Dinosaur

A member of the dinosaur lineage, including birds. Restricting the word to extinct nonavian forms excludes descendants.

Megalosaurus is a genus of extinct predatory theropod dinosaurs known from Jurassic remains in England. Fossil jaw and limb material from Stonesfield contributed to its early recognition. William Buckland published a description in 1824, before the later name Dinosauria had been introduced. ^[ref]

The preserved lower jaw illustrates how specific observations constrain reconstruction. Serrated, blade-like teeth support a meat-eating interpretation, while imaging can reveal replacement teeth hidden within the bone. A fossil specimen and a complete life reconstruction contain different amounts of direct evidence: posture, missing anatomy and evolutionary relationships require comparisons beyond the isolated jaw.

A member of the theropod lineage of dinosaurs, within which birds are nested. The hands and integument of nonavian relatives inform comparisons of avian origins.

A name used for a more restricted avian-lineage clade than Panaves. Definitions have included a branch-based bird-versus-deinonychosaur rule and an apomorphy-based flight rule; the definition must be specified in comparative work.

A nonavian tyrannosauroid dinosaur represented by skeletons with preserved filamentous feathers.

A member of the avian lineage of theropod dinosaurs. The extent of the named group can differ between crown-based and broader fossil usages.

The white-rumped munia, Lonchura striata, is a songbird whose domesticated descendant is the Bengalese finch. The two forms are useful for studying how behavior differs between a wild lineage and a lineage maintained under domestication. A domesticated form is not automatically a separate species.^[ref]

A 2021 experiment compared feeding when an unfamiliar object was present. Groups of white-rumped munias were less likely to feed and waited longer than Bengalese finch groups under the novel-object conditions. This was interpreted as a difference in neophobia, avoidance of unfamiliar things. The wild-caught white-rumped munias had already spent more than a year in laboratory housing before testing, so wild origin and immediate testing environment were distinct features of the design.^[ref]

A longer feeding delay does not alone identify a uniquely inherited fear mechanism. Prior experience, housing and the social group used in a test can affect behavior. The comparison supplies a measured behavioral contrast, while the full evolutionary explanation requires evidence beyond the contrast itself.

The Seychelles warbler, Acrocephalus sechellensis, is a small songbird of the Seychelles islands. Its natural geographic restriction is an example of endemism. Long-term field monitoring has made it a useful subject for studying cooperative breeding, in which additional individuals help care for young.^[ref]

In this species, older offspring can remain with their parents and help defend the breeding area or feed younger offspring. That observation raises a causal question: do helpers increase reproductive success, or do productive breeding areas simply produce and retain more helpers? Jan Komdeur's 1994 removal experiment addressed this by reducing groups and controlling comparisons for area quality, initial group size and breeder age.^[ref]

One additional caregiver improved parental reproductive success under the tested conditions. Two or more in medium-quality areas could instead reduce success relative to one. Competition over reproduction or resources were proposed explanations, rather than established universal causes. The experiment therefore shows why counting helpers alone cannot establish a steadily increasing benefit: the effect depends on ecological and social context.^[ref]

The Bengalese finch is a domesticated songbird derived from the white-rumped munia, Lonchura striata. Research papers often designate it Lonchura striata var. domestica. The name identifies a domesticated form, rather than by itself establishing a separate wild species. Its learned birdsong makes it useful for experiments on auditory feedback and behavioral change.^[ref]

In 2007, Evren C. Tumer and Michael S. Brainard tested whether small variations in otherwise stable adult birdsong could support learning. A computerized system monitored the pitch of selected song elements and disrupted auditory feedback for a selected subset of renditions. The birds shifted the targeted pitch to avoid the disruption, while other song features were relatively preserved. Delaying the feedback prevented the adaptive shift in the reported comparison.^[ref]

For an illustrative version of the logic, suppose feedback is disrupted only when one chosen song element falls below a preset pitch. Later singing above that threshold would reduce disruption. The key comparison is the distribution of that element before and after contingent feedback, together with appropriate feedback controls. A shift need not mean the bird acquired an entirely new song; it can reveal adjustment of one feature within a practiced behavior.

