Birds are divided into two major groups: passerines and non-passerines. Passerines are also known as perching birds or songbirds, while non-passerines include all other bird species like raptors, waterbirds, gamebirds etc. While there are many similarities between passerines and non-passerines, there are also some key differences in their anatomy, behavior, habitat and diversity.
What are Passerines?
Passerines, or perching birds, are the largest and most diverse order of birds. There are over 6,000 species of passerines, making up around 60% of all bird species. Some examples of passerines include sparrows, finches, warblers, crows, swallows, chickadees and many more. Here are some of their key characteristics:
- Passerines have adaptations for perching including three toes pointing forward and one toe pointing backward which allows them to grasp branches and wires.
- They have a wide gape and modified tongue to aid in catching insects.
- Most passerines are small- to medium-sized birds, usually with slender bodies and short necks.
- Passerines exhibit remarkably varied plumage colors and patterns.
- They have elaborate courtship displays and songs, especially among males.
- Most passerine species build intricate, cup-shaped nests to lay their eggs.
- They are found worldwide in diverse habitats from forests to grasslands to wetlands.
What are Non-Passerines?
Non-passerine birds encompass all species that are not classified within the passerine order. There are around 4,000 species of non-passerines. Some examples include eagles, hawks, owls, woodpeckers, herons, gulls, ducks and chickens. Here are some of their characteristics:
- Non-passerines exhibit great diversity in physical traits like body size, plumage, beak shape, feet structure etc.
- Many non-passerine species have feet adapted for swimming, wading, climbing, raptoring and scratching.
- They utilize a wide range of breeding strategies from cliff-side nests to underground burrows to nest rafts.
- Courtship displays are generally less elaborate than passerines.
- Songs and calls are typically simple, without the complexity of many passerine species.
- They occupy aquatic habitats, forests, grasslands, deserts and polar regions worldwide.
Differences in Physical Features
Passerines and non-passerines diverge in many aspects of their physical features and anatomy:
Beaks
Passerines generally have thinner, more conical beaks adapted for catching insects and consuming seeds. Non-passerines display a wider range of specialized beak types like raptor hooked bills, shorebird long probing bills, toucan huge bills etc.
Feet
The feet of passerines have three toes pointing forward and one toe pointing back to facilitate perching. Non-passerines have greater variability like raptor feet with large talons, waterbird webbed feet, woodpecker feet with two toes pointing forward and two back.
Wings
Passerines exhibit more pointed wings good for short, quick bursts of flight within dense habitats. Non-passerines like shorebirds and seabirds have longer, narrower wings well-adapted for enduring long distance migration.
Tails
Passerines tend to have longer, more squared or forked tails that assist with agile flight. Non-passerines like ducks and chickens have shorter, fan-shaped tails.
Size
The passerine body plan is generally smaller and lighter. But non-passerine orders contain everything from the huge wandering albatross to tiny hummingbirds.
Plumage
Passerines display more brightly colored plumage while non-passerines like gulls and hawks tend toward more subdued grays and whites. But there are exceptions in both groups like the bright feathers of birds-of-paradise (non-passerine) and the muted tones of bushtits (passerine).
| Physical Trait | Passerines | Non-Passerines |
|---|---|---|
| Beaks | Thinner, more conical | Highly variable shapes |
| Feet | Three toes front, one back | Variable foot types |
| Wings | Short, pointed wings | Longer, narrower wings |
| Tails | Long, forked tails | Shorter, fan-shaped tails |
| Size | Small to medium | Very diverse sizes |
| Plumage | Bright, colorful | Subdued colors |
Differences in Habitat and Behavior
There are also differences in the habitats occupied and behaviors exhibited by passerines versus non-passerines:
Habitats
Passerines thrive in forested habitats. But they occupy diverse ecosystems including grasslands, shrublands, wetlands, deserts and tundra. Non-passerines are even more habitat diverse from pelagic to terrestrial to fossorial.
Migration
Many passerine species migrate long distances. But migration is also common in non-passerine shorebirds, raptors and waterfowl. Overall, a greater percentage of passerine species migrate.
Flight
Passerines excel at flying short distances within cluttered habitats. Non-passerines like swifts and shorebirds are adapted for sustained, enduring flight over long distances.
Swimming
Most passerines do not swim, with the exception of a few dipper species. Many non-passerine waterbirds are excellent swimmers like loons, grebes and cormorants.
Perching
Passerines frequently perch on branches, wires and other surfaces. While some non-passerines perch, many do not have especially adapted feet for grasping.
Food
Passerines primarily eat insects, seeds and fruit. Non-passerines have more variability in their diets including fish, aquatic invertebrates, small mammals, and carrion.
Social Systems
Passerines frequently form large flocks, especially in the non-breeding season. Gregarious flocking is seen in some non-passerines like starlings and shorebirds but is less common overall.
