Austral Thrush Turdus falcklandii Scientific name definitions

The Austral Thrush is the southernmost member of the genus Turdus. This species is commonly found on the ground and in trees at the edge of forests, gardens, and agricultural land. The Austral Thrush is frequently detected by its loud whistled song and screeching calls, typical for a large thrush. The Austral Thrush has a yellow bill and legs, a dark head and grayish back, and creamy-pale underparts.

23–26·5 cm; 95–113 g. Nominate subspecies is warm brownish-olive above, with head blackish-brown to below eye, chin and throat stippled buffy and blackish, merging into ochre underparts ; bill, narrow eyering  and legs orange-yellow. Sexes similar. Juvenile is similar to adult, but with heavy buff streaking above , buffy-yellow with dark brown spots below . Subspecies <em>magellanicus</em> is smaller than nominate, colder olive-brown above with blacker head , paler below , more distinct throat pattern, female somewhat paler.

Editor's Note: This article requires further editing work to merge existing content into the appropriate Subspecies sections. Please bear with us while this update takes place.

Subspecies differ clearly in plumage. Birds from Mocha I (S Chile) described as subspecies mochae, supposedly paler and longer-billed than magellanicus, but considered insufficiently differentiated; proposed subspecies pembertoni (from Cerro Anecón Grande, Río Negro, Argentina) likewise synonymized. Two subspecies recognized.

Editor's Note: Additional distribution information for this taxon can be found in the 'Subspecies' article above. In the future we will develop a range-wide distribution article.

Open understory of dark Nothofagus forest to open forest, plantations, second growth, lighter open woodland, forest borders, riparian willows, brushy country, agricultural areas with scattered trees and hedges, and gardens; sea-level to 2150 m. In Falklands occupies variety of habitats, particularly on tussac islands and in human settlements where bushes , trees and sheds offer shelter, but also among rocky outcrops and open slopes with ferns and diddle-dee (Empetrum rubrum); greatest population density in mature tussac adjoining boulder beach with accumulated dead kelp.

Sedentary or with partial displacements. Disperses short distances in winter on mainland; in marked population of 200 individuals in Falklands, longest movement recorded was 3·6 km in just over 6 months.

Worms , snails, and arthropods (including insect larvae and pupae and, in Falklands, sandhoppers); also much fruit  , and in Chiloé (Chile) the main agent of seed dispersal of macho macho (Podocarpus nubigena). In winter months, Falklands, recorded as taking berries, especially of pigvine (Gunnera magellanica), also diddle-dee berries, cultivated currants and strawberries; also, especially in frosty weather, readily takes household scraps (bread, mutton fat). Two stomachs from Tierra del Fuego, winter, held beetles, larvae, hemipteran bugs and a blade of grass. Feeds mostly on ground , hopping about on grassy lawns and pastures, but preferring soft soil in shady places; in Falklands forages among sea-wrack. Also takes much fruit in trees. Has been seen to kill Blackish Cinclodes (Cinclodes antarcticus) and Gray-backed Storm-petrels (Garrodia nereis).

Song , from treetop well into night, variously considered “weak” and “rich”, a sustained series  of measured, muted caroling phrases, each repeated several times, juiep tiele chuii juiep chie; occasional mimicry. On Falklands (nominate subspecies), where also delivered from bush, clump, roof and even ground, varies in quality but usually a plaintive, slow succession of whistles and harsh chuckles, with loud piiuu or tii often repeated and alternating with low churring; given in spring and autumn. Subsong (Falklands) resembles muted version of full song of Eurasian Blackbird T. merula. Calls  include low huit, harsh wreet, and trrrt trrrt; in Falklands a 'purr' in agitation, chirrrp at nest, strong choyz-choyz-choyz in alarm, low buzzing chiz-chiz in courtship, deep harsh skwuk at intruders.

