AnimaliaIUCN LCIn Progress Recent Sighting
Turdus grayi
Clay-colored Thrush
Bonaparte, 1838
Detailed Texts Multi-lang
The clay-colored thrush (Turdus grayi) is the National Bird of Costa Rica since 1977, declared so not for its plumage beauty — which is understated — but for the extraordinary richness and complexity of its song, which Costa Ricans have historically associated with heralding the rains at the start of the breeding season. It belongs to the family Turdidae, the thrushes and robins, and is the most well-known representative of the genus Turdus in Central America. It has a robust, medium-sized body with strong legs and a moderately long, slightly curved bill. The plumage is entirely clay-brown on the back — dark olive-brown to grayish-brown — with a whitish throat finely streaked with dark brown and a pale cinnamon-brown belly. The bill is yellowish-green to light orange, with a somewhat darker base. The eyes are brown with a bare yellowish-olive orbital ring. The legs are pinkish to grayish-brown. Sexual dimorphism is minimal and undetectable in the field. Unlike most birds with striking plumage, the clay-colored thrush compensates for its cryptic coloration with one of the richest and most varied voices of any bird on the American continent. Its range extends from southern Tamaulipas (Mexico) to northwestern Colombia and Venezuela.
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Taxonomy
PhylumChordata
ClassAves
OrderPasseriformes
FamilyTurdidae
GenusTurdus
Taxonomic AuthorityBonaparte, 1838
Ecology & Status
Origin
Native
Population Trend
Increasing
Breeding Season
--
Trophic Role
Omnivore
Recent Sightings
Yes
Habitat Summary Multi-lang
The clay-colored thrush is one of the birds with the greatest ecological niche breadth in Costa Rica, surpassed only by the great kiskadee in tolerance to human disturbance. It inhabits forest edges, open and semi-open secondary forests, wooded gardens, orchards, shade coffee plantations, urban and suburban parks, pastures with isolated trees, wooded riversides, shrublands with available leaf litter, and virtually any environment with forested or tree vegetation and accessible soil for foraging. It requires the combination of elevated perches for singing and nesting sites — trees, dense shrubs, crevices in walls — with leaf litter-covered or moist earth ground where it can search for invertebrates and fallen fruits. It is omnipresent in the Greater Metropolitan Area of Costa Rica, inter-Andean valleys, and peri-urban surroundings of all cities in the country. It is recorded from sea level to 2,800 meters altitude, being especially abundant between 800 and 1,800 meters on both slopes. It is the species that most frequently visits gardens with fruit feeders in urban and residential zones.Behaviour Multi-lang
The clay-colored thrush is diurnal and leads a markedly terrestrial and arboreal life depending on the activity. During foraging, it spends most of its time on the ground walking through leaf litter with rapid movements and abrupt stops, tossing leaves with its bill to search for invertebrates or collecting fallen fruits. For singing, resting, and monitoring its territory, it moves to high, exposed perches — canopy branches, electric cables, poles, rooftops — from where its song is audible at great distances. The male's territorial song is most intense at dawn and in the hours before rain; this association of the song with rain was what generated the popular belief that the clay-colored thrush 'calls' the rains. It does not migrate but performs seasonal altitudinal movements of up to 500-1,000 meters. It is the bird that most frequently visits fruit feeders in Costa Rican urban gardens. Its presence is so constant in the national soundscape that many Costa Ricans do not 'hear' it consciously in their daily lives — a phenomenon of perceptual habituation — until they travel abroad and notice its absence.Social Activity Multi-lang
The clay-colored thrush is primarily solitary or lives in stable monogamous pairs during the breeding season. Pairs are territorial and defend their territory through the male's prolonged song from prominent perches and pursuits of same-species intruders. Outside the breeding season, individual territories are more diffuse and small groups of 5-20 individuals may congregate in trees with high ripe fruit production. The most frequent social contact is the courtship duet between the pair — where male and female respond to each other in the same tree — and collective alarms at predators. The clay-colored thrush responds to playbacks of its own song with immediacy and aggressiveness, making it very easy to detect via playback technique during surveys. It does not regularly associate with mixed flocks of other species.Feeding Guild Multi-lang
