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Emberizoidea

Emberizoidea is a superfamily of passerine birds, commonly referred to as the New World nine-primaried oscines, comprising approximately 832 species that are predominantly endemic to the Americas. This diverse clade includes key families such as the Parulidae (New World warblers), Thraupidae (tanagers), Icteridae (New World blackbirds), Cardinalidae (cardinals), Passerellidae (New World sparrows), and several smaller allied families like the Mitrospingidae and Zeledoniidae. The superfamily is notable for its rapid evolutionary diversification, which accounts for about 8% of all bird species and exemplifies one of the most extensive radiations within the order Passeriformes. Originating from an ancestral dispersal across from the around 15–20 million years ago, Emberizoidea underwent significant biogeographic shifts, including multiple exchanges between North and facilitated by the uplift of the approximately 3–4 million years ago. This group exhibits remarkable ecological adaptability, occupying a wide range of habitats from forests and grasslands to urban areas, with many species demonstrating high rates of behavioral and driven by factors like dispersal ability. While most species are resident or migratory within the , a few lineages, such as Old World buntings in the Emberizidae (sometimes included in broader definitions), extend into , highlighting the clade's complex evolutionary history.

Overview

Definition and Scope

Emberizoidea is a monophyletic of passerine birds within the order Passeriformes, specifically comprising the New World nine-primaried oscines, a diverse radiation characterized by the presence of nine visible or functional primary feathers in the wing, with the tenth primary typically reduced and concealed under the ninth primary covert. This morphological trait distinguishes them from other oscine groups, such as the ten-primaried lineages, and has been a key identifier since early classifications. Phylogenetically, Emberizoidea occupies a position within the suborder Passeri, forming a sister to the Old World finches (Fringillidae). The scope of Emberizoidea encompasses approximately 860 species distributed across 16 families, representing about 8% of global avian diversity (as of 2024). These birds are primarily endemic to the , with their common ancestor likely originating in the New World following dispersal from via around 15-22 million years ago; however, one major lineage, the Old World buntings (Emberizidae), represents a subsequent recolonization back to . Recent phylogenetic studies (post-2020) have refined the taxonomy, with some genera split and small families merged, such as Spindalidae and Nesospingidae into Phaenicophilidae. This biogeographic pattern underscores their distinction from Old World finches (Fringillidae), which are more closely allied to Eurasian origins and differ in plumage, bill morphology, and overall adaptations suited to temperate and boreal habitats of the . The superfamily name Emberizoidea was formally proposed in 2013 based on multilocus phylogenetic analyses that confirmed the clade's monophyly and internal structure. However, the group's core morphological and biogeographic features were initially recognized in the 19th century by ornithologists like John Gould, who described and illustrated many American species, highlighting their unique wing structure and New World affinities through works on Darwin's finches and other taxa.

Diversity and Species Count

Emberizoidea encompasses approximately 860 species of passerine birds, accounting for about 8% of global avian diversity (as of 2024). This superfamily, also known as the New World nine-primaried oscines, represents a significant portion of the songbird radiation in the Americas, with its members exhibiting remarkable taxonomic breadth across multiple families. The biodiversity within Emberizoidea is unevenly distributed among its constituent families, with several large clades driving the overall species richness. The tanagers and allies (Thraupidae) form the largest group, comprising around 390 species characterized by vibrant and diverse strategies. New World warblers (Parulidae) contribute about 132 species, many of which are renowned for their migratory habits and insectivorous diets. The New World blackbirds and allies (Icteridae) include roughly 108 species, noted for their social behaviors and vocal mimicry. New World sparrows (Passerellidae) add approximately 120 species, often adapted to open habitats, while the cardinal-grosbeaks () encompass about 54 species, featuring robust bills suited to seed-cracking. Smaller families, such as the Mitrospingidae and Nesospingidae, contribute additional diversity but with fewer species each. These groups collectively highlight the superfamily's evolutionary success in exploiting varied niches across the . Geographically, Emberizoidea exhibits peak diversity in the Neotropics, where environmental heterogeneity has fostered extensive speciation. The northern Andes stand out as a major diversification hotspot, particularly for Thraupidae, with elevated rates of lineage accumulation driven by topographic complexity and climatic gradients. High is also prominent in the , where insular isolation has led to unique radiations, such as in Parulidae and Icteridae, with many species confined to specific islands like and . These regions underscore the role of the tropics in generating the superfamily's impressive species count. Conservation challenges affect roughly 10% of Emberizoidea species, with 96 taxa classified as threatened (Critically Endangered, Endangered, or Vulnerable) according to the (as of 2019). loss and degradation in tropical Neotropical regions, including deforestation in the and Caribbean lowlands, pose the primary risks, exacerbating vulnerability for endemic and range-restricted species. Efforts to mitigate these threats emphasize expansion and restoration in biodiversity hotspots. Note that IUCN assessments are ongoing, and numbers may have changed since 2019.

