Black-crowned Night-Herons (BCNH; Nycticorax nycticorax) increasingly colonize urban areas, demonstrating they consider the value of such habitat to outweigh the risks. However it is unclear if cities support reproductively successful populations of BCNH. To begin to address this question, I evaluated if a park in Chicago, Illinois, provided suitable breeding habitat or was an ecological trap for a colony of approximately 400 BCNH. Nest densities were 217 nests/ha in 2010 and 315 nests/ha in 2011, which were higher than nest densities observed in North American BCNH colonies in natural habitats. Ratios of young to active nests were 1.22 in 2010 and 0.76 in 2011, similar to ratios observed in nearby BCNH colonies. Within the park BCNH selected between two neighboring habitat patches. Logistic regression was used to predict habitat patch selection as a function of colony size and year. In the model the probability of selecting a larger, more exposed habitat patch versus a smaller, more secluded habitat patch, increased with colony size. This trend in habitat patch selection demonstrated behavioral flexibility which may have facilitated successful colonization of a human-modified landscape. The findings support the conclusion that in 2010 and 2011, an urban park in Chicago supported a locally endangered BCNH population and was not an ecological trap.