0 the ruby-throated hummingbird (archilochus colubris) is a species of hummingbird that generally spends the winter in central america and migrates to eastern north america for the summer to breed .
1  it is by far the most common hummingbird seen east of the mississippi river in north america .
2 this hummingbird is from 7 to 9 cm (2.8 to 3.5 in) long and has an 8 to 11 cm (3.1 to 4.3 in) wingspan .
3  weight can range from 2 to 6 g (0.071 to 0.212 oz), with males averaging 3.4 g (0.12 oz) against the slightly larger female which averages 3.8 g (0.13 oz) .
4  adults are metallic green above and greyish white below , with near-black wings .
5  their bill , at up to 2 cm (0.79 in), is long , straight , and very slender .
6  as in all hummingbirds , the toes and feet of this species are quite small , with a middle toe of around 0.6 cm (0.24 in) and a tarsus of approximately 0.4 cm (0.16 in) .
7  the ruby-throated hummingbird can only fox-trot if it wants to move along a branch , though it can scratch its head and neck with its feet .
8 the species is sexually dimorphic .
9  the adult male has a gorget (throat patch) of iridescent ruby red bordered narrowly with velvety black on the upper margin and a forked black tail with a faint violet sheen .
10  the red iridescence is highly directional and appears dull black from many angles .
11  the female has a notched tail with outer feathers banded in green , black , and white and a white throat that may be plain or lightly marked with dusky streaks or stipples .
12  males are smaller than females and have slightly shorter bills .
13  juvenile males resemble adult females , though usually with heavier throat markings .
14  the plumage is molted once a year , beginning in late summer .
15 the breeding habitat is throughout most of eastern north america and the canadian prairies , in deciduous and pine forests and forest edges , orchards , and gardens .
16  the female builds a nest in a protected location in a shrub or a tree .
17  of all hummingbirds in the united states , this species has the largest breeding range .
18 the ruby-throated hummingbird is migratory , spending most of the winter in southern mexico and central america , as far south as extreme western panama , the west indies , and southern florida .
19  during migration , some birds embark on a nonstop 900 mile journey across the gulf of mexico and caribbean from panama to gulf coast .
20  the bird breeds throughout the eastern united states , east of the 100th meridian , and in southern canada , particularly ontario , in eastern and mixed deciduous and broadleaved forest .
21  in winter , it is seen mostly in mexico and southern florida .
22 ruby-throated hummingbirds are solitary .
23  adults of this species typically only come into contact for the purpose of mating , and both males and females of any age aggressively defend feeding locations within their territory .
24  the aggressiveness becomes most pronounced in late summer to early fall as they fatten up for migration .
25  this is important because , as part of their migration , they must fly across the gulf of mexico - a feat which long confounded scientists , as a 500-mile , non-stop flight over water would seemingly require a caloric energy that far exceeds an adult hummingbird's body weight of 3 grams .
26  however , researchers discovered the tiny birds can nearly double their body mass in preparation for their gulf crossing .
27  the additional mass , stored as fat , provides enough energy for the birds to achieve this amazing flight .
28 they feed frequently while active during the day and  when temperatures drop , particularly on cold nights , they may  conserve energy by entering hypothermic torpor .
29 due to their small size , they are vulnerable to insect-eating birds and animals .
30 hummingbirds have many skeletal and flight muscle adaptations which allow the bird great agility in flight .
31  muscles make up 25-30% of their body weight , and they have long , blade-like wings that , unlike the wings of other birds , connect to the body only from the shoulder joint .
32  this adaptation allows the wing to rotate almost 180, enabling the bird to fly not only forward but fly backwards , and to hover in front of flowers as it feeds on nectar and insects .
33 during hovering , ruby-throated hummingbird wings beat 55 times per second , 61 times per second when moving backwards , and up to 75 times per second when moving forward .
34  {citation needed|date=july 2011}nectar from flowers and flowering trees , as well as small insects and spiders , are its main food .
35  small arthropods are a more important part of adult hummingbirds' diet than has generally been recognized .
36  their diet may also occasionally include tree sap taken from sapsucker wells .
37  hummingbirds show a slight preference for red , tubular flowers as a nectar source .
38  the birds feed from flowers using a long extendendable tongue , and catch insects on the wing or glean them from flowers , leaves , bark , and even from spider's webs .
39 young birds are fed insects for protein since nectar is an insufficient source of protein for the growing birds .
40 ruby-throated hummingbirds are thought to be polygynous .
41  polyandry and polygynandry may also occur .
42  they do not form breeding pairs , and females provide all parental care .
43 males arrive at the breeding area in the spring , and establish a territory before the females arrive .
44  when the females return , males court females that enter their territory by performing courtship displays .
45  they perform a dive display rising 8  10 feet above and 5  6 feet to each side of the female .
46  if the female perches , the male begins flying in very rapid horizontal arcs less than 0.5 m in front of her .
47  the male's wings may beat up to 200 times per second during these displays (the normal speed is 55-75 beats per second) .
48 if the female is receptive to the male , she may give a call and assume a solicitous posture with her tail feathers cocked and her wings drooped .
49  ''preceding copulation , male and female face each other , alternately ascend about 10 feet and descend , eventually dropping to the ground and copulating .
50 the nest is constructed on a small , downward-sloping tree limb 1020 feet above the ground .
51  it is composed of bud scales , with lichen on the exterior , bound with spider's silk , and lined with plant down (often dandelion or thistle down) .
52  old nests may be occupied for several seasons , but are repaired annually .
53  the female constructs the nest , as the male has left by this point .
54 females lay two white eggs about 12.9 by 8.5 millimeters in size , and produce 2, or occasionally 3 broods .
55  they brood the chicks and feed them from 1 to 3 times every hour by regurgitation , usually while the female is hovering .
56  when they are 22 to 25 days old , the young leave the nest .
57 (0.5 x 0.3 in) .
58 the vocalizations of ruby-throated hummingbirds are rapid , squeaky chirps , and are used primarily for threats .
59  for example , males may vocalize to warn another male that has entered his territory .
