Variable seedeater

Abstract: —Detailed examination of variation in Sporophila americana in Panama necessitates major changes in the stated ranges and nomenclature of the subspecies found there. The name hicksii (Lawrence, 1865) is revived for white-throated black and white birds on the Pacific coast of Panama from Veraguas east through Darien (skipping the Canal Zone), the Caribbean coast in San Bias, and south in western Colombia to Valle. The currently recognized name chocoana (Meyer de Schauensee, 1950) becomes a synonym of hicksii. It is suggested that the type locality of hicksii should be Buenaventura, Colombia, instead of Panama. Black-throated black and white birds from the Pacific slope of Costa Rica and Chiriqui may now be known under the resurrected name hoffmanni Cabanis, 1861. The nearly black subspecies corvina (Sclater, 1859) extends along the western Caribbean coast of Panama and in the Canal Zone intergrades with hicksii to form a hybrid zone in which no pure parental types occur. The long-used but dubiously applicable name "aurita" (Bonaparte, 1850) is tentatively applied to these intergrades and the specimens are analyzed by the use of a hybrid index. As its name implies, the Variable Seedeater, Sporophila americana, has been regarded as being so variable in the adult male plumage, particularly in Panama, as to defy interpretation in terms of normal geographic variation. This idea became so fixed in the earlier literature that contrary information was often ignored. No recent attempts have been made to examine series of specimens from Panama to elucidate distributional patterns there. By current taxonomic practices there are three subspecies of Sporophila americana recognized in Panama: S. a. corvina, a nearly all black form found on the Carribean slope of western Panama north to Mexico; S. a. aurita, a supposedly extremely variable black and white form found on the Pacific slope of Costa Rica and Panama to the Canal Zone and on both slopes east of the Canal to Darien, where it is supposedly replaced by a more constant white-throated form, S. a. chocoana, inhabiting easternmost Panama and Pacific Colombia south to the Rio Dagua. The development of this classification may be traced through the publications of Sclater (1871), Chapman VOLUME 94, NUMBER 2 381 %) -holfmonil x ^cksil intergrades X -"Qufil^" (hybrid cwving A M'Cksir) Fig. I. Distribution of the forms of Sporophila americana in Panama, based on specimens examined in this study. (1926), Hellmayr (1938), Meyer de Schauensee (1950, 1952) and Eisenmann (1957). Not all of the observations below are entirely original, but their significance has not hitherto been appreciated. I shall not attempt to treat the history of each conclusion, as this may be found in the references just cited. The classification I shall propose differs considerably from that above. For this reason and because the nomenclatural changes I shall propose are rather intricate, I shall begin by presenting my conclusions first and documenting them beyond. The revised distribution and nomenclature of S. americana in Panama is shown in Fig. 1. No change in status is required for the black populations from the western Caribbean coast, S. a. corvina. Much of the rest of the isthmus is occupied by a black and white subspecies, with a white rump and throat, which occurs in most of Panama east of the Canal Zone and west of the Canal Zone on the Pacific slope to central Veraguas. The name hicksii is resurrected for this subspecies, with chocoana falling into synonymy. A similar subspecies, but with a black throat, is found from western Veraguas, including Isla Coiba, west along the Pacific slope through Costa Rica. The name hoffmanni is revived for this form. The only birds showing great variability are restricted to the area of the Canal Zone, where populations consist entirely of intergrades between corvina and hicksii, and where no pure parental types occur. The name "aurita" the application of which is dubious in any case, is tentatively used for these intergrades. 382 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON Sporophila americana corvina (Sclater) Spermophila corvina Sclater, 1859, Proc. Zool. Soc. London 1859:379. Playa Vicente, Oaxaca, Mexico. Spermophila badiiventris Lawrence, 1865, Ann. Lye. Nat. Hist. N.Y. 8:172. Greytown, Nicaragua. Type re-examined for this study. Characters.