Electric blue in the fast lane

One result of the shortage of rain this summer has been the reduction in flow of the tributaries of the main rivers, in our case the Aude. We live in a water mill perched above the Brezilhou stream, and not for the first time see why the original mill, dating from about nine hundred years ago, was built here. Upstream all the flow has gone underground, but whilst the waterfall that feeds the mill pond has slowed, it would have still supplied enough to keep the ponderous wheels turning. 

Kingfisher dive

 

Somewhere upstream a pair of Kingfishers nest every year. I have not found this year's nest, the older ones of previous years have been washed away in the floods that will eventually come. This year we see a kingfisher nearly every day, there is often a spark of electric blue and the piercing cry as these brightest of birds make the kilometre journey down to the main river to hunt for their meals – and sometimes they stop at the millpond and try their luck here. 

 

Searching the millpond

So, a few days ago, I was delighted to see three fly away simultaneously from various perches round the pond. They would have been from the same family, a kingfisher – both males and females - will hold and defend a length of water sufficient for their needs, and they may merge the territories together in February if they choose to breed together. If successful, the six to seven eggs laid in March or early April will hatch at the end of the nest tunnel built in a sandy bank where a chamber is excavated, they fledge after about twenty-five days, are fed for a further four and then the parent couple will drive them away - so quickly that some of them have not yet learnt to fish for themselves, and thus die from starvation. the adults then go on to have two even three clutches in the same year. 

Researchers have seen that there is a wonderful feeding arrangement in the nesting chamber, where the chicks rotate in a roundabout formation waiting for the next visit from a parent with its beak-full of fish. If this works each chick gets its turn, and then they all shuffle around! Whether it is quite so perfect as this another question, but ideally this is how it works.

A well used nest in the bank upstream

Kingfisher numbers fluctuate wildly from year to year. A hard winter will decimate numbers, but, with breeding success, they can bounce back. Most importantly, by mid-September each bird will have had to establish its own winter territory, to provide enough food for the hard months ahead. Only a quarter of the adults survive from one season to the next, and very few breed for more than one season.

 

Juveniles with white tips on the beak; A. Henderson

All this shows that this is a species that live in the fast lane of life. Each adult has eat at least its body weight in small fish, or shrimps and tadpoles every day, and in the nest every gaping mouth will eat six or seven minnows a day. A busy life, and often over very quickly. Note the intense stare in the following photo; having fixed a prey and judged its depth, it will dive, opening its beak and shutting the protective eyelid, in effect diving blind – but it works!

 

Needless to say the most striking thing about kingfishers that we, humans, notice, is their brilliant colours. So the question this brings is why evolution has developed something so dazzlingly extraordinary. Interestingly, all my photos show only male kingfishers, the females have a red base to the lower beak – they ‘wear lipstick’, the joke goes. However, my friend Adrian has one photo that there is a hint of red at the base of the beak, so a female, but probably a juvenile.

A female, with red on the lower beak

 

Ever since the time of Darwin it has been known, and proven by modern research, that it is very often the females that make sexual selection of mates on criteria that we humans are just to slow and to see, unless we use photography and scientifically study the colours (and sounds and movements). Many birds see also in the UV spectrum, and so a colour will have a range of subtlety to them beyond our abilities. All these clues can give a choosy female information as to the health and vigour of a male bird, and she will choose to mate with him – or not – on what she is able to detect, sometimes in a flash, as he patrols a neighbouring territory. Thus, a brighter blue and vibrant  orange breast may lead her to choose mate and pass on those characteristics to their progeny, and thus evolution works its magic.

 

A fine looking male

Another example of the speed of existence in the avian world is shown by a bird that none of us will see, unless we travel to  America; the Broad-tailed Hummingbird. It has a display flight that is “one of the world’s coolest, weirdest courtship displays” according to Mary Casswell Stoddard who has studied them in Colorado. The details are complex and wonderful, but suffice it to know that the male dives down on a perched female at a speed of 385 times its body length per second, relatively nearly twice the speed of a diving  peregrine, or the space shuttle during atmospheric re-entry (207 body lengths a second); at full speed at the bottom of his dive his” gorget flashes a vivid, sexy magenta, then its iridescence nature causes a change – in a mere 120 milliseconds –from bright red to dark green, as he passes over”. The amazing thing is that the female can see these precise details, and makes a mate choice as a result.