Physical Characteristics

Morphology and Anatomy

Members of the superfamily Emberizoidea, comprising nine-primaried oscines, exhibit distinctive wing characterized by nine functional primary feathers per wing, differing from the ten visible primaries in most other oscine passerines. The tenth primary is reduced in size and typically concealed beneath the greater primary coverts, a trait shared across the . Bill morphology in Emberizoidea shows considerable variation aligned with feeding strategies among its families. Passerellidae () possess short, conical bills that are thick at the base, enabling efficient cracking of . In contrast, Parulidae warblers have slender, pointed bills adapted for probing to capture . Icteridae, encompassing blackbirds and , feature more robust, pointed bills suited to a broader including , invertebrates, and fruits. Skeletal adaptations include a strengthened tarsus and robust legs with sharp claws, facilitating perching on branches and ground-foraging activities prevalent in many emberizoids such as sparrows. The , birds' specialized vocal organ, in oscines of Emberizoidea possesses a complex with a cartilaginous framework, labial tissues, and intrinsic muscles that enable the generation of diverse, elaborate . Body sizes within Emberizoidea span a wide range, from diminutive warblers in Parulidae weighing 8–15 g—such as the at around 10 g—to larger in Icteridae reaching up to 550 g, as seen in the Amazonian oropendola.

Plumage Variation

Plumage in Emberizoidea exhibits remarkable diversity, ranging from vibrant hues to subtle cryptic patterns adapted to various ecological niches. In (Thraupidae), coloration often features striking red and yellow tones derived from dietary pigments, which birds modify through metabolic processes to produce vivid displays; for instance, the Scarlet Tanager's bright red male plumage results from the oxidation of yellow xanthophylls into red pigments. In contrast, sparrows (Passerellidae) typically display cryptic plumage with tan and brown streaking that provides against ground litter and arid environments, as seen in Brewer's Sparrow, where patterned feathers blend seamlessly with habitats to evade predators. Sexual dimorphism in plumage is pronounced in the Icteridae, where males often exhibit brighter, more elaborate colors than females to facilitate displays, a pattern linked to pressures that favor conspicuous male ornamentation in polygynous species. Within the Parulidae, dimorphism is generally less extreme, with males showing enhanced coloration—such as brighter yellows or blacks—compared to females, though many species retain similar overall patterns, particularly in tropical or non-migratory taxa where ancestral monochromatic traits persist. Many Emberizoidea species undergo molting cycles that produce seasonal plumage variations, particularly among long-distance migrants in Parulidae, where a prealternate molt before yields brighter alternate for territorial and purposes, while a post-breeding complete molt results in duller basic for winter and reduced predation risk during . traits further highlight this variation; juvenile warblers in Parulidae often feature heavily streaked body with brownish or grayish tones, distinguishing them from adults and aiding in identification during the brief post-fledging period. Additionally, grackles in Icteridae display iridescent feathers through , where ordered granules in barbules create shimmering blue, purple, or green effects via light interference, contrasting with matte black areas in other family members.

Distribution and Ecology

Geographic Range

The Emberizoidea superfamily encompasses a vast primary geographic range across the , extending from and in the to at the southern tip of . This distribution reflects the clade's adaptation to diverse latitudinal gradients, with species occupying temperate, subtropical, and tropical zones throughout North, Central, and . Diversity within Emberizoidea peaks in Central and , where major families such as Thraupidae () and () exhibit high , contributing to nearly 900 total species across the superfamily as of 2025. In contrast, northern regions host fewer species, primarily from families like Passerellidae () and Calcariidae (longspurs and ). Approximately 95% of Emberizoidea are endemic to the , accounting for the inclusion of Old World buntings in Emberizidae; rare exceptions occur in Calcariidae, where species like the (Plectrophenax nivalis) and (Calcarius lapponicus) have recolonized Arctic Eurasia, forming circumpolar populations. The current distribution stems from a historical expansion following a post- radiation of North American ancestors, after the clade's initial colonization of the from via the Bering during the early (approximately 15–20 million years ago). This radiation involved southward dispersals, particularly after the formation of the around 3 million years ago, which facilitated biotic exchanges between North and and drove further diversification. Contemporary threats include range contractions for some northern species due to , with observed declines in breeding densities at the southern edges of ranges for taxa like the , linked to warming temperatures and habitat alterations. These shifts highlight vulnerabilities in high-latitude populations, potentially exacerbating patterns in the core. Emberizoidea species demonstrate varied adaptations to the broad habitats spanning their range. A 2025 study on diversification dynamics in Emberizoidea emphasized the role of dispersal ability in rates across 749 species.

