Vertebrate Zoology: A Study Guide - T. A. Dauda 2014

Multicellular Animals
Class Aves
Superorder Carinatae - Order Passeriformes

This is the largest order of birds (Figs. 48 and 49), comprising about 5,000 species—more than half of all modern birds. Their appearance and size vary greatly. Passerines have four toes on each FOOT, with three pointing forward and one backward. These birds are known for building meticulous nests where helpless hatchlings emerge. Many species are closely associated with trees and shrubs. Over a thousand species (such as broadbills, suboscines, and pseudo-oscines) inhabit North and South America, as well as Australia. The vast majority of the order, however, consists of songbirds, which are widespread. Among them, about 312 species live in our country.

The most common representatives belong to the following families: Hirundinidae (swallows: barn, wire-tailed, sand martin); Alaudidae (larks: skylark, crested lark, lesser short-toed lark); Motacillidae (wagtails: yellow and white; pipits: tree, tawny); Laniidae (shrikes: great grey, red-backed); Bombycillidae (waxwing); Cinclidae (dipper); Troglodytidae (wren); Turdidae (thrushes: mistletoe thrush, fieldfare, song thrush, redwing; northern wheatear, whinchat, common redstart, common nightingale, European robin); Sylviidae (warblers: willow warbler, chiffchaff, wood warbler; reed warblers: garden, marsh; marsh warbler; whitethroats: garden, blackcap, common whitethroat, goldcrest); Muscicapidae (flycatchers: spotted and European pied); Paridae (tits: great tit, Eurasian blue tit, coal tit, crested tit, marsh tit); Sittidae (Eurasian nuthatch); Certhiidae (Eurasian treecreeper); Emberizidae (buntings: yellowhammer, reed bunting, rustic bunting); Fringillidae (hawfinch, European greenfinch, European goldfinch, Eurasian siskin, common linnet, common redpoll, Eurasian bullfinch, common rosefinch, red crossbill, common chaffinch, brambling); Ploceidae (sparrows: house, Eurasian tree); Sturnidae (starlings: common, rosy); Oriolidae (golden oriole); Corvidae (common raven, hooded crow, rook, Eurasian jackdaw, spotted nutcracker, Eurasian jay, Eurasian magpie).

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Fig. 48 Representatives of the order Passeriformes:

1 — song thrush; 2 — red crossbill; 3 — European pied flycatcher; 4 — red-backed shrike; 5 — common redstart.

Fig. 49 Representatives of the order Passeriformes:

1 — barn swallow; 2 — Eurasian bullfinch; 3 — Eurasian nuthatch; 4 — white wagtail; 5 — great tit; 6 — coal tit; 7 — crested tit; 8 — marsh tit; 9 — Eurasian blue tit.

The diversity and wide distribution of passerines across various habitats have led to the evolution of a rich array of ecological adaptations to different living conditions. For instance, swallows spend most of their time in the air, diving, looping, gliding, and tumbling. This is facilitated by their elongated, streamlined bodies and sharp, powerful wings. They land on the ground very rarely and reluctantly. They build their nests on cliffs, walls, or under house eaves. Typically, these are neat structures made of straw, clay, and soil, cemented with saliva. They feed on insects, which they catch high in the air with a wide-gapped bill fringed with bristles at the sides.

During the nestling-feeding period, swallows may visit the nest up to 600 times a day, bringing back several insects each time.

Larks feed on insects, but unlike swallows, they forage on the ground surface. Therefore, they arrive very early, as soon as bare patches of ground appear through the snow. Larks can often be heard singing as early as late March. A lark begins to sing while ascending (sometimes to a height of 150 m), and the higher it flies, the more resonant its voice becomes. As it descends, the lark sings in short bursts and falls silent 20 meters above the ground, before soaring upward once again. The male sings while the female stays on the ground. Larks begin to nest after green vegetation appears. They build their nests hidden in the grass.

Their chicks are altricial. After leaving the nest, the parents continue to feed the flightless young on the ground. The complete feeding period lasts about 3 weeks. There are two clutches per summer.

