Birds of the Week # 37

Yellow-rumped Warble

The Yellow-rumped Warbler (Setophaga coronata) is a regular North American bird species that can be commonly observed all across the continent. The yellow-rumped warbler’s migratory behaviors vary greatly across different groups and subspecies. Some individuals in Central America, such as in Mexico and Guatemala, migrate only limitedly or do not migrate at all; while individuals in the northern parts of the continent may either choose to migrate all the way towards Central America or winter near their breeding area along the Pacific Coast of the U.S. The species’s migratory behaviors are generally nocturnal, as individuals tend to travel at night; accordingly, during the yellow-rumped warbler’s migration in spring, it often relies on skylight polarization as a way to navigate and orient at dusk. The general direction of its migratory route maintains southwards during winter, as more individuals are present in Central America and southern parts of North America during the season, while less are observed in the north. Every year, fall migration usually takes place from September to November, spring migration from April to May, and the species known to depart from its winter habitats from March to April. Research shows that before migration, the yellow-rumped warbler intentionally gains weight and accrues more fat in its body: as a preparation for this energy-intensive activity, it consumes more food than other times for the purpose of increasing net energy intake from feeding, along with a refined diet that gives priority to food that supplies more energy.

Ruby-crowned Kinglet

The Ruby-crowned Kinglet (Corthylio calendula) is a very small passerine bird found throughout North America. It is a member of the kinglet family. The bird has olive-green plumage with two white wing bars and a white eye-ring. The ruby-crowned kinglet is a very small bird, being 9 to 11 cm (3.5 to 4.3 in) long, having a wingspan of 16 to 18 cm (6.3 to 7.1 in), and weighing 5 to 10 g (0.2 to 0.4 oz). It has gray-green upper-parts and olive-buff underparts. It has two white wingbars and a broken white eye ring. The wingbar on the greater secondary coverts (closer to the wing-tip) is wider, and is next to a dark band. The kinglet has a relatively plain face and head, although the male has a scarlet-red crown patch, which is usually concealed by the surrounding feathers. The crown patch is rarely orange, yellow, or not present. Females are identical to males (except for the crown). Immature birds are similar to adult females, since young males lack a crown patch. The kinglet usually moves along branches or through foliage with short hops, and flies with bursts of rapid wing beats. It is constantly active, and is easily recognized by its characteristic wing-flicking. Its flight has been described as “swift, jerky, and erratic.

© HJ Ruiz – Avian101

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