The palm warbler is regarded as the most terrestrial species in its genus (4), typically walking along the ground and continuously wagging its tail as it does so (2) (4). Although this species does not form flocks, individuals are often seen feeding close together (3).
The ground-feeding palm warbler’s diet consists mostly of insects (2) (3) (4) and other arthropods (2), including grasshoppers, beetles and flies (4). These prey items are either picked off the ground or from shrubs, or are caught during short fly-catching sallies (2) (3) (4). In the winter, the palm warbler is known to supplement its diet with seeds, berries and even nectar (2) (3) (4), particularly that of the century plant (Agave braceacea) (2) (4).
The palm warbler is a territorial species during the breeding season, with males singing to announce their presence and declare ownership of a territory. This species is primarily monogamous, and pairs tend to form shortly after the palm warbler arrives on its breeding grounds (4). The breeding season is variable depending on the location, but typically occurs between May and July (2) (4).
Usually found nestled in Sphagnum moss on a peat bog, well hidden beneath a small conifer, the nest of the palm warbler is a cup-shaped structure formed from weed stalks, grass, moss and strips of bark (2) (3) (4). The nest is lined with fine grass, feathers (2) (3) (4), and sometimes deer or horse hair (4).
The female palm warbler lays a clutch of four or five eggs (2) (3) (4), which are white to creamy white and speckled with reddish brown, lavender or lilac spots (4). It is thought that only the female incubates the eggs (4), for a period of around 12 days (2) (3). The male palm warbler feeds the female during incubation, and helps the female to feed the young once the eggs hatch. Young palm warblers leave the nest at between 8 and 12 days of age, and stay with the adult birds for a further 8 days after fledging. The palm warbler is known to only produce one brood per breeding season, although this species may nest a second time if the first clutch fails (4).
The palm warbler is medium- to long-distance migrant (2) (4), and is believed to migrate earlier in the spring and later in the autumn than most other wood-warbler species (4). It typically leaves its breeding grounds from early September (2), and migrates at night in small flocks, often in association with other birds such as sparrows and other warbler species (4).