Fig. 3.

Relative egg mass (corrected for adult mass) and average egg temperature over 24-h periods. Relative egg mass is greater in species where parental inattentiveness causes lower egg temperatures based on study of 37 passerine species in tropical Venezuela, subtropical Argentina, and north temperate Arizona. Open symbols are cavity-nesting species and show an interacting effect where their larger clutches are associated with relatively smaller eggs (Fig. 2).