Ecology, Behavior and Social Organization of Saffron-Cowled Blackbirds (Xanthopsar Flavus)

ORNITOLOGIA NEOTROPICAL 16: 15–29, 2005 © The Neotropical Ornithological Society

ECOLOGY, BEHAVIOR AND SOCIAL ORGANIZATION OF SAFFRON-COWLED BLACKBIRDS (XANTHOPSAR FLAVUS)

Rosendo M. Fraga

Tucumán 335, Piso 11C, 1049 Buenos Aires, Argentina. E-mail: [email protected]

Resumen. – Ecología, comportamiento y organización social del Tordo Amarillo (Xanthopsar flavus). – La ecología de la conducta y la organización social del Tordo amarillo (Xanthopsar flavus) se inves- tigó entre 1995 y 2004, principalmente en Argentina y Paraguay; también se obtuvo información de una pequeña población cautiva. Según una reciente filogenia molecular, este ictérido y ambas especies del genero Pseudoleistes forman un clado monofilético bien definido (clado Pseudoleistes). El Tordo Amarillo muestra un mínimo dimorfismo sexual en tamaño, pero un marcado dimorfismo sexual en coloración, concordando y discordando, respectivamente, con los Pseudoleistes. El Tordo Amarillo se alimenta principalmente de artrópodos obtenidos por “gapeo” en el suelo o en vegetación baja. Nidifica como parejas monógamas en la vegetación acuática emergente de humedales, o en la vegetación herbácea en sitios secos. La nidificación puede ser solitaria o en pequeñas colonias de hasta 40 parejas. Los machos alimentan a los pichones tanto como las hembras, y se observaron machos ayudantes (helpers) en dos de seis nidos o gru- pos aislados con volantones. El repertorio vocal del Tordo Amarillo es relativamente exiguo (menos de 10 vocalizaciones) y mayormente compartido por ambos sexos. En todos estos aspectos, el Tordo Amarillo se asemeja a los Pseudoleistes, aunque su organización parece menos compleja. Una hipótesis basada en la dis- tribución filogenética del uso de humedales y conducta parental en ictéridos predijo que tanto la poliginia como un cuidado paterno mínimo se deberían dar en el clado Pseudoleistes, pero la predicción se basa en una categorización floja del hábitat y conducta territorial de estas especies. Abstract. – The behavioral ecology and social organization of Saffron-cowled Blackbirds (Xanthopsar flavus) was investigated between 1995 and 2004, mostly in Argentina and Paraguay. In addition, some data were obtained from a small captive population. According to a new molecular phylogeny, this blackbird, plus the two Pseudoleistes marshbirds, forms a well-defined monophyletic clade (marshbird clade). Sexes of Saffron-cowled Blackbirds show minimal size dimorphism and marked color dimorphism, agreeing and disagreeing with the marshbirds. The blackbird feeds mostly on arthropods by gaping in the ground or in low vegetation, and breed as monogamous pairs either in marsh emergent vegetation, or in herbaceous vegetation in dry soil. Nesting occurs solitarily, or in small colonies of up to 40 pairs. Males feed chicks at similar rates than females. Male helpers were observed in two of six isolated nests or postfledging groups. The vocal repertory of Saffron-cowled Blackbirds is comparatively small (less than 10 vocalizations) and mostly shared between the sexes. Saffron-cowled Blackbirds closely resemble the marshbirds in all those aspects, but their social organization seems less complex. An hypothesis based on the phylogenetic distribution of marsh nesting and parental behavior in icterids predicted that polygynous mating and minimal male care should occur in the marshbird clade, but the prediction was based on weak categorizations of habitats and territorial behavior. Accepted 22 November 2004. Key words: Saffron-cowled Blackbird, Xanthopsar flavus, displays, vocalizations, breeding organization, behavioral evolution, molecular phylogeny.

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INTRODUCTION icterids. In the new phylogenetic tree (Lanyon & Omland 1999, Johnson & Lanyon 1999), The Saffron-cowled Blackbird (Xanthopsar fla- Saffron-cowled Blackbirds are ancestral to an vus), a red data book species, survives in frag- exclusively South American clade containing ments of its former distribution in Argentina, also the marshbirds of the genus Pseudoleistes Brazil, Paraguay and Uruguay (BirdLife Inter- [Brown-and-yellow (P. virescens), Yellow- national 2002). Recent literature on the spe- rumped (P. guirahuro)]. The clade containing cies is mostly concerned with conservation Saffron-cowled Blackbirds and the marsh- issues (Fraga et al. 1998, Azpiroz 2000, Dias & birds (marshbird clade) was classified as Maurício 2002). Natural history and behav- marsh-nesting and, by being monogamous, it ioral data is included in some of those papers, was a clear exception to the trend. On the as well as in Belton (1985) and in the older lit- other hand, the nearest icterids outside this erature (e.g., Gibson 1885, Hudson 1920). clade, the Yellow-hooded (Chrysomus ictero- However, a detailed account of the behavioral cephalus )and Chestnut-capped Blackbirds (C. ecology (including vocalizations) of this ict- ruficapillus), agreed with the hypothesis, as erid has not been published. This paper pre- both species (formerly included in Agelaius) sents new behavioral data on Saffron-cowled are marsh-nesting, polygynous and have Blackbirds, obtained in Argentina, Uruguay unequal parental care (Lowther et al. 2004). and Paraguay, and summarizes our knowledge The poverty of information on South Ameri- on the social organization of the species. can icterids, even on basic subjects like habi- The behavioral ecology of some icterid tat, food and general ecology, made more species has been intensively studied, with difficult the analysis of Searcy et al. (1999). important reviews that summarize data and The subject is discussed here using more propose ideas on the evolution of social updated comparative data. behavior and organization within the family (e.g., Orians 1985a, 1985b; Robinson 1986). MATERIALS AND METHODS The information on behavior and ecology of Saffron-cowled Blackbirds is discussed in this Saffron-cowled Blackbirds were observed at context. Thanks to a new molecular phylog- 36 localities in Argentina (provinces of Corri- eny of the family (Lanyon & Omland 1999, entes and Entre Ríos), Uruguay (departa- Johnson & Lanyon 1999), more rigorous mento Rocha) and Paraguay (departamentos approaches to behavioral evolution in the Ict- Misiones, Caazapá and Itapúa). Coordinates eridae are now possible (Searcy et al 1999). of localities where the species was observed Scientific names in this paper follow the last were obtained with a GPS receiver, and dis- version of the South American Checklist tances between localities and occupied areas Committee of the American Ornithologists’ were estimated with Arc View GIS. The area Union (Remsen et al. 2004). Lowther et al. most frequently visited was located around (2004) cover the nomenclatural history of the Perdices (33º16´S, 58º34´W) in southeastern genus Agelaius (formerly including Xanthopsar) Entre Ríos. A total of 127 days and approxi- and state the reasons for the recent generic mately 500 h of field observations (from changes. October 1995 to March 2004) are included in The phylogenetic analysis of Searcy et al. this report. A total of 17 nestlings and fledg- (1999) suggested that a switch to marsh-nestlings were color banded for individual identi- ing was crucial for the evolution of polygy- fication. nous mating and unequal parental care in the Data were also obtained from a group of