Habitats and Adaptations

Emberizoidea species exhibit remarkable ecological versatility, occupying diverse habitats across the that reflect their superfamily's . Tropical forests, particularly lowland rainforests and forest edges, serve as primary habitats for many Thraupidae ( and allies), where they thrive in humid environments with dense vegetation. In contrast, Passerellidae () predominantly favor open grasslands, desert scrub, arctic barrens, and tidal marshes, adapting to arid and temperate open landscapes. Wetlands, including marshes and savannas, are key for Icteridae (troupials and allies), which exploit seasonally flooded grasslands and coastal areas. Parulidae () often inhabit high-altitude shrublands, boreal forests, and layers of woodlands, spanning from shrubby old fields to mature forest interiors. Physiological adaptations enable Emberizoidea to endure extreme conditions within these habitats. In Andean high-altitude species, such as the rufous-collared sparrow (Zonotrichia capensis) in Passerellidae, hemoglobin polymorphisms vary clinally with elevation, though functional tests indicate no significant changes in oxygen-binding properties for tolerance at elevations exceeding 4,000 meters. Microhabitat specialization further refines habitat use, reducing . Parulidae species frequently in the forest understory, exploiting low vegetation strata for resources in shaded, humid layers. Conversely, Thraupidae often occupy the canopy and mid-story of tropical forests, where brighter light and fruit availability align with their arboreal lifestyles. To cope with seasonal climate variability, many Emberizoidea employ behavioral adaptations like altitudinal , shifting elevations to track optimal conditions. In montane regions, such as certain Andean warblers and sparrows descend to lower altitudes during harsh winters, enhancing to fluctuations and scarcity. This flexibility underscores the superfamily's broad ecological tolerance, from tundras to equatorial lowlands.

Behavior

Foraging and Diet

Members of Emberizoidea exhibit a diverse spectrum of diets tailored to their ecological niches, ranging from predominantly insectivorous to granivorous and omnivorous habits across families. In Parulidae ( warblers), the diet is primarily insectivorous, consisting mainly of and other small such as spiders, with arthropods making up the bulk of consumption year-round, though some species like the occasionally incorporate seeds. Passerellidae () are largely granivorous, relying on seeds from grasses and weeds as a dominant food source, particularly outside the breeding season, supplemented by fruits and . Icteridae (blackbirds and allies) display omnivorous tendencies, incorporating , fruits, seeds, , and occasionally small vertebrates like or eggs into their diet. Thraupidae () show varied feeding, often favoring fruits and but also consuming and seeds depending on availability. Foraging techniques within Emberizoidea are specialized to exploit these dietary resources efficiently. Parulidae typically employ , methodically searching and picking from foliage, branches, and leaf , with occasional hovering or short sallies to capture prey. In Passerellidae, ground-probing and scratching are common, where birds use their bills and feet to uncover and buried in or , often in open grassy areas. Icteridae utilize a mix of techniques, including ground foraging for and , foliage for fruits and arthropods, and aerial hawking in species like grackles to snatch flying mid-air. Tool use is rare but documented in Thraupidae, notably in the Woodpecker Finch, which employs twigs or cactus spines as probes to extract larvae from or crevices. Seasonal shifts in are prevalent among Emberizoidea, driven by nutritional demands and resource availability. During the , many increase consumption for high-protein needs to support nestling growth, as seen in Passerellidae where dominate over , and in Parulidae where caterpillars and other soft-bodied peak in intake. In winter or non- periods, reliance shifts toward more readily available and fruits, reducing the proportion of ; for instance, Savannah Sparrows consume mostly larval and adult in summer but switch to small and spiders in winter. These adaptations ensure across seasons, with bill morphology facilitating the transitions, as conical bills in granivores aid seed cracking while slender bills in enable precise probing.