—Adult males almost entirely black, with only the speculum of the wing and midline of belly white. Speculum smaller than in hicksii. Females and subadult males are markedly darker and more sooty than in other subspecies, but have not been considered in determining the distribution or extent of intergradation in any of the forms. Range.—Caribbean slope of southeastern Mexico, south through Bocas del Toro, Panama. The few specimens known from the Caribbean slope between Bocas del Toro and the Canal Zone are nearly pure corvina, but show faint traces of white on the sides of the neck. I have designated these as "0+" in the hybrid index discussed in the account of S. a. "aurita," but have listed these specimens below under corvina. Specimens examined (only specimens from Costa Rica and Panama are listed although others were examined).—COSTA RICA. GUANACASTE; ca. 3 miles E Tilaran, 950 m (1, LSU); Arena!, 500 m (1, LSU). ALAJUELA: Naranjo (1, USNM); Villa Quesada (1, USNM). HEREDIA: Puerto Viejo (1, LSU). CARTAGO: Bonilla (6, USNM; 4, AMNH); Guayabo (3, USNM); Tucurrique (1, AMNH); Aquiares (1, AMNH). SAN JOSE: Carillo (3, AMNH; 1, USNM). LIMON: Cariari (4, WFVZ); Finca La Lola, Rio Madre de Dios (1, WFVZ); Jimenez (2, USNM); San Bernardo (1, USNM); Sipurio (2, USNM); Uva(l, USNM); Limon (3, AMNH); Guapiles (2, AMNH); Siquirres (1, AMNH); Atalanta (2, AMNH). PANAMA. BOCAS DEL TORO: Almirante (5, USNM; 4, AMNH); Changuinola (1, USNM); Cocoplum (7, ANMH); "Bocas del Toro" (I, ANSP). The following were ranked "0+," or almost pure corvina, in the hybrid index discussed below: VERAGUAS: Rio Calovevora, Caribbean slope (1, AMNH); COCLE: Tigre, head of Rio Guabal (I, USNM); El Uracillo, Rio Negro (1, USNM). COLON: Chilar, Rio Indio (1, USNM). CANAL ZONE: Gatun (1, USNM); Gamboa Pipeline Road (1, USNM). Sporophila americana hicksii (Lawrence) Spermophila hicksii Lawrence, 1865, Ann. Lye. Nat. Hist. N.Y. 8:171. "Panama" (probably = Buenaventura, Colombia, see below). Type reexamined for this study. Spermophila aurita chocoana Meyer de Schauensee, 1950, Proc. Acad. Nat. Sci. Phila. 52:138, Nuqui, Choco, Colombia. VOLUME 94, NUMBER 2 383 Characters.—Adult males with throat, sides of neck, lower breast and abdomen, rump, undertail coverts, and speculum white; pectoral band and variable amount of chin black. Range.—Pacific coast of Panama from central Veraguas and the Azuero Peninsula east (skipping the Canal Zone) through Panama Province and Darien, the Atlantic slope in San Bias, south along the Pacific slope of Colombia to the vicinity of the Rio Dagua, Valle. Specimens examined.— PANAMA. VERAGUAS: Sona (5, USNM); La Colorada, Santiago (2, AMNH); E shore of Montijo Bay, 1 mile S of Angulo River mouth (2, CM); Isla Gobernadora (2, USNM; one of these is more similar to those from Isla Coiba). LOS SANTOS: Tonosi (1, USNM). COCLE: Gago (1, USNM). PANAMA PROVINCE: Pacora (1, USNM); Chiman, Rio Chiman (1, USNM); Charco del Toro, Rio Maje (2, USNM). SAN BLAS: Mandinga (2, USNM); Perme (2, MCZ); Puerto Obaldia (3, USNM, 1 MCZ). DARIEN: Cana (4, USNM; 3, MCZ); mouth of Rio Paya, Rio Tuira (1, USNM); Pucro, Rio Pucro (1, USNM); Jaque (5, USNM); El Real, Rio Tuira (5, AMNH); Boca de Cupe, Rio Tuira (3, AMNH); Rio Sambu (1, ANSP). COLOMBIA. CHOCO: Nuqui, Rio Jurubida (4, ANSP); Nuqui (2, USNM); Acandi (5, USNM); Jurado (1, AMNH; 1, ANSP); Rio Baudonde (1, ANSP); Quibdo (1, ANSP); upper Rio Baudo (1, ANSP); Andagoya (1, ANSP). ANTIOQUIA: Dabeiba, Rio Sucio (1, AMNH); Villa Arteaga (2, USNM). CORDOBA: Socarre, Rio Sinii (1, USNM). CALDAS: Santa Cecilia (3, ANSP). VALLE: Punta Muchimbo, Rio San Juan, 1 mile S of mouth of Rio Calima (2, USNM); San Jose (1, USNM); Buenaventura (2, USNM). Remarks.