Passeriformes is the order of birds commonly called passerines or perching birds. Its major living branches include Acanthisittidae, the New Zealand wrens; Tyranni, the suboscines; and Passeri, the songbirds. Thus songbirds form an important branch within Passeriformes, rather than being an exact synonym for the entire order.^[ref]

The group illustrates how evolutionary histories are tested with independent kinds of evidence. A 2019 study analyzed 4060 nuclear DNA regions across 137 passerine families and used 13 fossils to calibrate the resulting phylogenetic tree. DNA comparisons estimate relationships and relative amounts of change; a fossil supplies an age constraint, rather than a complete date label for every branch.^[ref]

An illustrative consequence is that two visually similar birds need not be closest relatives: similar ways of feeding or moving can favor similar shapes. Conversely, related branches can evolve very different appearances. A well-sampled phylogenetic tree lets investigators ask whether a repeated feature was inherited once or arose independently, while making explicit which taxa and genes were compared. The 2019 reconstruction tested explanations for diversification instead of assuming that a rise in global temperature must automatically produce a matching rise in speciation.

Acanthisittidae is the New Zealand wren family, a major branch of Passeriformes distinct from both Tyranni and the songbirds of Passeri. The rifleman is one representative. The familiar word “wren” is not by itself evidence that these birds belong with every other small bird given that common name.^[ref]

The rifleman searches trunks and branches for small invertebrates and makes short flights between feeding sites. Such observations describe how a living member uses its environment; they are a different kind of evidence from the DNA comparisons used to establish the family's evolutionary position.^[ref]

A useful classification test therefore asks two separate questions: does another bird share a similar body shape or feeding habit, and does it share the ancestry indicated by a phylogenetic tree? Similar ecological demands can produce similar appearances in different branches. Broad genomic sampling places Acanthisittidae in the passerine tree without defining the group merely by small size, a short tail or an English common name.

The rifleman, Acanthisitta chloris, is a small New Zealand forest bird in Acanthisittidae. It has short wings, a very short tail and a slender, slightly upturned bill. Males and females differ in plumage: males have green upperparts, while females are more brown and speckled, an example of sexual dimorphism.^[ref]

Its way of feeding is closely tied to the forest's surfaces. A rifleman searches tree trunks, bark and foliage for small invertebrates and usually moves between feeding sites by short flights. Watching whether a bird probes beneath bark, picks prey from a leaf or catches it in the air distinguishes different foraging actions rather than treating all insect eating as the same behavior.^[ref]

The species also illustrates cooperative breeding. Related young can help feed a later brood alongside the breeding pair. To describe this correctly, an observer must identify individuals and record who delivers food: counting visits to a nest alone cannot distinguish parental care from help supplied by other group members. Such observations connect the family group to the survival of young without assuming that every bird at a nest is a parent.^[ref]

Tyranni, the suboscines, is a major branch of Passeriformes distinct from Acanthisittidae and from the songbirds of Passeri. It includes the eastern phoebe. The taxonomic distinction makes comparisons of vocal development especially informative: a pattern established in an oscine songbird need not apply to every passerine.^[ref]

A 1991 experiment tested whether the eastern phoebe required hearing its own voice to develop normal song. Four birds were collected as nestlings and hand-reared; before they began singing, they were deafened. Their later songs were compared with those of intact laboratory birds and wild males and were judged normal. In these tested birds, normal song development therefore did not require auditory feedback.^[ref]

The experiment separates a developmental requirement from a correlation: hearing song and producing song normally occur together, but removing feedback tests whether it is necessary. The result concerns the tested species and conditions. It should not be generalized into a claim that no member of Tyranni can ever modify a vocalization through learning.

The eastern phoebe, Sayornis phoebe, is a North American flycatcher belonging to Tyranni, the suboscine branch of Passeriformes. It often watches for flying insects from a low perch, then makes a short flight to capture prey. Sheltered ledges, including those on bridges and buildings, provide nesting sites. Feeding behavior and nest placement help identify the living species alongside its appearance and voice.^[ref]

Its vocal development provides a controlled test of learning. In a 1991 study, four nestlings collected at 10–12 days were hand-reared and deafened at about 35 days, before they began singing. Their later songs were judged normal in comparison with wild males and intact laboratory birds. The tested birds could therefore develop the species-typical song without auditory feedback from their own voices.^[ref]

The result is narrower than saying that the brain or experience has no role in singing. It tests whether intact hearing during this developmental interval is necessary for the measured song pattern. Comparing it with a songbird experiment in which removing auditory experience disrupts song makes the experimental question clear: similar adult behavior can arise through different developmental requirements.