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TABLE 1. Body masses (g), sexual size dimorphism and color dimorphism in Saffron-cowled Blackbirds and their four closely related species, according to molecular phylogeny. Sample sizes are given for males and females. Size dimorphism is expressed as the ratio of mean male body mass/mean female body mass.

Species Mass N Sexual dimorphism Male Female Male Female Size Color Chestnut-capped Blackbird (Chrysomus ruficapillus) 41.5 32.0 5 3 1.297 Yes Yellow-headed Blackbird (C. icterocephalus) 34.5 26.7 11 14 1.292 Yes Safron-cowled Blackbird (Xanthopsar flavus) 41.1 38.3 11 10 1.073 Yes Yellow-rumped Marshbird (Pseudoleites guirahuro) 91.2 81.9 6 3 1.113 No Brown-and-yellow Marshbird (P. virescens) 79.6 72.9 62 56 1.092 No

Sources: Personal unpubl. data; publications: Belton (1985), Darrieu & Camperi (1998), Magalhaes (1999), Fraga & Di Giacomo (2004); label data on specimens at the American Museum of Natural History, New York, the Field Museum of Natural History, Chicago, and, for Yellow-headed Blackbirds, the Colección Ornitológica Phelps, Caracas. nine captive blackbirds (seven males and two from the literature (Belton 1985, Darrieu & females, all color banded for individual recog- Camperi 1998, Magalhaes 1999, Fraga & Di nition) donated by bird catchers in Buenos Giacomo 2004) and label data on specimens Aires, and captured at unprecise localities of at the American Museum of Natural History Corrientes and Entre Ríos provinces. This (New York), Field Museum of Natural His- captive population was kept in a 64 m2 out- tory (Chicago), and the Colección Orni- door aviary near Luján, Buenos Aires Prov- tológica Phelps ( Caracas). ince, Argentina, from 15 May to 23 October I recorded bird vocalizations with an 1998, with a special permission from the pro- AKG C568 EB shotgun microphone and a vincial government. The rehabilitated black- Sony Walkman Professional cassette recorder. birds were afterwards released in a private All vocalizations used in this paper were nature reserve in Buenos Aires Province spontaneous, i.e., no playback was used. One (BirdLife International 2000), and monitored vocalization of each recognizable type, and for some weeks. with a minimum background noise, was Sexes of adult Saffron-cowled Blackbirds selected for each individual; if more than one are easily recognizable by differences in color- good sonogram were available for one indi- ation (Ridgely & Tudor 1984). Chicks out of vidual, I used the mean measurements. For the nest and dependent juveniles resemble each vocalization I measured the following females and cannot be sexed in the field, but variables: total duration (s) and emphasized differ from adults of both sexes in having yel- (or peak) frequency (kHz); these two variables lowish gray rumps (versus bright yellow) and are little affected by sound volume or record- pinkish-red palates (versus black) (Fraga et al. ing quality. Temporal and acoustic variables 1998). were measured with the Cool Edit 2000 and My body mass data for Saffron-cowled Syrinx 2001 softwares, and sonograms printed Blackbirds (including some adults of the avi- with the last software (obtained from the Cor- ary population) were obtained with Pesola nell Laboratory of Ornithology, Ithaca, NY, scales. Body mass values for Saffron-cowled USA). Blackbirds and other icterids were obtained Comparative data on behavior, vocaliza-

