Summer residents. The average dates of arrival and departure are inserted between the earliest spring and the latest autumn records. In the case of birds which occasionally Spend the winter (as the Catbird) the word winter' is added after the average dates, and early and late dates are given only when there is no doubt that they relate to individual birds which had just arrived from the South or were about to return to it. Transient visitors. The average spring dates of arrival and departure are inserted between the earliest and the latest spring records. The same plan is used with the autumn dates. In the case of birds which occasionally pass the summer (as the Solitary Vireo) the word 'summer' is added after the average spring dates. In the same way, if a bird occasionally passes the winter (as the Rusty Blackbird), the word 'winter' is added after the average autumn dates. In all these cases early and late spring and autumn dates are used only when they certainly relate to migrating birds.