s Storm-Petrels use locally acquired nutrients to lay a single egg that weighs 20% of a female’s body mass. Nearly 70% of pairs (17/26) produced a replacement egg after 22 days and two pairs produced a third egg after a further 21 days. Replacement eggs were nearly identical to original clutches, except for small decreases in length (2%) and volume (3%). We found that Leach’s Storm-Petrels were able to acquire sufficient nutrients to produce a second (and in two cases, a third) egg, likely from endogenous nutrients, but delays of 3–6 weeks in breeding may have detrimental effects on fledging success and offspring survival.