page_title: American yellow warbler
section_title: Ecology
hierarchical_section_title: American yellow warbler / Ecology
caption_attribution_description: English: Yellow Warbler Dendroica aestiva (syn. D. petechia aestiva) attends to the nest, Yukon Flats National Wildlife Refuge Attempt at color correction.
context_page_description: The yellow warbler is a New World warbler species. Yellow warblers are the most widespread species in the diverse genus Setophaga, breeding in almost the whole of North America, the Caribbean, and down to northern South America.
context_section_description: American yellow warblers breed in most of North America from the tundra southwards, except for the far Southwest and the Gulf of Mexico coast. American yellow warblers winter to the south of their breeding range, from southern California to the Amazon region, Bolivia and Peru. The mangrove and golden warblers occur to the south of it, to the northern reaches of the Andes.
  American yellow warblers arrive in their breeding range in late spring – generally about April/May – and move to winter quarters again starting as early as July, as soon as the young are fledged. Most, however, stay a bit longer; by the end of August, the bulk of the northern populations has moved south, though some may linger almost until fall. At least in northern Ohio, yellow warblers do not linger, leaving as they did 100 years ago.
  The breeding habitat of American yellow warblers is typically riparian or otherwise moist land with ample growth of small trees, in particular willows (Salix). The other groups, as well as wintering birds, chiefly inhabit mangrove swamps and similar dense woody growth. Less preferred habitat are shrubland, farmlands and forest edges. In particular American yellow warblers will come to suburban or less densely settled areas, orchards and parks, and may well breed there. Outside the breeding season, these warblers are usually encountered in small groups, but while breeding they are fiercely territorial and will try to chase away any conspecific intruder that comes along.
  These birds feed mainly on arthropods, in particular insects. They acquire prey by gleaning in shrubs and on tree branches, and by hawking prey that tries to fly away. Other invertebrates and some berries and similar small juicy fruits are also eaten, the latter especially by American yellow warblers in their winter quarters. The yellow warbler is one of several insectivorous bird species that reduce the number of coffee berry borer beetles in Costa Rica coffee plantations by 50%. Caterpillars are the staple food for nestlings, with some – e.g. those of geometer moths (Geometridae) – preferred over others.
  The predators of yellow and mangrove warblers are those – snakes, foxes, birds of prey, and many others – typical of such smallish tree-nesting passerines. The odds of an adult American yellow warbler to survive from one year to the next are on average 50%; in the southern populations, by contrast, about two-thirds of the adults survive each year. Conversely, less than one American yellow warbler nest in three on average suffers from predation in one way or another, while two out of three mangrove and golden warbler nests are affected.
  Snakes, including the blue racer (Coluber constrictor foxii) and common garter snake (Thamnophis sirtalis), are significant nest predators, taking nestlings and fledglings as well as sick or distracted adults. Likewise corvids such as the American crow (Corvus brachyrhynchos) and blue jay (Cyanocitta cristata), and large climbing rodents, notably the American red squirrel (Tamiasciurus hudsonicus). Carnivores, in particular members of the Musteloidea, including the striped skunk (Mephitis mephitis), long-tailed weasel (Mustela frenata) and common raccoon (Procyon lotor); the red fox (Vulpes vulpes); and domestic or feral cats, are similarly opportunistic predators. All these pose little threat to the nimble, non-nesting adults, which are taken by certain smallish and agile birds such as the American kestrel (Falco sparverius) and Cooper's hawk (Accipiter cooperii), and the sharp-shinned hawk (A. striatus). Other avian predators of adults have included peregrine falcons (Falco peregrinus) and merlins (Falco columbarius). Owls such as great horned owls (Bubo virginianus) and eastern screech owls (Megascops asio) have been known to assault yellow warblers of all ages during night.
  These New World warblers seem to mob predators only rarely. An exception are cowbirds, which are significant brood parasites. The yellow warbler is a regular host of the brown-headed cowbird (Molothrus ater), with about 40% of all nests suffering at
caption: Female yellow warbler attending nestlings, Yukon Flats National Wildlife Refuge, Alaska (USA)
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