Vocalizations
Passerines possess elaborate vocal capabilities like birdsong. Non-passerine calls and songs tend to be simpler and less melodious.
| Behavioral Trait | Passerines | Non-Passerines |
|---|---|---|
| Habitats | Forested | Very diverse |
| Migration | Many migratory species | Some migratory species |
| Flight | Short, agile flights | Long distance flight |
| Swimming | Do not typically swim | Some excellent swimmers |
| Perching | Frequent perchers | Some perch, some don’t |
| Food | Insects, seeds, fruit | Diverse diets |
| Social systems | Gregarious, form flocks | Some gregarious species |
| Vocalizations | Elaborate songs | Simpler vocalizations |
Differences in Reproduction
There are some clear differences in how passerines and non-passerines build nests, lay eggs and care for young:
Nest Building
Passerines construct intricate, cup-shaped nests from grass, mud, lichen and other materials. Non-passerine nests show greater diversity like cliff ledges, burrows, mound nests, and no nest at all.
Clutch Size
Passerines usually lay between 2-6 eggs per clutch, rarely exceeding 7. Non-passerines like shorebirds, wildfowl and grouse often have larger clutch sizes from 6-12 eggs.
Incubation
Among passerines, females incubate eggs and brood young in most species. Non-passerine waterfowl exhibit shared incubation and brood duties between males and females.
Development
Passerine chicks are altricial, meaning they hatch blind and helpless and require extensive parental care. Many non-passerines are precocial with more developed chicks at hatch.
Fledging
Passerines fledge from nests at a young age and are still fed by parents afterwards. Non-passerine young may leave nests early (precocial) or stay for a prolonged period (altricial).
| Trait | Passerines | Non-Passerines |
|---|---|---|
| Nest building | Intricate, cup-shaped | Diverse nest types |
| Clutch size | 2-6 eggs | Variable, up to 12 eggs |
| Incubation | Mainly by female | Sometimes shared |
| Development | Altricial chicks | Precocial or altricial |
| Fledging | Leave nest young, fed after | Variable strategies |
Differences in Diversity
Passerines demonstrate far greater species diversity than non-passerines:
- There are over 6,000 species of passerines worldwide.
- In comparison, there are around 4,000 non-passerine species.
- The passerine order makes up around 60% of all bird species.
- In regions like North America, over 70% of breeding species are passerines.
- The passerine order contains over 100 different families.
- The non-passerine group has around 30 orders and 90 families.
- New passerine species are still being discovered in the Neotropics and Asia.
- There are fewer non-passerine species yet to be described.
This incredible passerine diversity arises through several factors:
- Their small body size and short generation times allow rapid speciation.
- Adaptations for flight promote dispersal to new regions.
- Complex vocal learning cultivates behavioral isolation between populations.
- Bright plumage and courtship displays drive sexual selection and reproductive isolation.
- Their dominance of forested habitats provides many ecological niches.
- Competition drives passerines to specialize on different food sources.
Passerine Families
The diverse passerine order encompasses families like:
- Finches
- Sparrows
- Warblers
- Crows and jays
- Swallows
- Wrens
- Mockingbirds
- Starlings
- Orioles
- Tanagers
Non-passerine Orders
Orders of non-passerines include:
- Falcons and eagles (falconiformes)
- Hawks and harriers (accipitriformes)
- Rails, coots and cranes (gruiformes)
- Shorebirds (charadriiformes)
- Gulls, terns and skimmers (charadriiformes)
- Albatrosses and petrels (procellariiformes)
- Parrots (psittaciformes)
- Cuckoos (cuculiformes)
- Woodpeckers (piciformes)
- Owls (strigiformes)
- Toucans (piciformes)
- Hummingbirds (apodiformes)
- Pigeons and doves (columbiformes)
- Flamingos (phoenicopteriformes)
| Diversity Aspect | Passerines | Non-Passerines |
|---|---|---|
| Species number | Over 6,000 species | Around 4,000 species |
| Percentage of all birds | Around 60% of species | Around 40% of species |
| Families | Over 100 families | Around 90 families |
| Orders | 1 order | Around 30 orders |
Conclusion
While passerines and non-passerines comprise the two main avian groups, they exhibit considerable differences in anatomy, habitat, behavior, reproduction and diversity. Passerines are specialized for perching, song production and rapid flight in forested habitats. Non-passerines occupy diverse aquatic and terrestrial ecosystems and display great variation in traits like feet, bills, plumage, nesting strategies and diet. Passerines vastly outnumber non-passerines in species diversity, making up over 60% of the world’s bird species. Their small body size, adaptability, dispersal abilities and sexual selection pressures drive this incredible passerine species richness across the globe. Though non-passerines lack passerine diversity, they fill many other ecological roles from raptors to seabirds to gamebirds. Together, the passerine and non-passerine birds represent an astonishing range of evolutionary adaptations and demonstrate the true breadth of the avian family tree.