Terrestrial-arboreal omnivore with dual strategies. It forages both on the ground and in low and mid vegetation. On the ground: walks slowly tossing leaves with its bill (leaf-turning), actively listens to detect earthworm movements, excavates with its bill in moist earth, and searches under rocks or fallen logs. In the vegetation: takes ripe fruits directly from branches and vines, occasionally captures insects in short flight. The diet includes earthworms (the most important protein fraction), soil larvae and insects, arachnids, snails, small lizards, bird eggs, soft ripe fruits of multiple botanical families, and small seeds. The proportion of each component varies seasonally: during the dry season a higher proportion of soil invertebrates; during the rainy season a higher proportion of fruits. It actively consumes from fruit feeders placed in gardens.Trophic Chain Details Multi-lang
Omnivorous primary consumer with variable trophic position. By consuming fruits and dispersing seeds it acts as a primary consumer and disperser; by consuming earthworms and soil invertebrates (organic matter consumers) it acts as a secondary consumer. Its diet includes earthworms, beetle larvae, beetles, crickets, isopods, arachnids, land snails, small lizards, eggs of other birds, and soft ripe fruits of various species (Ficus spp., Cecropia spp., Rubus spp., Solanum spp., Cestrum spp., Bursera spp., Trema micrantha). It is an important seed disperser of understory and mid-stratum plants whose seeds can be swallowed whole and defecated far from the mother tree. Its main predators are the broad-winged hawk (Buteo platypterus), sharp-shinned hawk (Accipiter striatus), the boa constrictor (Boa constrictor) for adults, and the tiger ratsnake (Spilotes pullatus). Nests are preyed upon by cats (Felis catus), rats (Rattus rattus), coatis (Nasua narica), and several arboreal snakes.Reproductive Behaviour Multi-lang
The breeding season in Costa Rica extends primarily from March to July, with the peak of nesting in April-May, coinciding with the beginning of the rainy season. The male intensifies his territorial song weeks before nesting begins. Courtship includes duet vocalizations, aerial pursuits of the female by the male, and food offerings. The female builds the nest almost alone — the male participates little — over 5 to 10 days. The nest is a deep, robust cup of roots, grass stems, leaves, mud, and diverse plant material, with the interior lined with finer fibers. It is placed in a branch fork, on a building ledge, in a clay flowerpot, or on any suitable horizontal support available, at heights of 1 to 12 meters. The clutch consists of 2 to 4 eggs — most frequently 3 — bluish-green with brownish or reddish spots. Only the female incubates for 13 to 14 days. Chicks hatch altricial and are fed by both parents with earthworms and insects for 14 to 16 days in the nest. Young reach independence 2 to 3 weeks after leaving the nest and sexual maturity at one year of age. A pair can produce up to three successful clutches per season.Physical Measures
Length (cm)
23.0 - 27.0 cm
Weight (Grams)
74 g - 95 g
Offspring per cycle2 - 4
Sexual DimorphismNo
Lifespan
Sexual Maturity
1 Years
Gestation / Incubation
13 - 14
Lifespan Estimated
Males5 - 12 Years
Females5 - 12 Years
Evolutionary Adaptations Multi-lang
Extraordinarily complex and variable vocal repertoire: males possess a repertoire of 50 to more than 100 distinct melodic phrases that they combine in variable, never identical sequences, producing a fluid and improvised song that can last hours continuously without repeating the exact same sequence. This vocal complexity — comparable in diversity to the dipper (Cinclus) and the American robin (Turdus migratorius) — develops through social learning in the first months of life, incorporating elements from the songs of other individuals of the same species heard in the neighborhood.
Terrestrial foraging behavior with 'leaf-turning': it walks slowly through ground leaf litter, tossing leaves and small objects backward with its bill to expose invertebrates hidden underneath — earthworms, beetles, larvae, centipedes, snails — and fallen fruits. This technique, combined with the ability to detect earthworm movement under the leaf litter through active listening, allows it a considerably higher capture rate of invertebrates per unit time than birds that forage only visually.
