Tree sparrow, German sparrow
The Eurasian tree sparrow (Passer montanus) is asmall passerine bird that breeds over most of temperate Eurasia and Southeast Asia, where it is known as the Tree sparrow. It has been introduced elsewhere including the United States, where it is known as the Eurasian tree sparrow or German sparrow to differentiate it from the native unrelated American tree sparrow.
The adult's crown and nape are rich chestnut, and there is a kidney-shaped black ear patch on each pure white cheek; the chin, throat, and the area between the bill and throat are black. The upperparts are light brown, streaked with black, and the brown wings have two distinct narrow white bars. The legs are pale brown, and the bill is lead-blue in summer, becoming almost black in winter. This sparrow is distinctive even within its genus in that it has no plumage differences between the sexes; the juvenile also resembles the adult, although the colors tend to be duller. Its contrasting face pattern makes this species easily identifiable in all plumages; the smaller size and brown, not grey, crown are additional differences from the male house sparrow. Adult and juvenile Eurasian tree sparrows undergo a slow complete molt in the autumn and show an increase in body mass despite a reduction in stored fat. The change in mass is due to an increase in blood volume to support active feather growth and generally higher water content in the body.
Eurasian tree sparrows breed over most of temperate Eurasia and Southeast Asia. They are sedentary over most of their extensive range, but northernmost breeding populations migrate south for the winter, and small numbers leave southern Europe for North Africa and the Middle East. In Europe, these sparrows are frequently found on coasts with cliffs, in empty buildings, in pollarded willows along slow water courses, or in open countryside with small isolated patches of woodland. They prefer to nest near wetland habitats and avoid breeding on intensively managed mixed farmland. In eastern Asia, they are frequent visitors to urban areas while in southern and central Asia, these birds may be found around towns and villages.
Eurasian tree sparrows are diurnal and social birds. They feed and roost in flocks and even may even nest in loose colonies. Sparrows use several feeding strategies; they can feed as "producers", searching for food directly, or "scroungers", just joining other flock members who have already discovered food. Eurasian tree sparrows don't have a true song, but their vocalizations include an excited series of 'tschip' calls given by unpaired or courting males. Other monosyllabic chirps are used in social contacts, and the flight call is a harsh 'teck'.
Eurasian tree sparrows are herbivores (granivores) and carnivores (insectivores). They predominantly eat seeds and grain including chickweeds, goosefoot, and spilled grain. They may also visit feeding stations, especially for peanuts. Eurasian tree sparrows will also feed on invertebrates, especially during the breeding season when the young are fed mainly on animal food; these include insects, woodlice, millipedes, centipedes, spiders, and harvestmen.
Eurasian tree sparrows are monogamous and form long-lasting pair bonds. They breed in spring and then again in autumn. The male calls from near the nest site to proclaim ownership and attract a mate. He may also carry nest material into the nest hole. Pairs may breed in isolation or in loose colonies, and will readily use nest boxes. The birds typically build their nest in a cavity in an old tree or rock face. The untidy nest is composed of hay, grass, wool, or other material and lined with feathers, which improve thermal insulation. A complete nest consists of three layers; base, lining, and dome. The typical clutch is 5 or 6 eggs, white to pale grey, and heavily marked with spots, small blotches, or speckling. The eggs are incubated by both parents for 12-13 days. The chicks hatch altricial (helpless) and naked and fledge in 15-18 days. They reach reproductive maturity and start to breed within a year from hatching.
The Eurasian tree sparrow is not endangered globally, but there have been large declines in western European populations, in part due to changes in farming practices involving increased use of herbicides and loss of winter stubble fields. The change from mixed to specialized farming and the increased use of insecticides has reduced the amount of insect food available for nestlings.
According to the IUCN Red List, the total population size of the Eurasian tree sparrow is 190,000,000-309,999,999 mature individuals. In Europe, the breeding population consists of 24,000,000-38,200,000 pairs, which equates to 47,900,000-76,400,000 mature individuals. Currently, this species is classified as Least Concern (LC) on the IUCN Red List, and its numbers today are decreasing.