17 FRAGA tions and nesting of the marshbirds and the open grasslands (campos) and the interior Chrysomus blackbirds are often taken from my Atlantic forest (López de Kochalka 1996, unpublished field observations and tape Madroño et al. 1998, pers. observ.). The “cam- recordings, obtained in NE Argentina (Bue- pos” are apparently an edaphic formation in nos Aires, Entre Ríos, Chaco, Corrientes), this region (Cabrera 1970). Paraguayan popu- Paraguay (Bajo Chaco, Ñeembucú, Misiones, lations of Xanthopsar may live and breed Itapúa), Brazil (Minas Gerais, Amazonas) and in large (50–100 ha) natural patches of grass- Venezuela (Sucre). Names of icterid displays land and marsh surrounded by dense sub- follow Orians & Christman (1968). Defini- tropical forest, or stands of the tree-sized tions of terms describing social organization, bamboo Bambusa angustifolia. This habitat is like “monogamy” and “territory” follow shared by Yellow-rumped Marshbirds. The Searcy et al. (1999). Helpers are individuals Saffron-cowled Blackbird population in the other than a mated pair that participate in the upper Tebicuary may well exceed 1000 indi- feeding and care of the chicks. viduals. The Perdices population in Entre Ríos, RESULTS estimated to 120 individuals, occupies rolling countryside with fertile agricultural and pas- Body mass and sexual dimorphism. Data on body ture soils, limited to the south by the flood- mass, sexual dimorphism in mass, and plum- plain of the Río Paraná delta. By plotting all age dimorphism of Saffron-cowled Black- my records, the area occupied by the Perdices birds and its four related species are in Table population is estimated to 282 km2. Saffron- 1. Clearly, Saffron-cowled Blackbirds resem- cowled Blackbirds are seldom seen in the ble the Chrysomus blackbirds in having sexual floodplain of the delta , but a small popula- dimorphism in plumage, but are similar to the tion of about 80 individuals was recently marshbirds in their slight size dimorphism. found at Ibicuy (33º44’S, 59º06´W), within Five males in the captive population had the delta; this population lives in a small ele- scattered brownish feathers (instead of vated area covered by old sand dunes, rem- orange yellow) in the front, and likewise nants of a mid-Holocene coastline (Iriondo brownish feathers in the otherwise black nape 1991). and back, suggesting a gradual acquisition of the adult plumage. By the presumed dates of Diet . The diet of Xanthopsar has been exam- capture indicated by the bird dealers, those ined mostly in Paraguay (López de Kochalka males were probably yearlings. 1996), using faecal analysis; it is mostly com- posed of insects and spiders (95% of the Habitat. In Argentina, Saffron-cowled Black- items), with a small percentage of seeds. My birds have been found in grasslands and own observations agree with those data; I marshes in open environments (Fraga et al. observed only three cases of seed consump- 1998). In the southern Pampas of Buenos tion, two involving cultivated plants. Sorghum Aires (37º15´S), the species formerly occu- seeds were taken from the plants, and small pied treeless areas (Doering & Lorentz 1879), groups of individuals sometimes consumed sharing the habitat with Brown-and yellow rice seeds left on rural roads by harvesting Marshbirds. At the northern end of its range machines. The aviary population rejected in Paraguay (upper bassin of the Río Tebi- seeds (even rice), but readily accepted insects cuary, 26º30´S), Saffron-cowled Blackbirds (larvae of Tenebrio). Insects consumed (López are found in the abrupt interface between de Kochalka 1996) include Hemiptera,

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Coleoptera, Diptera, Lepidoptera (caterpil- In Argentina, this association occurs mostly in lars) and Hymenoptera (ants). Corrientes, because Black-and-white Monji- Flying ants were captured when available, tas are rare and local in Entre Ríos (Fraga by mean of short sallies, and were offered to 2003). The monjita is a hypothetical species in chicks. Otherwise, most prey were obtained Paraguay (Hayes 1995) so this association on the ground, the top soil, or in low vegeta- does not occur everywhere within the range tion, with much use of gaping. Gaping was of Saffron-cowled Blackbirds. not only used in the soil, but also to search in Besides the Black-and-white Monjita, I the basal leaves of Eryngium and other plants. saw foraging flocks of blackbirds following In the aviary, some individuals squatted on the the movements of other birds (icterids and ground while probing and gaping. Foraging tyrant flycatchers) and landing near them. The flocks were rather compact (small inter-indi- icterids more frequently followed were the vidual distances) and, when moving, often two marshbirds (Fraga et al 1997). The aviary exhibited “rolling” behavior, with the rear population joined a flock of Brown-and-yel- individuals flying on top of the first ones. low Marshbirds within 15 min of being released in the wild. Flycatchers followed by Flocks and flocking behavior. With four excep- Saffron-cowled Blackbirds included the tions, I found Saffron-cowled Blackbirds in Streamer-tailed Tyrant (Gubernetes yetapa) in groups or flocks of 2 to 240 individuals. Flock Paraguay and Corrientes, and rarely the Scis- sizes of Saffron-cowled Blackbirds varied sor-tailed Flycatcher (Tyrannus savanna) in considerably between seasons and localities Entre Ríos. On the other hand, Gray Monjitas (Fraga et al. 1998, Dias & Maurício 2002). (Xolmis cinerea) attacked and expelled two Flocks of up to 470 individuals have been groups of blackbirds that landed below their reported from Paraguay (BirdLife Interna- perch. tional 2000). The largest flock I observed in Concerted attacks on birds (other than Argentina (approximately 240 individuals) was predators and parasites) by groups of Saffron- found around a winter roost in Corrientes. cowled Blackbirds have been reported Sentinel behavior has been reported for (Madroño et al. 1998). In Entre Ríos, I once the species (Hudson 1920, López de Koch- saw attacks on Eared Doves Zenaida auriculata alka 1996) and I observed some cases. How- that foraged on the ground. Male Saffron- ever, more frequently Saffron-cowled cowled Blackbirds sometimes attack other Blackbirds depended on the sentinel behavior birds when setting a nesting colony (Belton of associated bird species (López de Kochalka 1985). 1996, Fraga et al 1998, and below). In presence of avian predators like Sharp-shinned Agonistic behavior. Saffron-cowled Blackbirds Hawks (Accipiter striatus) or Aplomado Falcons threat conspecifics with a “bill up” display, (Falco femoralis), flying flocks in Perdices raising the head and bill, and often walking or moved in a compact, spheroid-shaped forma- flying in this position towards other individ- tion. ual. I saw both sexes using this display. Most agonistic behavior is seen in breeding colonies Interactions with other birds. Most authors (Bel- (Belton 1985). Fighting and chasing in the avi- ton 1985, Fontana & Voss 1995, Azpiroz ary population occurred during the first three 2000) have stressed the remarkable associa- months (May–July), and was afterwards tion of Saffron-cowled Blackbirds with the replaced by threat displays and avoidance. As Black-and-white Monjita (Xolmis dominicana). expected, males with brownish feathers

