In biparental bird species, the contribution of the sexes to parental care can be observed. Males often provide parental care at different  stages of  reproduction. We studied parental effort in small passerine altricial bird species. We observed the rate of feeding and time of heating by female and male of the reed bunting Emberiza schoeniclus. The observations were carried out during two breeding seasons in 2013 and 2014 year on diverse, overgrowing, not used fish-ponds in Liwiec river valley (E Poland). In the first days after hatching both parents beside of feeding heated nestlings in the nest. Generally parental effort increased with age of nestlings, but only female increased significantly their feeding frequency as the nestlings became older. In average females fed significantly more often than males. The heating time not differed significantly between both parents. The frequency of nestling-feeding depended on age of nestlings but not on their number. Sex differences in parental effort have been observed in a many of biparental-care bird species. In the reed bunting it may be related differences in roles the parents play at different stages of brood development and high level of extra-pair paternity.