Fig. 3.

Spring departure dates of immature American redstarts and lilac bud-burst dates at the δD of their first breeding attempt. Lilac bud-burst dates index the start of the growing season at different latitudes and are indicators of phenology in other plant species (25). The correlation between spring departure schedules of immature redstarts and lilac bud-burst dates at the latitude of their first breeding attempt suggests that early departing birds from mangrove (red circles) settled in southerly breeding areas to exploit early plant phenology, whereas later-departing birds from second-growth scrub (blue circles) migrated further north to find suitable conditions.