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| Dickcissel | |
|---|---|
_rick_evans_prairie_w_m_a%2c_hemstead_co%2c_ar_-01_(3)_(42677954221).jpg) | |
| Male in breeding plumage | |
_rick_evans_prairie_w_m_a%2c_hemstead_co%2c_ar_-01_(2)_(42677954611).jpg) | |
| Female | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Passeriformes |
| Family: | Cardinalidae |
| Genus: | Spiza Bonaparte, 1824 |
| Species: | S. americana |
| Binomial name | |
| Spiza americana (Gmelin, 1789) | |
 | |
Breeding Breeding (scarce) Migration Nonbreeding Nonbreeding (scarce) | |
| Synonyms | |
Emberiza townsendi | |
Thedickcissel (Spiza americana) is a smallseed-eatingmigratorybird in thefamilyCardinalidae. It breeds on the prairie grasslands of theMidwestern United States and winters in Central America, northern Colombia, and northern Venezuela. It is theonly member of thegenusSpiza, though some sources list another supposedlyextinct species.
The dickcissel wasformally described in 1789 by German naturalistJohann Friedrich Gmelin under thebinomial nameEmberiza americana.[2] Gmelin based his account on the "black throated bunting" that the Welsh naturalistThomas Pennant had described and illustrated in 1785 in hisArctic Zoology.[3][4] The dickcissel is now the only species placed in the genusSpiza that was introduced in 1824 by French naturalistCharles Lucien Bonaparte.[5][6] The genus nameSpiza is theAncient Greek word for a common type of finch, now assumed to be achaffinch.[7] The species ismonotypic; nosubspecies are recognised.[6]
The dickcissel is part of a group of the Cardinalidae that also includesAmaurospiza,Cyanocompsa,Cyanoloxia, andPasserina.Spiza is the only one among these that lacks bluestructural colors in its plumage. Though the color pattern and habits of the dickcissel make it stand apart from other Cardinalidae, its robust, cone-shaped bill – stouter than inAmerican sparrows ortrue finches, which it somewhat resembles at first glance – gives away its relationships.
A problematic specimen is often discussed under the name ofSpiza townsendi (orSpiza townsendii, the original misspeltspecific name proposed byJohn James Audubon). This individual was collected on May 11, 1833, by Audubon's colleagueJohn Kirk Townsend inNew Garden Township,Chester County, Pennsylvania.[8][9][10] The specimen remains unique and nothing is known about what it represents with certainty; it had thus even been suggested to be anextinct relative. In 2014, Kyle Blaney photographed the bird in Ontario, proving its continuing existence.[11]
It is commonly called "Townsend's dickcissel" (or "Townsend's bunting", "Townsend's finch"[12]) in reference to the collector whom the scientific name honors. Rather than a distinct species or subspecies, it is (as certainly as this can be said in absence of direct proof) a colorvariant. Comparing the birds, it is immediately obvious that the yellowlipochromepigments are entirely absent in "Townsend's dickcissel". The specimen hasfoxed today, giving it an altogether beige hue, but when originally shot, the olive areas of the head were grey as the cheeks, and the yellow and buff on face and underside was pure white. The brown wings and tail were rufous, due to thepheomelanins not being tinged by lipochromes.
Thus, this bird is very likely certainly the result of a simple genetic change, perhaps just a singlepoint mutation, affecting some part of thecarotinoidmetabolism – essentially the same thing that happens inalbinism, but in a differentmetabolic pathway. Though the bird seemed to be healthy and had survived to maturity when it found its untimely end through Townsend's gun, no other such specimens have been documented before, nor ever since. Albinism and other pigment aberrations are not infrequently seen in birds, and the lack of further specimens is somewhat puzzling in that respect.
No specific details are known about the dickcissel's lipochrome metabolism; it may be more fine-tuned than in other birds, so that most mutations therein will be lethal and Audubon's bird was simply one of the very few individuals that survived. In wild birds, varying from species to species, some color aberrations are less frequently seen than others, and in captive birds such ascanaries, some color mutations have only arisen a handful of times at most during several centuries of dedicated breeding and screening for novel color variants (see alsoBudgerigar colour genetics). While only a completemolecular biological study of the dickcissel's metabolism and the specimen'sancient DNA stands any reasonable chance to resolve the question with certainty, the hypothesis of an extremely uncommon color mutation is plausible, and such phenomena certainly occur in otherPasseroidea.
Alternatively, the bird was considered ahybrid, but the present state of knowledge of the dickcissel's relations makes this not very plausible; a number of species exist with whichSpiza could conceivably produce hybrids, such asPasserina, but the lack of even the slightest hint of blue structural colors in Townsend's specimen and it moreover being not different from a dickcissel inhabitus makes the hybrid theory suspect. Regardless, Townsend observed the bird making vocalizations reminiscent more of anindigo bunting (Passerina cyanea), and by comparingmitochondrial andnuclear DNA sequences of the specimen with those of the dickcissel, the indigo bunting, and perhaps otherPasserina, the hybridization hypothesis should be far more easy to prove or reject than a color aberration. On the other hand, not enough is known on whether dickcissels pick up their characteristic vocalizations from conspecific males or whether they are innate, thus no firm conclusion regarding Townsend's observations has been made.
Their length is 5.5–6.3 in (140–160 mm), wingspan is 9.8–10.2 in (250–260 mm), and weight is0.9–1.4 oz (26–40 g).[13] Dickcissels have a large, palebill, a yellow line over the eyes, brownish upperparts with black streaks on the back, dark wings, a rust patch on the shoulders, and light underparts. Adult males have a black throat patch, a yellow breast, and grey cheeks and crown. This head and breast pattern is especially brilliant in the breeding plumage, making it resemble aneastern meadowlark. Females and juveniles are brownish on the cheeks and crown, and are somewhat similar in appearance tohouse sparrows; they have streaked flanks.
In flight, they make a low, "electric", buzzingfpppt. From an open perch in a field, this bird's song is a sharpdick dick followed by a buzzedcissel, also transcribed asskee-dlees chis chis chis ordick dick ciss ciss ciss.[14]
Their breedinghabitat is fields inmidwestern North America. Following the breeding season the speciesmigrates in large flocks to southern Mexico, Central America, and northern South America. They may occur as vagrants well outside of their normal range. From 1966 to 2015 the dickcissel experienced a greater than 1.5% population reduction in the northern part of its breeding range and throughout theMidwestern United States.[15]
The birds migrate to their breeding range rather late, with the first arriving only in May, with most birds only arriving in early June.[16][17] They nest near the ground in dense grasses or small shrubs, or up to 3–4 ft (91–122 cm) high in bushes and trees. Males may have up to six mates, with most attracting only one or two, and several failing to attract any mates at all. Yet if such "bachelors" survive until the next summer, they will get another try to attract females, as the partners only stay together for raising one brood. Dickcissels are thus among the fewsongbirds that are trulypolygynous. When they leave for winter quarters by early August or so,[17] what little pair bond existed during the summer is broken up.
Dickcissels forage on the ground or in fields. They mainly eatinsects andseeds. Outside of the nesting season, they usually feed in flocks. They are considered a pest by farmers in some regions because flocks can consume large quantities of cultivatedgrains.
Dickcissel populations frequently fluctuate in numbers, even to the extent that their range changes notably. In the early 19th century, dickcissels expanded eastward, establishing a population inNew England and themid-Atlantic states that disappeared around the end of the century. Both appearance and disappearance were probably related to changes in land use.[18]
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