Ruby-Throated Hummingbird

## Description

The ruby-throated hummingbird (Archilochus colubris ) is a species of hummingbird that generally spends the winter in Central America, Mexico, and Florida, and migrates to Canada and other parts of Eastern North America for the summer to breed. It is by far the most common hummingbird seen east of the Mississippi River in North America.

## Appearance

Ruby-throated hummingbirds are tiny colorful birds that breed in North America. Adults are metallic green above and grayish white below, with near-black wings. 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. 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. Males are smaller than females and have slightly shorter bills. Juvenile males resemble adult females, though usually with heavier throat markings. The bill of these birds is long, straight, and very slender. Their toes and feet are quite small.

## Distribution

Ruby-throated hummingbirds breed throughout most of the Eastern United States and south-central and southeastern Canada. These are migratory birds spending most of the winter in Florida, southern Mexico, and Central America, as far south as extreme western Panama, and the West Indies. Ruby-throated hummingbirds live in mixed deciduous and broadleaved forests, pine forests and forest edges, orchards, and gardens.

## Behavior

Ruby-throated hummingbirds are solitary and interact with each other only during the breeding season. Both males and females of any age are aggressive toward other hummingbirds. They may defend territories, such as a feeding territory, attacking and chasing other hummingbirds that enter. Ruby-throated hummingbirds feed frequently while active during the day. They feed from flowers using a long, extendable tongue and catch insects on the wing or glean them from flowers, leaves, bark, and spiders' webs. When temperatures drop, particularly on cold nights, they may conserve energy by entering hypothermic torpor. Ruby-throated hummingbirds communicate with rapid, squeaky chirps, which are used primarily for threats. For example, males may vocalize to warn another male that has entered his territory.

## Diet

Ruby-throated hummingbirds are herbivores (nectarivores). Their main food is nectar from flowers and flowering trees. They also feed on insects and occasionally sugar-rich tree sap taken from sapsucker wells.

## Reproduction

Ruby-throated hummingbirds are thought to be polygynous. However, polyandry (females have multiple mates) and polygynandry (both males and females have multiple mates) may also occur. The breeding season takes place in March-July. Males arrive at the breeding area in the spring and establish a territory before the females arrive. When the females return, males court females that enter their territory by performing courtship displays. They perform a "dive display" rising above the female. If the female perches, the male begins flying in very rapid horizontal arcs in front of her. 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. During the courtship displays, the male makes a rapid 'tik-tik tik-tik tik-tik' sound with his wings. The sound is produced both during the shuttle display, at each end of the side-to-side flight. Also, the sound is made during dive displays. The nest is usually constructed on a small, downward-sloping tree limb or in a shrub and is well camouflaged. It is composed of bud scales, with lichen on the exterior, bound with spider's silk, and lined with fibers such as plant down (often dandelion or thistle down) and animal hair. Old nests may be occupied for several seasons, but are repaired annually. As in all known hummingbird species, the female alone constructs the nest and cares for the eggs and young. She lays 1 to 3 white eggs and produces one or two broods each summer. Incubation lasts about 10 to 14 days. The female broods the chicks over a period of 12-14 days, by which point they are feathered and homeothermic. When the chicks are 18 to 22 days old, they leave the nest and make their first flight.

## Population

### Population threats

Ruby-throated hummingbirds are threatened by climate change that affects their migration patterns and by habitat loss due to agricultural growth and deforestation. They also suffer from predation by raptors and domestic cats and from collisions with windows.

### Population number

According to the University of Michigan (Museum of Zoology) resource, the total population size of the Ruby-throated hummingbird is 7,300,000 individuals. According to the All About Birds resource the total breeding population size of the species is 20 million breeding birds. Overall, currently, Ruby-throated hummingbirds are classified as Least Concern (LC) on the IUCN Red List and their numbers today are increasing.

### Ecological niche

While collecting nectar from flowers, Ruby-throated hummingbirds transfer the pollen and assist in plant pollination in their local ecosystem.

## Fun Facts

Of all hummingbirds in the United States, the Ruby-throated hummingbird has the largest breeding range.

During their spring migration, some populations of Ruby-throated hummingbirds fly from the Yucatan peninsula of Mexico across the Gulf of Mexico, arriving first in Florida and Louisiana. This feat is impressive, as an 800 km (500 mi), non-stop flight over water requires caloric energy that far exceeds an adult hummingbird's body weight of 3 g (0.11 oz). However, these tiny birds prepare for their Gulf crossing; they double their fat mass and then expend the entire calorie reserve from fat during the 20-hour non-stop crossing when food and water are unavailable.

Hummingbirds have one of the highest metabolic rates of any animal! Their heart rates are up to 1260 beats per minute, breathing rate is about 250 breaths per minute even at rest, and oxygen consumption is about 4 ml oxygen/g/hour at rest.

During the flight, hummingbird oxygen consumption per gram of muscle tissue is approximately 10 times higher than that seen for elite human athletes!

Hummingbirds have many skeletal and flight muscle adaptations that allow great agility in flight. 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. This adaptation allows the wing to rotate almost 180°, enabling the bird to fly not only forward but backward and to hover in mid-air; such flight capabilities are similar to insects and are unique among birds.

During hovering, hummingbird wings beat up to 80 times per second!

## References

https://animalia.bio/ruby-throated-hummingbird