Reproductive success of the endangered whooping crane (Grus americana) maintained ex situ is suboptimal. The main goals of this multidisciplinary investigation are to advance the understanding of whooping crane reproduction and identify potential causes of poor reproductive success in a captive colony. The specific objectives include (Study 1) determining overall seminal characteristics and examine the influences of inbreeding, age, and stages of breeding season on seminal quality in captive birds and (Study 2) utilizing non-invasive endocrine monitoring to longitudinally assess gonadal and adrenal steroids of bird pairs with various reproductive outcomes and evaluating the relationship between hormones and crane behaviors. Our findings demonstrate that (1) there is no relationship between inbreeding coefficient or age and seminal quality of the whooping crane and (2) stage of breeding season impacted seminal output and characteristics. Overall estradiol concentrations and reproductive behaviors, but not glucocorticoid levels, were also key determinants to successful reproductive output.