Spectacled Tyrant Hymenops perspicillatus Scientific name definitions

For those from northern temperate regions, it seems ludicrous that a tyrant flycatcher could be so boldly and beautifully patterned as the Spectacled Tyrant. This is a looker of a bird, one that makes you do a double take. The bird is black, but also has a characteristic upright stance and long legs and chooses to perch in open and obvious places. On the face is a very large yellow spectacle created by a large fleshy orbital ring, similarly bright and noticeable is the yellowish white bill. This gives it the Argentine name of “pico de plata” or silver bill. But the black plumage comes to life when the bird takes flight and shows that what was hidden beneath all this black were largely white wings! The startling contrast of the white wings when the bird flies, is fantastic to see live. Not only that, the males perform a noticeable aerial display where they start perched on a noticeable perch and then fly up and circle vertically back to the perch, as they do so the white wings are in full display and a short wing snap occurs at the top of the circle which also creates a finger-snapping sound. This gives it the Chilean name “run-run” which is a child’s game that makes a whirring snapping sound. The female is very unlike the male, and often causes identification problems. She is largely brownish above with rusty wings and rusty streaking; below she is off white and streaked brown. In Chile and southern Argentina this species is highly migratory. As there are no wintering populations in western Peru or northern Chile it is clear that all Chilean Spectacled Tyrants cross the Andes to winter on the Argentine or Bolivian side of the mountains!

Male Spectacled Tyrant is easy to identify in the field and very distinctive across most of its geographic range by the combination of external features, which include black feathers, primaries mostly white (visible at rest), prominent greenish-tinged yellow fleshy wattle around eye, and bill pale yellow appearing almost white at distance. Within its range, male Spectacled Tyrant is superficially similar to White-winged Black-Tyrant (Knipolegus aterrimus), which is also shiny black overall, with large white band across inner webs of primaries (but usually hidden at rest). In addition, White-winged Black-Tyrant has a blue-gray tipped black bill and has no fleshy ring round eye.

The following description is based in part on Fjeldså and Krabbe (1990).

Distinctive, with prominent greenish-tinged yellow fleshy wattle around eye. Male is black overall; primaries mostly white with black base and tips (visible at rest, conspicuous in flight); iris yellow; bill pale yellow, appearing almost white at distance; legs black. Female is dark brown above, buffy or buff-white supercilium and pale lores, wattle reduced and duller; back streaked black with pale brown edges; two buffy wingbars, distinctive rufous remiges (visible in flight); tail dark; pale dusky or whitish below, dusky streaking across chest. Juvenile much like female.

Iris: yellow.

Bill: pale yellow, appearing almost white at distance.

Tarsi and toes: black.

Female bare parts as male, but bill dusky with brown lower mandible.

Total length: 13-16 cm; 14.5 cm (Fjeldså and Krabbe 1990)

Mass: Males. 2 males 23.5 g, 24.7 (Salvador 1990), 1 male: 21.2 g (Salvador and Di Giacomo 2014); 7 males mean: 20.2 g (range 16.8–21.4 g) (Navas and Bó 2001). Females. 3 females mean: 19.9 g (range: 19-20.7 g), 1 female: 21 g. (Salvador and Di Giacomo 2014); 1 female 20 g (Navas and Bó 2001).

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It was described for the first time by Gmelin (1789) as Motacilla perspicillata, with a type locality of Montevideo, Uruguay. The genus Hymenops was proposed by the French naturalist René Primevère Lesson in 1828, with perspicillatus as the type (and only) species. Name formerly used for genus was Lichenops (Sundevall 1836), but Hymenops has priority. Ohlson et al. (2013) proposed dividing Tyrannidae into 5 families. According to the approach proposed by this authors, Hymenops remain in Tyrannidae, in a Fluvicolinae subfamily (Swainson, 1832-1833), in a new Xolmiini tribe (Tello et al. 2009), along with Agriornis, Lessonia, Muscisaxicola, Satrapa, Xolmis, Cnemarchus, Polioxolmis, Knipolegus, Neoxolmis and Myiotheretes. Hymenops appears closely allied to Knipolegus (Ohlson et al. 2008). Two subspecies recognized: H. p. perspicillatus (Gmelin 1789) and H. p. andinus (Ridgway 1879).

