Dioxin, polychlorinated biphenyls (PCBs), and pesticides impact neural systems in birds due to interference with sexual differentiation. Early endocrine disrupting chemical (EDC) effects may delay maturation and have long-term effects on lifetime reproduction, especially in precocial birds that complete sexual differentiation prior to hatch. Semi-altricial and altricial species appear more resilient to EDC effects and show a gradient in sensitivity, especially in the neuroplastic song system. Embryonic steroid exposure occurs via maternally deposited steroids followed by embryo produced hormones; EDCs potentially affect these developing systems. As such, EDCs can impact lifelong fitness by acting on neural systems that regulate reproduction, metabolism, and behavior.