Song

Only the male of Austral Thrush is known to sing. The song consists of phrases of whistled and screeching syllables produced at a regular tempo, typical for a Turdus. Syllables can consist of up to four notes each, but usually are single noted. The number of syllables per phrase varies considerably depending on the situation, as explained below. Lower pitched syllables tend to be whistled and loud, whereas high pitched ones are typically screeching and more faint. Song repertoire size is variable among males, and could be an indicator of the bird's age, supporting an open-ended learner condition for the species.

Each male has his own song repertoire, and the entire population shares a number of syllables. There are variations in singing behavior, depending on the arousal level of the bird:

• Slow song: a slow, short-phrased song. On average, phrases range from 3 to 8 syllables each. Performed when the male is relaxed with no competitors or females around.
• Strong song: song delivered with a faster tempo, louder voice, and more continuous singing, making it more difficult to discriminate between phrases. Performed when a rival male is near and singing, as a vocal fight.
• Soft song: a very fast and faint song, which often includes more interspecific imitations. Performed when a fertile female approaches a male in the breeding season, and are usually delivered in persecution flights.

Mimicry Austral Thrush often imitates other sympatric species with high accuracy, though detection is cumbersome (because imitations usually are very short) and requires the listener to have high expertise in the entire vocal repertoire of local bird communities. Among the species mimicked are: Dusky Tapaculo Scytalopus fuscus, Magellanic Tapaculo Scytalopus magellanicus, Ochre-flanked Tapaculo Eugralla paradoxa, Chilean Flicker Colaptes pitius, Tufted Tit-Tyrant Anairetes parulus, White-crested Elaenia Elaenia albiceps, Austral Blackbird Curaeus curaeus, Southern Lapwing Vanellus chilensis, and Plumbeous Rail Pardirallus sanguinolentus; and birds of prey such as Austral Pygmy-Owl Glaucidium nana, Chimango Caracara Milvago chimango, Variable Hawk Geranoaetus polyosoma, and White-throated Hawk Buteo albigula.

Before the breeding season starts, the male may perform a version of soft song which is very faint and fast, with very few repetitions. If given by adults, this may serve as a vocal training for the breeding season. If given by young birds it could be part of the subsong of the species. Since this song type has been recorder only with an Autonomous Recording Unit, the age of the bird who performed it remains unknown. Nevertheless, if Austral Thrush is an open-ended learner, as suggested above, the repertoire size for the recorded soft song may indicate that it was an experimented adult male.

Song Syntax Very variable, but some consistency can be observed when analyzing sonograms of the song. In some points of southern Chile, songs phrases starts with the same syllable before switching to another "start syllable" (eg. ABCD-AEFD-AEFD-EFGH-EFHI...), adding new "middle" syllables to the phrase and repeating some of them more often than others. Some of these "favorite" syllables can be thought as leitmotiv syllables, which may allow us to identify an individual. Before switching to a new start syllable, the male usually repeats the entire last phrase.

Figures 1-3 show the song syntax of the slow song given by an adult male at Lanalhue Lake, in southern Chile: ABA'B-ACDBC-ACDBC-CD...-CGHI-CGHI.

Nevertheless, this syntax structure may not be the same for all Austral Thrush populations. More research is needed in order to determine whether song syntax and repertoire size can give information about age and if they are related to mating/breeding success.

Calls

The call repertoire of the Austral Thrush reaches at least 10 signal types. The functions of some calls are unclear since they use them in several contexts, but observations about the associated behavior are given when possible.

A. Contact call: Probably the most common call of this species, the contact call can be heard all year round. It is given when the bird seems relaxed, often when foraging. An short, low-pitched, up-slurred note, presenting non-harmonic components which indicate simultaneous action of both sides of the syrinx, which contribute to its nasal timbre. Notice the striking difference of this call when compared to its equivalent call in Falkland Islands, which may have taxonomic implications. Sound recorded by Andrew Spencer: ML77307351.

B. Alarm-arousal call: Another common call, delivered apparently when the bird is exited, often when a predator is near. Much harsher than the contact call, with a rattle-bell timbre. It can be higher-pitched and louder depending on the arousal level of the bird.