The Spectacled Tyrant has two subspecies H. p. perspicillatus and H. p. andinus; the subspecies perspicillatus is distributed from southern Argentina to Paraguay, central Bolivia, Uruguay and southern Brazil. It is considered a partial migrant because part of the population in the south of Argentina moves northward during the post-reproductive period (Canevari et al. 1991). The subspecies andinus is occurs in central Chile and southern Argentina. In winter it migrates eastward across Andes from Chile to lowland Argentina.

Endemic to South America.

The Spectacled Tyrant is a flycatcher that inhabits open lands, grassy areas near water bodies, marshes, fields and pastures in southern South America. The Spectacled Tyrant has been described as a species strongly associated with wetlands and surrounding areas (Partridge 1953, Canevari et al. 1991) that nests near streams (Narosky and Salvador 1998). However, while Spectacled Tyrants have some habitat preferences for wetlands, proximity to water is not always a basic requirement for nesting, since they made use of upland grasslands without immediate presence of water on the ground (Pretelli and Isacch 2013).

The Spectacled Tyrant is considered a partial migrant because part of the population in the south of Argentina moves northward (to central Bolivia, northern Paraguay, and southern Brazil) during the post-reproductive period (Canevari et al. 1991); vagrant to southern Peru (e.g., Parker and O'Neill 1980). Spectacled Tyrant has been considered to be a resident in Buenos Aires province, Argentina (Narosky and Di Giacomo 1993), although seasonal changes in abundance suggest local movements (Isacch and Martínez 2001, Pretelli et al. 2013). In winter only a few solitary males remain on the summer ranges.

Insects. In a study in the SE Pampas region food items brought to nestlings were basically insects (94%), but also spiders (Araneidae, Lycosidae), Chilopoda, and one small frog (Hypsiboas pulchellus). Usually soli­tary. Prey pursued and captured on the ground, or during sallies from posts, bushes or reeds.

Diet of Spectacled Tyrants is composed basically of insects (Marelli 1919, Aravena 1928, Zotta 1936, Pretelli et al. 2014). At the southeast Pampas region, Argentina, Pretelli et al. (2014) identified a total of 125 prey items, representing 33 different taxa, grouped into four classes: Insecta, Arachnida, Chilopoda, and Amphibia. Based on their findings the diet of nestling Spectacled Tyrants was composed basically of Insects, which accounted for 94% of the total number of consumed prey. The orders Odonata (26%), Lepidoptera (23%), Orthoptera (20%), and Coleoptera (14%) were the most consumed prey. Of the total of lepidopterans and coleopterans, 65% and 45% were larvae, respectively. Fewer represented items offered to nestlings were Hymenoptera (5%), Arachnida (4%), Diptera (4%), and Hemiptera (2%). Chilopoda was consumed only one time. In addition, these authors recorded a striking event where a chick was fed a small frog. Frequency of prey types consumed changed along the breeding time frame. Lepidopterans were numerically the most important prey item in November, odonats in December, and orthopterans in January. Spectacled tyrants forage alone on the ground or make short sallies from posts, reeds or tall grasses in to open air.

Spectacled Tyrant performs aerial displays with mixed vocal and mechanical sounds (Straneck and Carrizo 1983, Pretelli personal observations).

In the southeastern Pampas region in Buenos Aires Province, Argentina, adult males of Spectacled Tyrant arrive to breeding grassland patches in early September and establish their territories. The territory is heavily defended against conespecific males and other species with aerial displays and persecutions. In general more than one female per territory is observed (Pretelli personal observations).

The mating system has not been studied, however since the Spectacled Tyrant shows a marked sexual dichromatism, the parental care is the exclusive concern of females, and that generally there are more than one female within each male's territory (Pretelli personal observations), it is possible that Spectacled Tyrant may be polygynous, as is the case with other grassland bird and member of the subfamily Fluvicolinae, the Strange-tailed Tyrant (Alectrurus risora) (Di Giacomo et al. 2011).

During spectacular display, male rises up to 10 m above perch, making loud bill-snap at peak, then drops straight down, wings half-closed, uttering loud cry; primaries produce buzzy whistle throughout flight; male often perches on fence posts or other exposed lookouts.

Antagonist interactions between males of Spectacled Tyrant and conspecifics, and other species are common during breeding season (Hudson 1920, Pretelli personal observations). Usually forages alone.

