the downy woodpecker (picoides pubescens) is a species of woodpecker , the smallest in north america .
adult downy woodpeckers are the smallest of north america's woodpeckers but there are many smaller species elsewhere , especially the piculets .
the total length of the species ranges from 14 to 18 cm (5.5 to 7.1 in) and the wingspan from 25 to 31 cm (9.8 to 12.2 in) .
body mass ranges from 20 to 33 g (0.71 to 1.16 oz) .
standard measurements are as follows: the wing chord is 8.510 cm (3.33.9 in), the tail is 46 cm (1.62.4 in), the bill is 11.8 cm (0.390.71 in) and the tarsus is 1.11.7 cm (0.430.67 in) .
the downy woodpecker is mainly black on the upperparts and wings , with a white back , throat and belly and white spotting on the wings .
there is a white bar above the eye and one below .
they have a black tail with white outer feathers barred with black .
adult males have a red patch on the back of the head whereas juvenile birds display a red cap .
the downy woodpecker is virtually identical in plumage pattern to the larger hairy woodpecker , but it can be distinguished from the hairy by the presence of black spots on its white tail feathers and the length of its bill .
the downy woodpecker's bill is shorter than its head , whereas the hairy woodpecker's bill is approximately equal to head length .
the downy woodpecker gives a number of vocalizations , including a short pik call .
like other woodpeckers , it also produces a drumming sound with its beak as it pecks into trees .
compared to other north american species its drums are slow .
despite their close resemblance , downy and hairy woodpeckers are not very closely related , and they are likely to be separated in different genera; the outward similarity is a spectacular example of convergent evolution .
why they evolved this way cannot be explained with confidence; it may be relevant that the species exploit rather different-sized foodstuffs and do not compete very much ecologically .
downy woodpeckers are native to forested areas , mainly deciduous , of north america .
their range consists of most of the united states and canada , except for the deserts of the southwest and the tundra of the north .
mostly permanent residents , northern birds may migrate further south; birds in mountainous areas may move to lower elevations .
downy woodpeckers nest in a tree cavity excavated by the nesting pair in a dead tree or limb .
in the winter , they roost in tree cavities .
downy woodpeckers forage on trees , picking the bark surface in summer and digging deeper in winter .
they mainly eat insects , also seeds and berries .
in winter , especially , downy woodpeckers can often be found in suburban backyards with trees and will feed on suet at birdfeeders .