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(subadults) were displaced from perches Colonial nesting is also the rule in Paraguay or foraging positions by adults. No special (Madroño et al. 1998, pers. observ.) and Brazil appeasement displays (e.g., allopreening) from (Belton 1985, Dias & Mauricio 2002). Solitary the subordinate individuals were seen. or colonial nesting occurs in Entre Ríos province, where I found four solitary nests in the Sexual behavior. Aerial courtship flights (sexual incubation or nestling stages, built on low chases), similar to those of other icterids (Ori- shrubby vegetation along rural roads. Besides, ans & Christman 1968), were seen in Para- at least six isolated pairs were seen during the guay and Argentina. Perched courting males early breeding season, apparently looking for showed a display partially resembling the similar nest sites along roadsides in this prov- “song spread” of other icterids (Orians & ince. Solitary nesting seems more frequent in Christman 1968): the wings were lowered and Uruguay, reflecting perhaps population curved, exposing the yellow rump, and the tail declines (Azpiroz 2000). Nevertheless, two feathers were spread like a fan. However, dif- blackbird colonies of 10 and 12 pairs were fering from similar displays in Nearctic Age- reported from that country (Gibson 1885, A. laius, the head of Saffron-cowled Blackbirds Azpiroz pers. comm.) pointed upwards, and the body feathers were Preliminary data on colony locations for not fluffed. Song is usually delivered in this Argentina can be found in Fraga et al. (1998). posture, which sometimes preceded copula- Updating that information, all the 11 nesting tion. One male in Entre Ríos displayed on the colonies I observed in Perdices were in dry or ground to a female perched above it, clearly upland terrain; nests were built in either showing its bright yellow rump surrounded native herbaceous plants or introduced weeds by black plumage. (once also on the ground). Elsewhere in Pairing behavior between two dominant Entre Ríos, historical sources mention a col- males and the two females took place in the ony in a marsh (Barrows 1883) and another in captive population towards July. When the thistles and low shrubs along a roadside hedg- birds were released, the paired males flew to erow (Klimaitis 1984, I visited the site in their respective females and performed stan- 1996). Before extinction, the population dard courtship behavior. Data from Corri- around Buenos Aires city also nested on dry entes and Entre Ríos also indicate that pair ground (Hudson 1920, Pereyra 1933). One formation occurs before the females select historical record for western Uruguay indi- nesting sites, as in the Yellow-rumped Marsh- cates a colony in dry terrain (Gibson 1888), birds (Fraga & Di Giacomo 2004). and local people interviewed in 2003 in The main sexual display of females was this area mentioned this fact. Elsewhere silent: the female crouched on the ground or in Corrientes, Argentina (Fraga et al. 1998), on a perch, raised the tail and quivered the Brazil (Belton 1985, Dias & Mauricio 2002), wings. This display was not always followed eastern Uruguay (Azpiroz 2000) and Para- by copulation, and was observed months guay (Madroño et al. 1998, pers. observ.) Saf- before the breeding season (e.g., late August). fron-cowled Blackbirds nest in emergent veg- As noted by Belton (1985), the display was etation in marshes and bogs, including seen also in agonistic contexts, particularly in abandoned ricefields. Arboreal nesting has conflicts between neighbor nesting pairs. not been reported for Saffron-cowled Black- birds. Nesting behavior. Most nests were built in small In Perdices, most colonies were located colonies of 3 to 40 pairs (Fraga et al 1998). within or near nesting groups of White-