Wagtails are slender little birds with long tails that constantly bob up and down. They arrive very early in spring, prompting the folk saying: "The wagtail arrives and breaks the ice with its tail." These birds feed on insects found on the soil surface. They nest on the ground, under tree roots, beneath brushwood piles, or occasionally in tree hollows. The clutch contains 5–6 eggs. Both parents incubate for 2 weeks and spend an equal amount of time feeding the young.

Shrikes are renowned as exceptional mimics of various bird songs. Their claws and beaks are curved and powerful, much like those of birds of prey. Shrikes feed on insects, but can also catch mice, lizards, and other small animals. Having caught their prey, a shrike impales it on a thorn or plant spine, which makes it easier to handle and serves as a way to store food. Their nests are neatly built. The clutch consists of 4–7 eggs. Incubation is carried out alternately by both parents or by the female alone, while the male guards and feeds her. Both parents feed the young for 3 weeks.

Thrushes are insectivorous birds, though in autumn they eat berries and often forage on the ground. They build their nests in trees quickly, within 3 to 5 days, lining the interior walls with clay. They hop rather than run along the ground. They are magnificent singers, though the nightingale, another member of the thrush family, is considered the finest vocal soloist. Their appearance is rather modest: nightingales are slightly larger than sparrows, with long legs and large dark eyes, and a brownish-grey plumage. They are very timid and cautious. They nest on the ground, sheltered by bushes or dense grass. The clutch contains 4–6 eggs, and the chicks are fed on insects.

Nuthatches are fascinating for their foraging technique. They are exceptional tree-climbers, meticulously searching every crevice, opening, and crack to extract insects and their larvae.

A representative of the weaverbird family, the house sparrow is the world's most familiar bird, typically living in close proximity to humans. House sparrows live in flocks and nest wherever they can find a spot: under a roof or eaves, behind a window frame, inside an old drainpipe, or in a tree cavity. Their chicks are fed a mixed diet dominated by insects. Adults have a varied diet consisting of seeds, berries, grains, flower buds, and food waste, alongside insects. It is estimated that a flock of 1,000 sparrows destroys up to 8 kg of weed seeds in a month. Over 2 weeks of feeding chicks, the parents bring about 1–1.5 kg of insects to the nest. Worldwide, sparrows are believed to destroy tens of millions of tons of insects. Additionally, they help clear our towns and villages of minor debris.

The common starling is one of the few birds that readily occupies artificial nesting boxes (birdhouses) specifically put up to attract birds to gardens, parks, and orchards. In the wild, they inhabit forests and nest in tree hollows. A clutch contains 5–7 eggs. Outside the breeding season, they gather in flocks. Their song includes mimicry of other birds, and their call is harsh and grating. They forage mainly on the ground, occasionally in trees. They are exceptionally beneficial due to their destruction of vast numbers of harmful insects. For instance, the rosy starling, which inhabits steppe and desert plains, feeds primarily on locusts. A single starling can consume up to 200 g of pest insects a day—2.5 times its own body weight.

Golden orioles have a robust build and are slightly larger than starlings. The males have a striking plumage dominated by bright yellow, making this one of the most beautiful birds in our forests. They are among the last to return in spring, arriving only when the foliage is dense enough to conceal them. The golden oriole sings brilliantly, its song resembling the sound of a flute. However, it can also produce harsh, cat-like calls. It builds its nest at the very tip of a tree branch, keeping the chicks safe from predators. The clutch has 4–5 eggs. Incubation is performed mainly by the female, with the male occasionally relieving her. Adult orioles and their chicks feed primarily on insects, including agricultural pests.

The order Passeriformes includes resident birds (which live in the same areas year-round) and nomadic birds (which occupy a territory only during the breeding season and wander in search of food the rest of the time). There are also migratory birds: they appear in their breeding grounds in spring, raise offspring in the summer, and fly off to warmer regions in autumn.

Bird Migration

Historically, bird migration developed over millennia as a consequence of the establishment of seasons on Earth. Today, the primary cause of migration is considered to be the deterioration of living conditions in the breeding range: a decrease in food quantity and availability, Changes in the intensity and duration of daylight, the appearance or disappearance of green foliage, snow cover, or ice on Water bodies, etc. The trigger for departure varies among species. For instance, swifts depart when daylight hours decrease, signaling an impending Temperature drop that affects the availability of flying insects—their sole food source.

