There are indeed reports of brown widows displacing black widows within urban areas in Southern California. It's been observed in some surveys conducted across different counties that the population of brown widows is considerably higher compared to black widows in human-inhabited environments such as residential yards and gardens. Some studies have suggested factors like habitat modification and climatic changes as potential influences on the shift in population dynamics between these species. However, it's crucial to note that the displacement patterns may vary depending on specific locations, and black widow spiders are still commonly encountered in various habitats throughout Southern California.