20 SAFFRON-COWLED BLACKBIRD browed Blackbirds (Sturnella superciliaris), 10 days. Colonies were occupied for 30 to 45 which have a similar breeding season. This ict- days. erid could also be considered a colonial nester, although its nests were more scattered Parental behavior. Breeding Saffron-cowled than those of Saffron-cowled Blackbirds Blackbirds appear to form monogamous (pers. observ.). Both species tolerated each pairs. Only the females build the nest, incu- other, and even attacked together avian bate eggs and brood chicks. Males perform predators like Long-winged Harriers (Circus most nest guarding and most attacks on avian buffoni), and Shiny Cowbirds (Molothrus bona- nest predators and parasitic Shiny Cowbirds riensis). In Paraguay nesting colonies were (Molothrus bonariensis); however, females were often close to nests of Yellow-rumped Marsh- also observed attacking nest predators like birds, which are aggressive to raptors (Fraga Chimango Caracaras (Milvago chimango). A & Di Giacomo 2004). Persistent (or tradi- male was seen feeding its incubating mate in tional) use of specific nesting areas or sites Entre Ríos; as few nests were intensively by Saffron-cowled Blackbirds was not watched during this stage, this behavior may observed in Entre Ríos, where agricultural be more widespread. Males were observed practices constantly changed the landscape. performing other parental behavior, like guid- However, an abandoned rice field in Corri- ing a recently fledged brood away from the entes was used for a minimum of four breed- nest (and myself), by repeatedly landing with ing seasons. Similar data exists for some sites quivering wings near the chicks. in Paraguay. During non-systematic observations at six Nest clumping in Saffron-cowled Black- broods or nests (Argentina and Paraguay) birds reached a density of almost 56 nests/ha chicks in and out of the nest were fed by both in one colony (Fraga et al 1998). Inter-nest dis- sexes at roughly equal proportions (29 feeding tances ranged from 3 to 18 m. Saffron-cowled trips for males, 33 for females). By contrast Blackbirds have been classified as territorial with most South American icterids (Orians breeders (Searcy et al 1999). However, nesting 1980), provisioning adults frequently carried pairs in colonies defended (at most) small several prey items per feeding trip. All identi- areas around the nest, and did not defend fied items were insects, including Orthoptera feeding territories. In all the Perdices colonies, (Tettigoniidae, Acrididade, mostly green-col- nesting birds foraged and gathered most of ored), Mantidae, Hymenoptera (reproductive the food for chicks outside the colony, often alates of ants) and larvae of Lepidoptera flying hundreds of meters to do so. Solitary (mostly green-colored). Emergent aquatic pairs feeding nestlings also collected food at insects, prominent in the diet of other marsh- similar distances. nesting blackbirds (Orians 1980), were not observed. Similar observations (equal sexual Breeding season and nesting synchrony. Based on roles and food items) have been reported egg-laying dates, Saffron-cowled Blackbirds from Uruguay (Azpiroz 2000). nested from October to December. Data on Azpiroz (2000) first reported helpers at clutch sizes, incubation and nestling periods the nest in Uruguayan Saffron-cowled Black- can be found in Fraga et al. (1998). The breed- birds. His sample comprised 10 isolated nests, ing season is brief and no second broods were but no information on the frequency and sex detected. Data from Perdices also indicate of the helpers was given. Colonial nesting (the nesting synchrony within colonies, with 80% rule in Argentina and Paraguay) make more of the clutches laid within an interval of about difficult the observations of helping; without

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FIG. 1. Calls (“chucks”) from departing individuals of both sexes, 12 km NE from Santo Tomé, Corrientes province, Argentina (26 June 1999). banded individuals it was difficult to deter- males and one female. Both males were seen mine how many individuals were carrying carrying insects in their bills. On 28 Decem- food, and to which nests or chicks. The same ber 2000, I observed another isolated group comment applies to postfledgling groups pro- of four adult Saffron-cowled Blackbirds duced by colonies with multiple successful (three males, one female) and three fledglings; nests. all the adults caught flying ants that were My best data are therefore based on 6 iso- delivered to the begging juveniles. At least lated nests or postfledging groups (five from one male lacked full adult plumage. The only Entre Ríos, one from Corrientes); these isolated postfledgling group from Corrientes breeding units were located at distances of (30 November 1995) consisted of a pair more than 5 km from the nearest conspecif- attending one chick still barely able to fly. The ics. Two solitary nests in Entre Ríos which loud alarm calls of the adults attracted other survived to the late incubation stage were conspecifics (two males and one female), attended by unassisted pairs of blackbirds. but these were chased and threatened by The postfledging groups contained one the male parent. However, this pair tolerated female and no more than three chicks of sim- two Brown-and-Yellow Marshbirds near its ilar age; they could have originated from chick. undetected isolated nests, or from small colonies where a single nest survived (this last Vocal behavior. Individuals of both sexes in information was available in two cases). Two departing flocks usually exchange sonorous of three isolated postfledging groups in Entre “chuk” calls when flying away (Fig. 1). Other Ríos, observed for periods of 40 min or more, contact calls for both sexes sound like “cheg” had helpers. One group found on 3 Decem- or “kuk”. In sonograms the calls look like ber 2000 consisted of two recent fledglings stacks of chevron-shaped elements, lasting (color banded as nestlings), escorted by two 0.04 to 0.08 s, and with mean emphasized fre-

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FIG. 2. Alarm whistles of a male in a breeding colony, Perdices, Entre Ríos province, Argentina (7 Decem- ber 1997). quencies ranging from 2.01 to 4.36 kHz (n = duced two main calls, a soft contact “chew” 22 individuals, both sexes). There is some and the begging call, a longer, nasal “chwaaa” variation in frequency and structure of the (Fig. 3). One individual combined both in contact calls, possibly related to context. repeated series, and intermediate calls A loud ascending whistle (Fig. 2) was between both vocalizations commonly occur. commonly heard from males during the Both chick calls, particularly the “chwaaa”, breeding season, apparently alarmed because show considerable variation in length, fre- of my presence near a nest or a fledged chick. quency and harmonic structure, probably I also heard this whistle while a snake (Phi- related to context and motivation. The lodryas patagonica) was raiding a nesting colony “chwaa” calls may have up to 12 harmonics, in Entre Ríos (Fraga et al. 1998). I did with mean emphasized frequencies ranging not hear this call from females. Whistles from 2.29 to 5.46 kHz . (n = 7 males) lasted 0.25 to 0.44 s, with a The song is produced by both sexes (Belton range of emphasized frequencies covering 1985) but it is more frequent among males. I 2.94 to 4.43 kHz. When I approached recently obtained satisfactory song recordings from 26 fledged chicks, attending females produced males, but only from two females (Fig. 4). fast series of harsher calls “kuk”, perhaps a Most singing was produced by perched indi- variant of the contact call that functions like viduals, and singing in flight was heard mostly an alarm. during sexual chases. The songs comprise fast Individuals in the hand or trapped in mist introductory notes, followed by one to three nests produced series of rasping calls (no loud rasping notes, either ascending or recordings available), similar to “distress calls” descending. As defined by Marler (1969), of other icterids I have trapped [e.g., Baywings songs are frequency modulated, with a (Agelaioides badius)]. marked dissonant quality. The number of ele- The five fledged chicks I recorded pro- ments in a song range from one to six or