Swallows depart later, as they are capable of catching insects not only in the air but also among the foliage of tree crowns, shrubs, and grass. Ducks begin to leave when water bodies freeze over, stripping them of access to the benthic food sources found in the silt.

Before migration, birds typically gather into flocks, which can range from a few dozen to tens of thousands of individuals. Regardless of size, a flock maintains a specific formation typical of each bird species. For example, cranes and geese fly in a V-formation or wedge; pelicans and lapwings form a wide, stretched-out chain; starlings move in a dense, closed mass; birds of prey fly seemingly independently, at great distances from one another, yet keeping each other in sight. Only a few species (such as cuckoos and robins) migrate entirely alone.

The timing of arrival, much like departure, is tied to environmental changes that provide birds with the necessary conditions for survival in spring—familiar food and shelter. Thus, nightingales and orioles, which forage in tree canopies, appear only when the leaves unfold; swallows arrive when flying insects are present in the air; and reed warblers appear once riverside vegetation has grown sufficiently. The return dates to breeding grounds vary significantly from year to year. This is especially pronounced in early-arriving species, when the weather remains highly unstable, causing arrival times to shift by up to 25 days. Late-arriving birds return to their breeding areas under more stable weather conditions, resulting in much smaller annual variations in arrival timing—up to 11 days. The duration of the migration journey also varies among species. For early-arriving species, the return period is protracted over 30–36 days, whereas for late arrivals, it typically spans 9–12 days.

The behavior of birds and their travel speed differ during autumn and spring Migrations. In autumn, birds fly slowly, often making prolonged stops in suitable habitats. In spring, migration is rapid, with stopovers being less frequent and of shorter duration. For instance, the bar-tailed godwit covers its 12,000 km migration route in 2-3 months during autumn, but in only 1-1.5 months in spring. The duration of continuous flight varies among bird species—from 0.5 hours in rooks to 35 hours or even more in plovers. Each bird species has its own migration speed. The hooded crow covers up to 50 km in an hour, while swifts can reach up to 170 km. Flight altitude for the overwhelming majority of species ranges between 450-470 m, though certain species can fly much higher, up to 8,850 m above sea level.

Spatial orientation and the choice of flight direction during migration have not yet found a conclusive scientific explanation. It is generally accepted that birds rely on visual cues during migration. Some navigate by terrestrial landmarks (such as rivers or cities), others by the sun and general sky illumination, and still others by the stars. What is particularly remarkable is that in some species (such as starlings), young individuals that have never migrated before are the first to fly south.

Quite often, the same species reacts differently to the onset of winter across different parts of its geographic range. For example, mallards are sedentary in England, but migratory in Finland. Changes in environmental conditions can also influence migratory behavior. For instance, ducklings hatched in Finland from eggs taken from non-migratory English parents migrated to wintering grounds in their very first year of life—mostly to the regions where their foster parents wintered. Conversely, migratory brent geese translocated to England using the same method became sedentary.

Environmental changes, particularly the expansion of large cities where certain birds like rooks and crows can find food even in winter, have led to these birds being commonly seen on the streets of cities in central regions during harsh winter weather. Some of them may indeed stay to overwinter, but the majority likely fly south, while individuals from more northern areas arrive to take their place in the central regions.

Review and Self-Assessment Questions:

1. How is the higher level of Organization in birds manifested compared to reptiles?

2. Which habitats are predominant among birds?

3. What general organizational traits characterize the class Aves (birds)?

4. What structural and physiological adaptations develop in birds in relation to flight?

5. What is the Internal Structure of a bird's egg?

6. What structural and lifestyle characteristics are typical of representatives of the superorders penguins, ostriches, and the order Neognathae?

7. What types of altricial and precocial chicks are distinguished in birds?

8. What is the Significance of Birds in nature and human life?

9. Into what groups are birds divided based on how they cope with unfavorable winter conditions?

10. What are the differences in bird behavior during autumn departure and spring arrival?

11. How do birds orient themselves in space?