Little is known about the predators of Spectacled Tyrant, although raptors such as Cinereous Harrier Circus cinereus, Southern Caracara Caracara plancus, and Aplomado Falcon Falco femoralis are known to prey on adults Spectacled Tyrant (Vargas et al. 2007, Baladrón et al. 2012). In the Argentinean pampas, most of nest failures are caused by nest predation, with higher nest predation during the incubation period than during laying and nestling periods (Pretelli and Isacch 2013). However, nest survival can vary depending on the nesting site, for example nest predation in grassland patches immersed in an urban landscape matrix was 26%, while in agricultural matrix was 71% (Pretelli et al. 2015).

Oct–Jan in Argentina and Nov–Jan in Chile. In the southeastern Pampas region, Buenos Aires province, Argentina, Spectacled Tyrants breed between mid-October and late January. Nests are built within grass tussocks of Cortaderia selloana or Spartina densiflora in a period of 5–11 days. The nests are an open cup, interwoven mainly with remains of grasses. In general, nests had feathers or cow hair but some nests had no extra elements. For three nests in Argentina, external diameter 4·4–10 cm, internal diameter 3·5–6·5 cm, depth 3·7–6 cm.

Mean clutch size was 2.2 ± 0.4 eggs (range = 2–3 eggs, mode = 2 eggs). Egg color is predominantly white with brown and reddish spots generally on the wider end of the egg, but sometimes they can be an immaculate white.

The mean incubation period is 15.8 ± 0.7 days (range = 15–17 days) and the mean nestling period is 14.7 ± 0.6 days (range = 14–16 days) (Pretelli and Isacch 2013). Nestlings hatch with an average body mass of 2.4 g. In nests with one chick, young left the nest at a mean weight of 21.9 g. But when two chicks are reared together, they left the nest at a mean weight of 20.4 g. Only females build the nest, incubate the eggs and broods, and feeds and clean the chicks. Fecal sacs are swallowed or removed from the nest also by females. From 31 nests that were filmed, it was registered that the parental care was exclusive concern of females, which were in charge of building the nest, incubating the eggs and broods, and feeding and cleaning the chicks. Males were never seen at the nest (Pretelli et al. 2016). The mating system has not been studied, however since the Spectacled Tyrant shows a marked sexual dichromatism, the parental care is the exclusive concern of females, and that generally there are more than one female within each male's territory (Pretelli pers. obs.), it is possible that Spectacled Tyrant may be polygynous, as with other grassland bird and member of the subfamily fluvicoline: the Strange-tailed Tyrant (Alectrurus risora) (Di Giacomo et al. 2011).

Brood parasitism is uncommon, but it can occur. For example, from 88 nests only one contained an egg from a Shiny Cowbird (Molothrus bonariensis) (Pretelli and Isacch 2013).

Not globally threatened (Least Concern). Fairly common to common. Abundant near coastal marshes in S Buenos Aires (Argentina) in Apr. Fairly common in Los Glaciares National Park, in Argentina; occurs also in several other national parks and protected areas, especially in non-breeding season.

Because the Spectacled Tyrant has an affinity for tall grasses, the species has declined in abundance and even disappeared in vast areas of the Pampas region of Argentina, following replacement of native tall grasslands by croplands and pasturelands (Codesido et al. 2011). The reproductive performance of Spectacled Tyrant is affected by grassland fragmentation, being generally higher in large patches of grassland (e.g., natural reserves) than in small patches. However, these negative effects can be notably conditioned by the landscape matrix surrounding grasslands. In this regard, Pretelli et al. (2015) found a negative effect only when the patches were immersed in an agricultural matrix than in urban patches. For example, the nesting success was 84.4 and 86.4% lower in agricultural patches than in the reserve and urban patches, respectively. These results strongly suggest the need to retain larger areas of grassland to conserve this species and other grassland birds.

Since the Spectacled Tyrant: i) shows a marked sexual dichromatism, ii) the parental care is the exclusive concern of females, and iii) generally there are more than one female within each male's territory, it would be interesting to study the mating system of this species. On this basis, it is possible that Spectacled Tyrant may be polygynous, as with other member of the subfamily Fluvicolinae, the Strange-tailed Tyrant (Alectrurus risora) (Di Giacomo et al. 2011). Additionally, part of the population of Spectacled Tyrant in the south of Argentina moves northward during the post-reproductive period, however, little is known about this migration. This species show high breeding-site fidelity, and normally after nesting attempts (successful or not), females re-nest in the same area both within the breeding season and in consecutive breeding seasons (Mattos et al. 2011). This feature could be exploited to reveal the timing of migration and migration routes using light-level geolocators.