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FIG. 3. Calls of a fledged chick, Perdices, Entre Ríos province, Argentina. The short calls at 2.5 s are contact calls, the others are food-begging calls directed to the male (1 December 2001). seven; however, pauses between elements are response to the presence of another female not well defined in the sonograms, even dur- near the nest, or (rarely) a male other than the ing sudden changes in pitch. mate. Mated pairs produced song duets after Songs showed considerable variation in conflicts with neighbor pairs; the duets were duration and emphasized frequencies. Songs sometimes initiated by the female. of 28 individuals lasted from 0.29 to 1.13 s, with a mean (SD) of 0.85 (0.16) s. The DISCUSSION emphasized frequencies ranged from 2.94 to 7.16 kHz, with a mean (SD) of 4.33 (1.12) Saffron-cowled Blackbirds are similar to the kHz. Each marked male in the aviary popula- two Pseudoleistes marshbirds in their mainly tion had a distinctive song, clearly recogniz- insectivorous diet (Darrieu et al. 1996 for able in the sonograms. Likewise, songs of Brown-and-Yellow Marshbirds) and in forag- neighbor males in nesting colonies were dif- ing mostly on the ground. This similarity pos- ferent (Fig. 5). I could recognize in the field sibly explains their frequent interspecific the most distinctive song variants. association (Fraga et al. 1998). Contrasting Male songs occur throughout the year, with Saffron-cowled Blackbirds, both Chryso- and are produced even by individuals attend- mus blackbirds consume large amounts of ing fledged chicks. Group singing is frequent seeds, even in the breeding season, and are among males, as noted by Hudson (1920). In regarded as important pests of rice crops (e.g., the aviary population, song bursts involved ffrench 1976, Bello Falavena 1988, Bruggers up to five of the seven males, and were started & Zaccagnini 1994). The most unusual aspect by the two paired males. Female singing was of the foraging ecology of Saffron-cowled heard mostly during the nesting season, and Blackbirds is their frequent association with once in a flock with many fledged chicks. In tyrant flycatchers and the marshbirds, best nesting colonies, it apparently occurred in interpreted as an antipredator strategy (Fon-

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FIG. 4. Songs of two neighboring males in a breeding colony, Perdices, Entre Ríos province, Argentina (25 November 2000). tana & Voss 1995, Fraga et al 1998). Possibly gest that cooperative breeding is less frequent the blackbirds’ conspicuous coloration and among Saffron-cowled Blackbirds, with help- relatively small size make them particularly ers occurring mostly during the late nestling vulnerable to avian predators in open habitats. and postfledging stages. However, a more In their social organization, breeding Saf- extensive research with color banded adults fron-cowled Blackbirds closely resemble the could reveal a higher frequency of helping. two marshbirds (Orians et al. 1977, Fraga & Non-breeding groups of both marshbirds Di Giacomo 2004), in nesting solitarily or in show seemingly “altruistic” behaviors like the small colonies. By contrast, the two Chrysomus presence of flock sentinels, and the persistent blackbirds commonly nest in large colonies mobbing of avian predators (Mermoz & reaching up to 350 nests (Bruggers & Zaccag- Reboreda 1998, Fraga & Di Giacomo 2004), nini 1994); perhaps this degree of clumping is far more regularly than Saffron-cowled Black- related to their granivorous diet. Pairing in birds. Saffron-cowled Blackbirds appear to be Saffon-cowled Blackbirds appears to be in a more simple stage of social organization monogamous, as in the marshbirds (Orians et than the marshbirds. al. 1977, Fraga & Di Giacomo 2004.). Male Data presented here show that ecological Saffron-cowled Blackbirds provide a consid- and behavioral categorizations (marsh-nesting erable fraction of chicks´ food, as in the and territoriality) of the marshbird clade in marshbirds. This contrasts with the reduced the analysis of Searcy et al. (1999) should be provisioning role of Chrysomus males (Wiley & reconsidered. Belton (1985) stressed the fact Wiley 1980, Lyon 1997). that the narrow boggy swales used as nesting Helpers are regularly present in the nests habitat by Saffron-cowled Blackbirds in the of both marshbirds (Orians et al. 1977, Fraga southern Brazilian highlands are not typical & Di Giacomo 2004), from the incubation to marshes, having little standing water. The the postfledging stages. My limited data sug- nesting habitat of Saffron-cowled Blackbirds

