Parental body mass changes during the nesting stage in two Lark species in a semi-arid habitat

Parental body mass changes during the nesting period were analysed for Thekla Larks, Galerida theklae, and Lesser Short-toed Larks, Calandrella rufescens. Body mass of female Thekla Larks declines from the start of incubation until the chicks fledge; laying date, interpreted as the number of renesting attempts, also has a negative effect. Body mass of female Lesser Short-toed Larks was not related to any of these variables, except laying date during the incubation stage. Male Thekla Larks lost body mass during the nestling phase. All female Thekla Larks which were recaptured lost body mass during incubation and female Lesser Short-toed Larks lost body mass during the post-hatching period. Body mass losses throughout the whole nesting period were 14% and 16% for adult female Thekla Larks and Lesser Short-toed Larks, respectively, and 2.5% and 2.6%, respectively, for the males of these two species during the nestling phase. Body mass declines in the two species seem to be related to the number of clutches laid and not to clutch size, but the two show different patterns of body mass variation, which are also different from the only other lark of desert environments in which body mass when nesting has been studied to date.