Incubation cost was indexed with mass loss of the females during the incubation period and was compared between nests with and without down removal, and between females with enlarged clutches (≥ 7 eggs) and those incubating normal clutches (≤ 6 egg).
Metið var hvort dúntekja hefði áhrif á orkubúskap álegufuglanna með því að athuga mun á léttingu álegukollna á dúnhreiðrum og á heyhreiðrum. Samtímis var rannsakað hvort kollur sem lágu á stórum urptum (≥ 7 egg) eyddu meiri orku en kollur með venjulega urptarstærð (≤ 6 egg).