25 FRAGA

FIG. 5. Male-female song duet in a breeding colony, Perdices, Entre Ríos province, Argentina (25 Novem- ber 2000). also includes grassland and even open of Saffron-cowled Blackbirds are widespread savanna on dry terrain, and the same com- in the family (Orians 1985b). The courtship ment applies to the marshbirds (Orians et al. display of male Saffron-cowled Blackbirds, 1977, Mermoz & Reboreda 1998, Fraga & Di less complex than the song spread display of Giacomo 2004). The three species rarely for- Nearctic Agelaius blackbirds (Orians & Christ- age in water or aquatic plants, and may breed man 1968), is similar to the perched courtship in emergent marsh vegetation to escape nest display of singing male Yellow-rumped predators, or the human-induced grassland Marshbirds, which also exhibit their bright fires so frequent in Paraguay and Corrientes. yellow rumps (Jaramillo & Burke 1999, pers. My data indicate that Saffron-cowled Black- observ.). birds are non-territorial, and that pair forma- Buzzing, nasal or rasping sounds similar tion takes place in the mobile non-breeding to those of Saffron-cowled Blackbirds occur flocks rather than in fixed male territories vis- in the songs of a large number of icterid spe- ited by females. The same pattern occurs in cies, Nearctic and Neotropical (Hardy et al. marshbirds (Orians et al. 1977, Mermoz & 1998, Orians 1985a), including the two Chry- Reboreda 1998, Fraga & Di Giacomo 2004). somus blackbirds and the Yellow-rumped Monogamy may prevail in the marshbird Marshbird (Hardy et al. 1998, my own record- clade by a combination of habitat and behav- ings). The songs of Saffron-cowled Black- ior. By contrast, males defend fixed territories birds are characterized by being shorter, and display to visiting females in the two simpler and with a peculiar tonal quality. Con- Chrysomus blackbirds (Wiley & Wiley 1980, tact and distress calls of Saffron-cowled Lyon 1997, pers. observ.), showing the pre- Blackbirds are similar to equivalent calls of dicted association between marsh habitat, ter- other icterids (Orians 1985a). Begging calls of ritorial behavior and polygynous mating. Saffron-cowled Blackbird chicks sound and The agonistic displays found in both sexes look (in sonograms) much like those of

26 SAFFRON-COWLED BLACKBIRD

Pseudoleistes marshbird chicks, particularly the the Ríos family from San Miguel Potrero. G. Yellow-rumped Marshbird. Ledec showed in many positive ways his inter- Even if I missed some types of vocaliza- est in the study and conservation of the spe- tions, the vocal repertory of Saffron-cowled cies. Data in 2003 were obtained thanks to a Blackbirds appears small (less than 10 vocal- project convened between the Convention on izations) and mostly shared by both sexes. Migratory Species (United Nations) and Aso- Xanthopsar blackbirds strikingly differ from ciación Guyrá Paraguay. For data on museum North American Agelaius blackbirds, where specimens, I thank the respective bird collec- male Red-winged (A. phoeniceus) and Tricol- tion curators. ored (A. tricolor) blackbirds have 18 and 17 different voices, respectively, versus six for REFERENCES females (Orians 1985a). This extensive male repertory is presumably correlated with their Azpiroz, A. B. 2000. Biología y conservación del non-monogamous mating system. Within the Dragón (Xanthopsar flavus, Icteridae) en la five Neotropical icterids discussed here, the Reserva de Biosfera Bañados del Este. Docu- most elaborate songs are produced by males mento de trabajo No. 29, Programa de Conser- of the polygynous Chestnut-capped Blackbird vación de Biodiversidad y Desarrollo (PROBIDES), Rocha, Uruguay. (Hardy et al. 1998, my own recordings). The Barrows, W. B. 1883. Birds of the lower Uruguay. songs, usually in contrasted sequences, last up Bull. Nuttall Ornithol. Club 8: 82–143. to 9 s, and include nasal buzzing sounds, Bello Falavena, M. A. 1988. Alguns dados sobre a musical trills, thin whistles, ascending scales, reproduçao do Garibaldi (Agelaius r. ruficapillus) sustained notes, and soft staccatto chords. As (Icteridae, Aves) em lavouras de arroz no Río in the polygynous oropendolas (Price & Grande do Sul. Rev. Bras. Zool. 4: 307–317. Lanyon 1992), this song complexity may have Belton, W. H. 1985. Birds of Rio Grande do Sul. evolved through sexual selection. Part 2. Bull. Am. Mus. Nat. Hist. 180: 1–241. The small repertory size of Saffron- BirdLife International. 2000. Threatened birds of cowled Blackbirds is comparable with the rep- the world. Lynx Edicions and BirdLife Interna- ertoires of 8–9 vocalizations reported for tional, Barcelona, Spain, and Cambridge, UK. Bruggers, R. L., & M. E. Zaccagnini. 1994. Verte- both sexes in the two marshbirds (Orians brate pest problems related to agricultural pro- 1985a, pers. observ.). Saffron-cowled Black- duction and applied research in Argentina. Vida birds are markedly dimorphic in plumage, but Silvestre Neotrop. 3: 71–83. almost monomorphic in vocal behavior. This Cabrera, A. 1970. La vegetación del Paraguay en el paradoxical situation should be the subject of cuadro fitogeográfico de América del Sur. Bol. further study. Soc. Argent. Bot. 11: 121–131. Darrieu, C. A., & A. R. Camperi. 1998. Fluctuación ACKNOWLEDGMENTS anual del peso corporal, tamaño de gónadas y muda de Pseudoleistes virescens (Pecho Amarillo E. Betbece, M. García Rams, A. Franzoy, M. Común) (Aves: Emberizidae, Icterinae). Neo- Codesido and J. Leiberman much facilitated tropica (La Plata) 44: 121–122. Darrieu, C. A., A. R. Camperi, & A. C. Cicchino. my field work in Argentina. G. Aprile, D. 1996. Ecología alimentaria de Pseudoleistes vire- Cicho and J. Pereyra provided excelent care scens (Vieillot 1819) (Aves, Icteridae), en ambi- and monitored the captive population. For entes ribereños del nordeste de la provincia de help in Paraguay, I am indebted to many peo- Buenos Aires, Argentina. Informe No. 51, ple, particularly A. Madroño, A. Yanosky, R. Comisión de Investigaciones Científicas Pro- Clay, S. Villanueva, M. Codesido, and also to vincia de Buenos Aires, La Plata, Argentina.