A songbird, or oscine, is a bird of Passeri, a major branch of Passeriformes. The name denotes evolutionary membership, rather than a judgment about whether a particular call is melodious. The chaffinch is one familiar example. Relationships among these birds are studied using DNA and phylogenetic trees, alongside their anatomy and behavior.^[ref]

Songbirds provide particularly clear experiments on learning. In W. H. Thorpe's chaffinch experiments, birds raised without normal song exposure developed simpler songs, whereas birds with early experience could retain much more normal patterns. An apparatus called the Song Tutor replayed constructed sequences of notes, letting the investigator change what a juvenile heard rather than merely observe wild adults. Some artificial patterns were learned, provided their sound characteristics were sufficiently appropriate.^[ref]

The comparison separates three questions: what vocal patterns a bird can physically produce, what experience supplies, and when that experience is effective. A sensitive period means that the timing of exposure matters. These results establish a role for experience in the tested species; they do not imply that every songbird learns the same repertoire at the same age.

The chaffinch studied in classic song-learning experiments is Fringilla coelebs, a songbird. Its male song combines inherited organization with details acquired through learning.

In his 1958 experiments, W. H. Thorpe compared wild birds, juveniles isolated after time in the wild, and birds hand-reared in auditory isolation from the fifth day of life. The early-isolated birds produced much simpler songs; birds isolated only in their first autumn retained nearly normal patterns. Groups of early-isolated birds could develop elaborate but abnormal shared songs by hearing and copying one another.^[ref]

A playback apparatus called the Song Tutor presented artificial patterns assembled from chaffinch notes. Birds learned some patterns when their tonal qualities were sufficiently similar to normal song. These results distinguish inherited dispositions from the auditory experience needed for local song details. Learning was also concentrated in a sensitive period, principally within the first thirteen months in these experiments.^[ref]

The common nightingale, Luscinia megarhynchos, is a songbird associated with dense low vegetation in its breeding habitat. Its familiar song and its habitat requirements provide different ways to study the same organism: vocal behaviour concerns communication, while settlement and movement reveal responses to vegetation structure.

A woodland experiment created eight paired areas in which deer were either excluded or allowed to browse. Territory mapping and radio tracking showed strong nightingale use of the protected regrowth. ^[ref] Tracked birds spent 69% of their time in the protected 6% of the study area. This links browsing to habitat use through an intervention, rather than inferring the mechanism solely from parallel population trends.

A toothed latest Cretaceous bird outside the living-bird crown group. Its preserved pterygoid bone supplies evidence for a mobile palatal arrangement before the crown divergence.

A toothed Late Cretaceous bird outside Aves in crown usage, important for comparisons of the avian skull.

A Late Jurassic avian-lineage theropod dinosaur outside the living-bird crown group under standard relationships.

Used here for the crown group of birds: the last common ancestor of living palaeognaths and neognaths and all descendants. Broader historical definitions also occur and should be stated explicitly.

The crown-bird lineage containing Galloanserae and other living birds outside Palaeognathae. Taxonomic membership and possession of a particular mobile palate are different claims.

A sparrow is a small perching bird; the common name is applied to more than one evolutionary group. An ecological description such as seed eating should therefore be separated from a claim that every bird called a sparrow belongs to one narrow lineage.

The clade containing landfowl and waterfowl.

Waterfowl are birds of the duck, goose and swan group. Together with landfowl they form Galloanserae. Aquatic habits are common, but the evolutionary grouping is more specific than all birds that live near water.

Landfowl are birds of the chicken, pheasant and related group. They form one branch of Galloanserae, alongside waterfowl. The name identifies a lineage rather than every ground-feeding bird.

The crown-bird lineage containing ostriches, emus, kiwis, tinamous and relatives. Its palaeognathous palate is an anatomical specialization, not evidence that its members are ancestors of neognaths.

A tinamou is a palaeognath bird native to the Americas. Tinamous can fly, showing that membership in this evolutionary group is not equivalent to flightlessness.

An ostrich is a large flightless palaeognath bird with strong running adaptations. Its reduced flight apparatus and powerful hindlimbs illustrate evolutionary modification of the shared avian body plan.

The great tit, Parus major, is a small perching bird widely studied in ecology and animal behaviour. Observations of breeding, foraging and survival can connect variation among individuals to their changing environment.

A corvid used in studies of food caching and experience-dependent cache protection.

A corvid, including Corvus corax, used in studies of social information and caching.

A radiation of Galápagos and nearby finches important in studies of ecological divergence, song and hybridization.

Geospiza conirostris is the large cactus finch, a member of Darwin's finches. Its feeding structures provide material for studying the relation between ecology, inherited variation and evolutionary change.

Geospiza fortis is the medium ground finch, one of Darwin's finches. Variation in its beak and food resources has made it an important system for studying natural selection across environmental changes.

The owl called Tyto alba in the cited sibling-negotiation experiments.

The bird studied in experiments on flexible deceptive alarm mimicry.