Yellow warbler
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, as well as northern South America.
Taxonomy
The yellow warbler was formally described in 1766 by the Swedish naturalist Carl Linnaeus in the twelfth edition of his Systema Naturae under the binomial name Motacilla petechia. The specific epithet petechia is from the Italian word petecchia "a small red spot on the skin". Linnaeus based his account on the "yellow-red pole" that had been described and illustrated in 1758 by the English naturalist George Edwards in his book Gleanings of Natural History. Edwards had obtained a specimen from the midwife Sidney Kennon. Edwards was unsure of the provenance of the specimen but in 1935 the Austrian ornithologist Carl Eduard Hellmayr designated the island of Barbados. The yellow warbler is now placed in the genus Setophaga that was introduced by the English naturalist William Swainson in 1827. The genus name Setophaga combines the Ancient Greek σης/sēs, σητος/sētos meaning "moth" with -φαγος/-phagos meaning "-eating".Description
Other than in male breeding plumage and body size, all warbler subspecies are very similar. Winter, female and immature birds all have similarly greenish-yellow uppersides and are a duller yellow below. Young males soon acquire breast and, where appropriate, head coloration. Females are somewhat duller, most notably on the head. In all, the remiges and rectrices are blackish olive with yellow edges, sometimes appearing as an indistinct wing-band on the former. The eyes and the short thin beak are dark, while the feet are lighter or darker olive-buff.The 35 subspecies of S. petechia can be divided into three main groups according to the males' head color in the breeding season. Each of these groups is sometimes considered a separate species, or the aestiva group is considered a species different from S. petechia ; the latter option is the one currently accepted by the International Ornithological Congress World Bird List.
Depending on subspecies, the yellow warbler may be between long, with a wingspan from. They weigh, varying between subspecies and whether on migration or not, globally averaging about but only in most breeding adults of the United States populations. Among standard measurements throughout the subspecies, the wing chord is, the tail is, the bill is and the tarsus is. The summer males of this species are generally the yellowest warblers wherever they occur. They are brilliant yellow below and greenish-golden above. There are usually a few wide, somewhat washed-out rusty-red streaks on the breast and flanks. These markings are the reason for the scientific name petechia, which roughly translates to "liver spotted". The subspecies in this group mostly vary in brightness and size according to Bergmann's and Gloger's Rule.
The golden warbler is generally resident in the mangrove swamps of the West Indies. Local seasonal migrations may occur. On the Cayman Islands for example, S. p. eoa was found to be "decidedly scarce" on Grand Cayman and apparently absent from Cayman Brac in November 1979, while it had been a "very common" breeder in the group some ten years before, and not frequently seen in the winters of 1972/1973; apparently, the birds disperse elsewhere outside the breeding season. The Cuban golden warbler barely reached the Florida Keys where it was first noted in 1941, and by the mid-20th century a breeding population was resident. Though individual birds may stray farther north, their distribution is restricted by the absence of mangrove habitat.
They are generally smallish, usually weighing about or less and sometimes as little as. The summer males differ from those of the yellow warbler in that they have a rufous crown, hood or mask. The races in this group vary in the extent and hue of the head patch.
The mangrove warbler tends to be larger than other yellow warbler subspecies groups, averaging in length and in weight. It is resident in the mangrove swamps of coastal Middle America and northern South America; S. p. aureola is found on the oceanic Galápagos Islands. The summer males differ from those of the yellow warbler in having a rufous hood or crown. The races in this group vary in the extent and hue of the hood, overlapping extensively with the golden warbler group in this character.
The American yellow warbler breeds in the whole of temperate North America as far south as central Mexico in open, often wet, woods or shrub. It is migratory, wintering in Central and South America. They are very rare vagrants to western Europe and Scandinavia
Vocalizations
The song is a musical strophe that can be rendered sweet sweet sweet, I'm so sweet, although it varies considerably between populations. The call is a soft or harder chip or ship. This is particularly frequently given by females after a male has finished his song. In territorial defense, they give hissing calls, while seet seems to be a kind of specialized cowbird alert. Other calls are given in communication between pair-members, neighbors, or by young begging for food. These birds also communicate with postures and perhaps with touch.Behaviour and ecology
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. 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.
Roughly 60% of their diet is caterpillars. They also consume wasps, mayflies, moths, mosquitoes, beetles, damselflies, treehoppers, other insects, insect larvae, and spiders. 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 . Caterpillars are the staple food for nestlings, with some – e.g. those of geometer moths – preferred over others.
The predators of yellow and mangrove warblers are those typical of such smallish tree-nesting passerines, such as snakes, foxes, birds of prey, and many others. The odds of an adult American yellow warbler surviving 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 and common garter snake, are significant nest predators, taking nestlings and fledglings as well as sick or distracted adults. Likewise, corvids such as the American crow and blue jay, and large climbing rodents, notably the American red squirrel also attack nests in this manner. Carnivores including the striped skunk, long-tailed weasel, common raccoon, red fox, 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 and Cooper's hawk, and the sharp-shinned hawk. Other avian predators of adults have included peregrine falcons and merlins. Owls such as great horned owls and eastern screech owls have been known to assault yellow warblers of all ages at 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, with about 40% of all nests suffering attempted or successful parasitism. By contrast, the tropical populations are less frequent hosts to the shiny cowbird, with only 10% of nests affected. This may be due to the slightly larger size of shiny cowbirds, which are less likely to survive being fed by the much smaller warbler, compared to brown-headed cowbirds. The yellow warbler is one of the few passerine proven to be able to recognize the presence of cowbird eggs in its nest. Upon recognizing one the warbler will often smother it with a new layer of nesting material. It will usually not try to save any of its own eggs that have already been laid, but produce a replacement clutch. Sometimes, the parents desert a parasitized nest altogether and build a new one. Unlike some cuckoos, cowbird nestlings will not actively kill the nestlings of the host bird; mixed broods of Setophaga and Molothrus may fledge successfully. However, success of fledging in yellow warbler nests is usually decreased by the parasitism of cowbirds due to the pressures of raising a much larger bird.
Other than predation, causes of mortality are not well known. The maximum recorded ages of wild yellow warblers are around 10 years. A wintering American yellow warbler examined near Turbo, Colombia was not infected with blood parasites, unlike other species in the study. It is unclear whether this significant, but wintering birds in that region generally lacked such parasites.