In this paper we examine the effect of birth order on human capital development in Ecuador. Using family fixed effects models we find positive and persistent birth order effects; earlier-born children stay behind in their human capital development from infancy to adolescence. Turning to potential mechanisms, we find that earlier-born children receive less quality time from their mothers. Additionally, they are breastfed shorter. Poverty plays a key role in explaining these birth order patterns; we observe the largest birth order effects in poor and low-educated families, accompanied with reversed birth order effects in rich and high-educated families.