C. "See" (alarm) call: The typical "see" call that many passerines use to alert about the presence of a predator, especially hawks. This is a whistled, high pitched (around 7 kHz), slightly up-slurred, pure note, with a single, faint harmonic. This signal is very difficult to locate with accuracy.

D. Breakout or fear call: A faint, low-pitched call, hard to hear from a distance. Often released when the bird is surprised by a human -and maybe other predators?- and fly away from the ground.

See ML129833861 for examples of call types A, B, C, and D.

E. Mobbing call: Often released along with call B, the mobbing call is a high pitched series of harsh, loud notes interspersed with shrill, down-slurred whistles, often modifying tempo and amplitude. This call is given when a group of thrushes mobbing a predator, especially Austral Pygmy-Owl (Glaucidium nana).

F. Long call: The long call is composed of a series -repetition- of a single polyphonic syllable: down-slurred whistle mixed with a lower-pitched screechy, rattle-like, up-slurred note. This call is unpredictable, released very few times a day, and it's function is unknown. Sometimes the male adds this call into the song syntax, specially at dusk.

G. Long call: Similar to long call F, but this version of the long call lower-pitched and only with a rattle-like timbre. Often given at dusk, after the bird ended singing and before resting.

H. "Chatter:" The chatter is a series of nasal notes interspersed with rattle-like notes. Often given when interacting -aggressively?- with other conspecific individuals.

I. Begging call: Released by juveniles when begging for food from the adults. High pitched, faint, sometimes rattle-like call, often repeated 2 or 3 times in a row.

J. Flight call: The flight call is a high-pitched call often released by flying birds, specially at high altitude (10+ meters). This call may be present in song as well.

Additional audio recordings of vocalizations of Austral Thrush can be heard at Macaulay Library and at xeno-canto.

Bill clapping has been observed in a female when alerting the presence of an Austral Pygmy-Owl Glaucidium nana.

Sept–Feb in Chile; at least Oct–Nov in Argentina, where also a nest with 1 egg in Jan; Aug–Dec in Falkland Is; up to three broods, occasionally four in Falklands. Nest (Falklands) a large, deep cup of dry grass stems and root fibres, sometimes with wool or string, usually internally walled with mud or dung and lined with grass or horsehair, placed in sheltered crevice among rocks, atop herb-sheltered bank or large tussac pedestal, in cypress or gorse bush, or on beam in wool shed. Eggs  2–3, blue-green with brown and purple markings; 27·0–34·2 mm × 19·4–24·0 mm (n = 111 eggs) 1 Marín, M. (2015). Biología reproductiva e historia natural del Zorzal (Turdus falcklandii) en Chile central. [Breeding biology and natural history of the Austral Thrush (Turdus falcklandii) in central Chile.] Boletín del Museo Nacional de Historia Natural (Chile). 64: 81–99. Close ; incubation period 14–16 days; nestling  period around 10–11 days; interval between fledging and start of new brood as little as 12–14 days. In a study in C Chile, out of 71 eggs, 52 hatched and 29 chicks were fledged 1 Marín, M. (2015). Biología reproductiva e historia natural del Zorzal (Turdus falcklandii) en Chile central. [Breeding biology and natural history of the Austral Thrush (Turdus falcklandii) in central Chile.] Boletín del Museo Nacional de Historia Natural (Chile). 64: 81–99. Close . Of 200 ringed individuals studied over 6 years, greatest longevity was only 4·5 years.

Not globally threatened (Least Concern). Common to abundant in Chile and Argentina. In Falklands, expanded range dramatically in period 1930–1960; total population probably now c. 6000 pairs (estimate 4000–8000 pairs), highest density 4 males/ha (in mature coastal tussac). Subject to considerable predation by introduced predators, especially cats; in comparable habitats (paddocks of replanted tussac and short turf), density 2·6 males/ha where cats, rats and mice absent, but only 0·38/ha where they were present. High reproductive output appears, however, to counterbalance elevated predation effects.