Hummingbird

Anna's hummingbird

Anna’s Hummingbirds (Calypte anna), no more than 4 inches in size, are common in Western Californian yards, parks, residential streets, eucalyptus groves, riverside woods, savannahs, and coastal scrub. They readily come to hummingbird feeders and flowering plants, including cultivated species in gardens.

Anna’s Hummingbirds are mostly green and grey, without any rufous or orange marks on the body. The male's head and throat are covered in iridescent reddish-pink feathers that can look dull brown or grey without direct sunlight. Females are plain green above, and dingy grey below, often with red spots on the throat. They subsist mostly on nectar and insects. Takes nectar from flowers, and will feed on tiny insects as well. Will also feed on sugar-water mixtures in hummingbird feeders.

Anna’s Hummingbirds are a blur of motion as they hover before flowers, looking for nectar and insects. If you listen carefully, you can hear the male's scratchy metallic song and look for him perched above head level in trees and shrubs.

Anna's Hummingbird was named in honour of Anna Masséna, the Duchess of Rivoli and wife of French ornithologist François Victor Masséna, Duke of Rivoli. The bird was named as a tribute to a European noblewoman by the French naturalist René Primevère Lesson in 1829, to honour her social status and her family's interest in natural history and ornithology.

Fascinating Facts on Hummingbirds

• These smallest of warm-blooded animals also have the fastest wingbeats and heartbeat of any bird, and they are the only birds that can fly backwards and straight up and down. 
• If there were a bird version of competitive eating, they’d surely nab a prize for being able to consume half their body weight in food every day. And they have the amazing ability to lower their body temperature on a nightly basis to save energy
• Last but not least, hummingbirds really are the champions of the bird world when it comes to attention-grabbing iridescent colours. 

The science behind iridescence in birds

Sunlight reaches the Earth as white light comprising a range of different light waves containing all of the visible colours of the spectrum for humans, and some invisible ones.

When we see a colourful bird like a bright red Northern Cardinal, we are seeing waves of light reflected back to us via pigment molecules inside its feathers. Pigments absorb some wavelengths of light and reflect others.

So the Northern Cardinal’s red pigments absorb all visible light wavelengths except red, which is reflected to our eye and becomes the colour we see.  

Hummingbird feathers create their magical effects by capturing, bending, and reflecting beams of sunlight using almost inconceivably tiny structures built into their feathers. Hummingbirds have a plethora of thin, flat barbules at the outermost parts of their feathers, which are perfect for creating shiny, reflective iridescence.

Unlike other birds, the barbules in hummingbirds are flattened and contain layer after layer of flattened, air-filled discs called melanosomes, stacked on top of each other like pancakes. There can be as many as 15 of these melanosome layers per barbule, and this is where the magic happens. As light hits the top edge of the barbule, it refracts through a thin layer of transparent keratin and hits the top layer of melanosomes. Some light gets reflected, and some passes through, refracting (or bending) as it goes. The same thing happens as the passed-through light reaches the next layer, and the next, and the next: some light is reflected back, while some of it passes through. So when waves from these multifaceted reflections line up, it creates the brilliant colours we see.

The precise colour we (and hummingbirds) see depends on the finer points of the arrangement of the melanosomes. More densely packed, thinner layers generally result in colours on the blue and violet end of the spectrum. Thicker layers tend to create reds and oranges. 

Because there can be a dozen or more of these melanosome layers, the interplay between the sunlight and the nanostructures inside hummingbird feathers is extremely complex.

The diversity of colours found in hummingbirds exceeds that of all other bird species combined. The hummingbird spectrum includes saturated blues, blue-greens, and deep violets, as well as a host of ultraviolet and ultraviolet-blended colours that look one way to humans, but different to hummingbirds, such as UV-plus-green. 

According to ornithologists, the evolutionary conditions for a lot of hummingbirds are right for the kind of competition that produces a profusion of "fancy males", which gives an edge in terms of interaction, sexual display, or ecological competition. This theory of sexual selection, which dates back to Charles Darwin, posits that the eye-catching plumage of many male birds is a result of millions of years of brighter individuals competing more successfully for mates; evolution then favoured traits for brightness that were passed down and amplified over time.

Source: https://www.allaboutbirds.org/news/what-is-the-essence-of-iridescence-ask-a-hummingbird/