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Dias, R. A., & G. N. Maurício. 2002. Natural his- ceton, New Jersey. tory notes and conservation of a Saffron- Johnson, K. P., & S. M. Lanyon. 1999. Molecular cowled Blackbird Xanthopsar flavus population systematics of the grackles and allies, and the in the southern coastal plain of Río Grande do effect of additional sequence (CYT B and Sul, Brazil. Bird Conserv. Int. 12: 255–268. ND2). Auk 116: 759–768. Doering, A. , & P. G. Lorentz. 1879. La conquista Klimaitis, J. F. 1984. Hallazgo del Tordo de Cabeza del desierto. Diario de los miembros de la Amarilla en la provincia de Entre Ríos. Nues- Comisión Científica de la expedición de 1879. tras Aves 4: 7–8. Reprinted 1939. Comisión Nacional Monu- Lanyon, S. M., & K. E. Omland. 1999 A molecular mento al Teniente General. Julio A. Roca, Bue- phylogeny of the blackbirds (Icteridae): five lin- nos Aires, Argentina. eages revealed by cytochrome-B sequence data. Fontana, C. , & W. A. Voss. 1995 Padroes compor- Auk 116: 629–639. tamentais comuns de Heteroxolmis dominicana López de Kochalka, N. 1996. Evaluación del hábi- (Vieillot, 1823) (Tyrannidae) na savanna do tat, densidad relativa y situación del Chopí nordeste do Rio Grande do Sul, Brasil. Bio- Say´ju (Xanthopsar flavus) en San Miguel Potrero, ciencias (Porto Alegre) 3: 129–143. Departamento Itapúa, Paraguay. Informe final Fraga, R. M. 2003. Distribution, natural history and 8311, Entidad Binacional Yacyretá, Ayolas, Par- conservation of the Black-and-white Monjita aguay. (Heteroxolmis dominicana), a species vulnerable to Lowther, P. E., R. M. Fraga, T. S. Schulemberg, & extinction. Ornitol. Neotrop. 14: 145–156. S. M. Lanyon. 2004. Nomenclaturial solution Fraga, R. M., & A. Di Giacomo. 2004. Cooperative for a polyphyletic Agelaius. Bull. Br. Ornithol. breeding of the Yellow-rumped Marshbird Club 124: 171–177. (Icteridae) in Argentina and Paraguay. Condor Lyon, B. E. 1997. Spatial patterns of Shiny Cow- 106:671–673. bird brood parasitism on Chestnut-capped Fraga, R. M., G. Pugnali, & H. Casañas.1998. Natu- Blackbirds. Anim. Behav. 54: 927–939. ral history and conservation status of the Madroño, A., R. Báez, A. Esteche, C. Ojeda, A. endangered Saffron-cowled Blackbird Xanthop- Ríos & C. Ríos. 1998. Censo e historia natural sar flavus in Argentina. Bird Conserv. Int. 8: del Chopí Say´jú (Xanthopsar flavus) en San 255–267. Miguel Potrero y Estero Gómez, Itapúa. Asoci- Ffrench, R. 1976. A guide to the birds of Trinidad ación Guyrá Paraguay, Asunción, Paraguay. and Tobago. Harrowood Books, Valley Forge, Magalhaes, J. C. R. de. 1999. As aves da fazenda Pennsylvania. Barreiro Rico. Editora Pleiade, Sao Paulo, Bra- Gibson, E. 1885. Notes on the birds of Paisandú, sil. Republic of Uruguay. Ibis 1885: 275–283. Marler, P. 1969. Tonal quality of bird sounds. Pp. Hardy, J. W., G. B. Reynard, & T. Taylor. 1998. 5–18 in Hinde, R. A. (ed.). Bird vocalizations. Voices of the troupials, blackbirds and their Essays presented to W. H. Thorpe, Cambridge allies. Family Icteridae. Two cassette tapes with Univ. Press, Cambridge, UK. texts. ARA Records, Gainesville, Florida. Mermoz, M. E., & J. C. Reboreda. 1998. Nesting Hayes, F. E. 1995. Status, distribution and biogeog- success in Brown-and-Yellow Marshbirds: raphy of the birds of Paraguay. Monographs in efects of timing, nest site, and brood parasit- field ornithology No. 1, American Birding ism. Auk 115: 871–878. Association, Colorado Springs, Colorado. Orians, G. H., & G. M. Christman. 1968. A com- Hudson, W. H. 1920. Birds of La Plata. J. M. Dent, parative study of the behavior of Red-winged, London, UK. Tricolored and Yellow-headed blackbirds. Univ. Iriondo, M. H. 1991. El Holoceno en el litoral. Calif. Pub. Zool. 84: 1–81. Comun. Mus. Prov. Cienc. Nat. F. Ameghino 3: Orians, G. H., C. E. Orians, & K. J. Orians. 1977. 1–39. Helpers at the nest in some Argentine black- Jaramillo, A., & P. Burke. 1999. New World blackbirds. Pp. 137–151 in Stonehouse, B., & C. Per- birds. The icterids. Princeton Univ. Press, Prin- rins (eds.). Evolutionary ecology. Macmillan

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