Reproduction and Breeding

Members of Emberizoidea display a range of breeding systems, with most species in Parulidae forming pairs that are territorial during the breeding season. Similarly, Passerellidae species, such as sparrows and towhees, typically breed in socially pairs with biparental involvement in territory defense. In Icteridae, mating systems vary, including in orioles but in species like red-winged blackbirds, where males maintain multiple mates. Thraupidae are generally monogamous, though pair bonds may be seasonal and less intense in some tropical species. Nest architecture differs markedly across families, reflecting adaptations. Parulidae warblers build open cup nests from grasses, bark, and fibers, typically placed in or shrubs 1–10 m above ground. Passerellidae often construct similar cup nests on or near the ground in dense vegetation, using grasses and roots for concealment. Icteridae nests vary widely, from the woven pendant structures of suspended from branch tips to bulky grass domes of meadowlarks in marshes. Thraupidae nests are compact open cups of fine material, sited in foliage or vines. Clutch sizes in Emberizoidea generally range from 3 to 5 eggs, though some Parulidae species lay up to 6 during migration-influenced breeding. , lasting 11–14 days, is performed solely by the female in most families, including Thraupidae and Parulidae, with eggs hatching asynchronously over 1–2 days. Parental care emphasizes nestling provisioning, with biparental feeding common in Passerellidae sparrows and Parulidae warblers, where males deliver to support rapid growth. Thraupidae also exhibit biparental feeding, while Icteridae show variable involvement, with males contributing more in monogamous pairs like orioles. Young fledge after 10–20 days, remaining dependent on parents for several weeks post-fledging to learn skills.

Evolution

Origins and Diversification

The superfamily Emberizoidea originated through a dispersal event from Eurasian ancestors into via the during the early , approximately 20 million years ago (Ma), marking the stem age of the . This migration facilitated a subsequent radiation in , where the crown group began diversifying around 14–15 Ma, leading to the accumulation of over 800 species primarily in the . Recent molecular clock analyses confirm this crown age estimate in the range of 14–20 Ma. The initial diversification was characterized by rapid events, establishing the foundational lineages of this diverse group. A pivotal event in the Neotropical diversification of Emberizoidea occurred around 12-10 Ma, involving a dispersal to the that isolated endemics, such as those in the family Teretistridae, from mainland clades. Concurrently, the South American tanager-cardinal clade (encompassing Thraupidae and ) underwent early invasion and radiation, with ancestral dispersals southward predating the final closure of the around 3 Ma. This split contributed to the clade's expansion into tropical habitats, enhancing overall species richness. The primary drivers of Emberizoidea's adaptive radiations included vicariance associated with the Miocene-Pliocene uplift of the , which created topographic barriers and new ecological niches, particularly influencing diversification in lineages. Climate oscillations during the and subsequent further promoted by altering habitats and migration patterns, enabling colonization of diverse environments from temperate to tropical zones. Later in the evolutionary history, select lineages within Emberizoidea recolonized , with Emberizidae dispersing back across around 12 Ma during the . These back-migrations underscore the bidirectional biogeographic dynamics of the superfamily.

Fossil Evidence

The fossil record of Emberizoidea remains sparse, particularly prior to the , owing to the poor preservation potential of small birds, whose delicate bones rarely fossilize completely. The earliest definitive fossils attributed to the are from North American deposits, including the sparrow-like Palaeostruthus hatcheri from late sediments near , , dating to approximately 10 million years ago; this specimen represents a stem and provides the oldest direct evidence for the group's presence in the . Key Pliocene specimens include relatives of Icteridae from , such as humeri and other postcranial elements of Sturnella (meadowlarks) recovered from early sites like the Formation, morphologically similar to modern S. magna and indicating the diversification of blackbirds in subtropical environments by around 4–5 million years ago. In the Pleistocene, records become more abundant, with diverse emberizoid remains from sites like the in , encompassing genera such as Euphagus (rusty blackbirds) and various passerellids (), reflecting adaptation to late woodlands and grasslands. Notable fossil sites contributing to this record include the Formation in and , which, while primarily Eocene, preserves early stem passerines that contextualize the later radiation of Emberizoidea, and the , offering one of the most complete Pleistocene avifaunas with over 140 bird species, including multiple emberizoid taxa trapped in asphalt seeps. Despite these finds, significant gaps persist in the pre- record, with no unambiguous emberizoid fossils before ~15 Ma; molecular clock analyses, calibrated using these Miocene specimens, estimate the crown-group age of Emberizoidea at approximately 14 million years ago, aligning with inferred diversification during the mid- climatic optimum.

