<P> Animals form another important part of the house sparrow's diet, chiefly insects, of which beetles, caterpillars, dipteran flies, and aphids are especially important . Various noninsect arthropods are eaten, as are molluscs and crustaceans where available, earthworms, and even vertebrates such as lizards and frogs . Young house sparrows are fed mostly on insects until about 15 days after hatching . They are also given small quantities of seeds, spiders, and grit . In most places, grasshoppers and crickets are the most abundant foods of nestlings . True bugs, ants, sawflies, and beetles are also important, but house sparrows take advantage of whatever foods are abundant to feed their young . House sparrows have been observed stealing prey from other birds, including American robins . </P> <P> The house sparrow's flight is direct (not undulating) and flapping, averaging 45.5 km / h (28.3 mph) and about 15 wingbeats per second . On the ground, the house sparrow typically hops rather than walks . It can swim when pressed to do so by pursuit from predators . Captive birds have been recorded diving and swimming short distances under water . </P> <P> Most house sparrows do not move more than a few kilometres during their lifetimes . However, limited migration occurs in all regions . Some young birds disperse long distances, especially on coasts, and mountain birds move to lower elevations in winter . Two subspecies, P. d. bactrianus and P. d. parkini, are predominantly migratory . Unlike the birds in sedentary populations that migrate, birds of migratory subspecies prepare for migration by putting on weight . </P> <P> House sparrows can breed in the breeding season immediately following their hatching, and sometimes attempt to do so . Some birds breeding for the first time in tropical areas are only a few months old and still have juvenile plumage . Birds breeding for the first time are rarely successful in raising young, and reproductive success increases with age, as older birds breed earlier in the breeding season, and fledge more young . As the breeding season approaches, hormone releases trigger enormous increases in the size of the sexual organs and changes in day length lead males to start calling by nesting sites . The timing of mating and egg - laying varies geographically, and between specific locations and years because a sufficient supply of insects is needed for egg formation and feeding nestlings . </P>

Where do sparrows migrate to in the winter
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