—When Meyer de Schauensee (1950) described chocoana, he compared it with birds from Costa Rica, western Panama, and the Canal Zone, all of which were considered to represent aurita and all of which have black throats. He recognized that birds from Colombia and Darien differed in consistently possessing a white throat and he therefore segregated these under the name chocoana. A major problem arises here in the nature and orgin of the type specimen of hicksii Lawrence (USNM 40300). Meyer de Schauensee (1950:139) reported that "Mr. Herbert Deignan has kindly examined the type of hicksii for me and writes me that although it is a white-throated example, it was collected by Hicks 'probably not far from the city of Panama.' It therefore must be regarded as an aberrant example of 5. a. aurita.'''' The type of hicksii, which I have examined, is a perfectly typical example of chocoana, with a pure white throat and rump. It shows not a trace of the intergradation with corvina that marks "aurita." The specimen is labelled simply "Panama," the implication being that it came from the vicinity 384 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON of Panama City, on the Pacific slope. No such individuals with pure white throats from the vicinity of Panama City or the Canal Zone exist in any of the collections I have examined, although they have been taken on the Pacific slope both to the east and to the west of the Canal Zone area. The type of hicksii was sent to S. F. Baird at the Smithsonian Institution by Fred Hicks in a lot of 54 specimens, all of which came from Panama except for 4 from Call, Colombia, and 12 from Buenaventura, Colombia (letter of 27 December 1864 from Hicks to Baird; accession file 588, USNM). Not all of these specimens were catalogued. The type of hicksii was catalogued immediately following 3 specimens of the same species labelled as being fr

Abstract: First record of the Variable Seedeater (Sporophila americana) for the state of Maranhao, Brazil

Abstract: Birds of the open, humid lowland tropics encounter challenging thermal con- ditions-high temperatures, high humidity, and intense solar radiation. I examined how one such species, the Variable Seedeater (Sporophila aurita, Emberizidae), responds to tempera- ture by measuring its body temperature (Tb), metabolic heat production (Hm calculated from oxygen consumption), and evaporative heat loss (HIf calculated from evaporative water loss) at stable air temperatures (Ta) between 14 and 460C. I also measured basal metabolic rate (BMR) and Tb of the Variable Seedeater's diminutive (7.5 g) congener, the Ruddy-breasted Seedeater (S. minuta). All measurements utilized fasted, active-phase birds that were resting in the dark. BMR was lower than expected allometrically in both species, averaging 76% of predicted (or 0.718 kJ/h) in the 9.8-g Variable Seedeater (n = 11) and 67% of predicted (or 0.525 kJ/h) in the Ruddy-breasted Seedeater (n = 3). The Variable Seedeater's thermoneutral zone (TNZ) was relatively high (28.9 to 39.2'C). Below the TNZ, Hm was linearly related to Ta as follows: Hm (kJ/h) = 2.22 - 0.052 Ta. Thermal conductance, as indicated by the slope of this relation, was 12% lower than predicted allometrically. Data for 14 tropical bird species show BMR and thermal conductance to be linked; species with relatively high thermal con- ductance have a high BMR and vice versa. Evaporative cooling is relatively ineffective in the humid tropics, and compared with most birds Variable Seedeaters have a blunted evapo- rative response to heat. They dissipate evaporatively a maximum of 127% of their metabolic heat production at high Ta, even when measured in air only half as humid as that of their native habitat. Consequently, Variable Seedeaters employ hyperthermia (elevated Tb ) to cope with heat. They are more tolerant of hyperthermia than most bird species and survive Tbs that are among the highest recorded for birds (46.8 to 47.0?C). Tolerance of hyperthermia is advantageous because it allows Variable Seedeaters to maintain an unusually large Tb-T, gradient in hot environments (0.8 to 1.4'C at Ta = 43?C), and thereby to dissipate heat pas- sively. Variable Seedeaters are able to circumvent partially the well-known temperature de- pendency of chemical reactions (i.e. the Arrhenius-van't Hoff effect). This enables them to become progressively hyperthermic at Tas above 35'C with relatively little increase in met- abolic heat production, their Hm increasing at only 52% of the allometrically predicted rate above the TNZ. Variable Seedeaters possess several traits that enhance their tolerance of high Ta, yet because of their small size and limited thermal inertia their principal response to heat stress in the field is to avoid it behaviorally rather than to overcome it physiologically.