Taxonomy

Classification History

The classification of Emberizoidea traces back to the , when , buntings, and related were frequently grouped with buntings under broad families such as Emberizidae or Fringillidae, resulting in significant taxonomic confusion due to superficial similarities in bill structure and . In the mid-20th century, ornithologist Harrison B. Tordoff advanced the understanding of these birds by identifying the New World nine-primaried oscines as a cohesive distinguished by specific skeletal features, such as the reduction of the tenth primary feather and shared palatal morphology, thereby separating them from other oscine passerines. This morphological recognition laid the groundwork for treating the group as distinct from both finches and other New World songbirds. Alexander Wetmore's comprehensive 1960 classification further formalized this clade within Passeriformes, positioning the nine-primaried oscines as a major suboscine assemblage encompassing families like Parulidae (wood warblers), Icteridae (blackbirds), Thraupidae (tanagers), Cardinalidae (cardinals), and , emphasizing their shared anatomical traits. The advent of molecular techniques revolutionized the in the late , with Charles G. Sibley and Jon E. Ahlquist's DNA-DNA hybridization analyses confirming the of the New World nine-primaried oscines and proposing their elevation to parvorder status as Emberizida within the suborder Oscines. Sibley and Burt L. Monroe Jr. elaborated on this in their 1990 taxonomic compendium, outlining the group's internal structure with multiple tribes and subfamilies while highlighting its divergence from Eurasian lineages. Recent genomic studies have driven further refinements, including expansions of family boundaries such as the incorporation of many emberizid-like genera into a broadened based on multi-locus phylogenies. The Ornithological Congress (IOC) recognizes the superfamily designation Emberizoidea following molecular insights from 2019, for this monophyletic radiation of approximately 832 species.

Current Families and Phylogeny

Emberizoidea currently encompasses 15 families of New World nine-primaried oscines, reflecting a monophyletic radiation confined to the Americas and adjacent islands (Old World buntings in Emberizidae belong to the sister superfamily Passeroidea). These families vary markedly in size and diversity, with core groups including Thraupidae (370 species of tanagers), Parulidae (120 species of wood-warblers), Passerellidae (120 species of New World sparrows), and Icteridae (110 species of blackbirds, orioles, and allies). Smaller families include Zeledoniidae (1 species, the wrenthrush), Mitrospingidae (4 species of tanager-like finches), Phaenicophilidae (4 species of palm-tanagers), Nesospingidae (1 species, the Puerto Rican tanager), Spindalidae (4 species of spindalises), Icteriidae (1 species, the yellow-breasted chat), Teretistridae (2 species of Cuban warblers), Cardinalidae (13 species of cardinals and grosbeaks), and Calcariidae (6 species of longspurs and snow buntings). The remaining families—Rhodinocichlidae (1 species, the rosy thrush-tanager) and Calyptophilidae (2 species of chat-tanagers)—further highlight the superfamily's emphasis on small, often inconspicuous taxa adapted to diverse habitats. As of IOC World Bird List v15.1 (2025), the total has increased to approximately 890 species due to recent taxonomic splits. Phylogenetic relationships within Emberizoidea have been resolved through multilocus analyses, revealing a basal between the passerellid-calcariid (including Calcariidae, Passerellidae, and Rhodinocichlidae) and the more diverse parvuld-tanagroid (encompassing Parulidae, Icteridae, Thraupidae, , and the minor and Central American families such as Zeledoniidae, Teretistridae, Nesospingidae, Spindalidae, Phaenicophilidae, Mitrospingidae, and Calyptophilidae). Within the parvuld-tanagroid , Thraupidae and emerge as sister taxa to the remaining lineages, a relationship supported by shared morphological traits like robust bills and vibrant plumage in many species. This structure is summarized in the time-calibrated from Oliveros et al. (2019), which integrates data across all major lineages and underscores Emberizoidea's rapid diversification during the . Subfamily-level details further refine this classification; for example, Parulidae is largely monotypic at the subfamily level, with all species assigned to Parulinae, reflecting their uniform adaptations for insectivory and foliage-gleaning. In contrast, Icteridae includes debated subfamilies like Icterinae (true blackbirds) and Agelaiinae (meadowlarks), with some studies questioning the family's overall due to paraphyletic placements of certain genera relative to Parulidae, though recent analyses affirm its integrity. Similarly, Thraupidae encompasses multiple subfamilies such as Thraupinae and Coerebinae (bananaquits), highlighting its polyphyletic historical treatments now unified under molecular evidence. Genomic investigations, including whole-genome sequencing of representative taxa, reinforce Emberizoidea's exclusivity to the , tracing its origins to a single colonization event from via around 20-25 million years ago, with subsequent radiations confined to American continents and adjacent islands. These studies, building on ultraconserved element (UCE) datasets from over 4,000 loci across 137 families, confirm the clade's and lack of sister groups beyond basal dispersals.

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