The disappearance of a Willy Wagtail could be due to several factors. One possibility is natural migration; these birds may move to follow seasonal changes or to find food. Habitat loss or changes in environmental conditions could also lead to their absence in a particular area. Additionally, predation by cats or other animals could impact their population. Human interference, such as urban development or pesticide use, might also play a role in their decline. If you’ve noticed a lack of Willy Wagtails in a specific location, it might be worth your while to monitor the area over time and check if they return, or to consider local wildlife reports for any changes in their habitat.