Exceptional nesting plasticity: it can nest in an extraordinary variety of substrates — from tree and shrub branches to clay flowerpots, crevices in building walls, exposed PVC pipes, outdoor lamps, and construction beams — as long as the site offers a reasonably stable horizontal platform and some degree of protection against rain and predators. This plasticity allows it to reproduce successfully in urban environments where natural nesting options are scarce.
Auditory detection of earthworms and subterranean prey: the clay-colored thrush can remain motionless for several seconds with its head tilted laterally, using its hearing to detect earthworm movement under the leaf litter at depths of up to 5 cm. When it locates the movement, it excavates with its bill at the precise spot with remarkable accuracy, extracting the earthworm on the first attempt in more than 70% of cases. This behavior has been scientifically documented as evidence of passive echolocation in terrestrial insectivorous birds.
Main Threats Multi-lang
Intensive use of pesticides, rodenticides, and herbicides in gardens and agricultural zones that eliminates earthworms, soil insects, and other invertebrates that constitute the base of the clay-colored thrush's diet. Secondary poisoning through consumption of earthworms with systemic pesticide residues is a documented mortality cause in Costa Rica, especially in coffee-growing zones of the Central Valley where carbofuran and other agrochemicals persist.
Collisions with glass surfaces in urban buildings: like the great kiskadee, the clay-colored thrush is one of the birds most frequently affected by window and glass facade collisions in Costa Rica. The male's territorial defense behavior — attacking its own reflection in the glass as if it were a rival — additionally generates repeated strikes that can cause cumulative cranial trauma and death within days or weeks even if individual impacts are not immediately fatal.
Nest predation by domestic cats (Felis catus) in urban and residential environments: given that the clay-colored thrush frequently nests at low height in gardens and house balconies, domestic and feral cats represent a significant threat to eggs and chicks. In studies of reproductive failure causes in urban gardens of San José and Heredia, cat predation has been identified as the primary cause of nest loss in 35-45% of documented cases.
Interesting Facts Multi-lang
The clay-colored thrush was declared National Bird of Costa Rica on February 26, 1977, through Executive Decree N.° 7803-A, in response to a civic initiative promoted by the Conservation League of Costa Rica and supported by the Ministry of Agriculture. The choice was controversial at the time — many expected the quetzal, much more showy, to be chosen — but the clay-colored thrush was deliberately selected as a symbol of Costa Rican national identity: a common bird with understated plumage but an exceptional voice, present in every home and landscape in the country, whose song heralds the May rains. This symbolism — beauty that lies not in appearance but in voice and everyday presence — has deeply resonated in Costa Rican popular culture.
The clay-colored thrush's song at the beginning of the rainy season — May in Costa Rica — holds deep cultural significance: Costa Ricans recognize it as the herald of the first rains and the start of the year's period of greatest agricultural and natural fertility. This association has generated a remarkable amount of Costa Rican poetry, music, and popular literature, and the clay-colored thrush's song appears in works by authors such as Aquileo Echeverría ('Romances sin rimas') and Carmen Lyra as a metaphor for Costa Rican identity, the everyday, and the genuine. The RAE includes the word 'yigüirro' in its dictionary as a Costa Ricanismo with the definition 'brown bird with a beautiful song'.
The clay-colored thrush is the American member of the evolutionary lineage that included the European common blackbird (Turdus merula) and various Palearctic thrushes, being part of one of the most successful bird genera on the planet with more than 80 species distributed on all continents except Antarctica. Its phylogenetic proximity to the European blackbird means that European immigrants in Costa Rica recognize its song as familiar and evocative, despite the two species not having 'met' in millions of years of separate evolution.
Unlike most Northern Hemisphere thrushes that migrate long distances, the clay-colored thrush is a completely resident bird in Costa Rica that never migrates. However, it performs seasonal altitudinal movements: during the dry season (December-April) it descends to lower altitudes in search of food, and at the beginning of the rainy season (May) it ascends again to higher zones where it will begin its reproductive cycle. This altitudinal movement pattern, synchronized with the arrival of the rains, is what Costa Rican popular culture interprets as the clay-colored thrush 'announcing' the rains with its song.