Wildlife: The Kingfisher
PUBLISHED: 10:07 17 March 2014 | UPDATED: 10:14 17 March 2014
If you're stealthy and fortunate a waterside walk might be enlivened by the sight of an electric blue streak… Paul Hobson investigates
Over the last three winters we have experienced some very severe weather with really oddly timed cold snaps. When the snow does fall it often creates (in our minds at least) a fairytale landscape. As the days progress and the snow refuses to go away our initial wonder fades and turns to frustration while the cold penetrates our homes. We worry about energy bills and can’t believe how a little snow can bring one of the most technologically advanced societies to its knees as infrastructure creaks to the tune of winter wonderland.
So it is with us, but what about small delicate birds that depend on open water to feed? Once this is locked away beneath snow and ice, the larder is firmly closed, the food is effectively gone. Couple this calamity with the energy-sapping cold at night and there’s little wonder that this can rapidly become a disaster.
Kingfishers are known to suffer badly in cold winters. In 1963, a particularly bad winter, their numbers plummeted by 85 per cent. The last three winters have been very icy with prolonged cold spells. This is usually bad news for kingfishers but surveys indicate that our local kingfishers didn’t suffer as badly as initial fears suggested.
Oddly, kingfishers are not naturally the most successful species at surviving from one year to the next regardless of the weather. They are very territorial birds with both sexes fighting hard (even to the death) to protect their river, canal or lakeside beat. This is usually between 1km and 2km long and should provide enough fish for them to survive the winter. Kingfishers are not big birds but because they have a high metabolic rate and are small, they need to eat at least 60 per cent of their own body weight per day. A single bird needs 5,000+ fish over a typical summer. In winter the males and females hold separate but often adjoining territories which they marry up in early spring in readiness for breeding.
Kingfishers create their own tunnel in the waterside bank by drilling into it with their beaks and tiny feet. You can often spot a new burrow by the accumulation of fresh earth just below it – as long as it’s in a place where it won’t be washed away.
Once the burrow is complete the female lays five, six or seven eggs which the pair takes turns incubating. Eggs take about three weeks to hatch and the voracious young spend another three weeks in the nest. The adults have to fish really hard to satisfy the huge appetite of their youngsters. It is now that the intimate knowledge of their own territory comes into play as they are familiar with every spot where the fishing is good.
Unfortunately streams and rivers (canals and lakes less so), are very dynamic and heavy rain is not only a threat to eggs and young in nests but also changes the distribution of slow-flowing areas and pools in the river system where the small fish accumulate. Kingfishers are well adapted behaviourally to this and will explore every new situation as it is created to learn quickly where the fishing is best.
Once the first brood is fledged many kingfishers will try for a second and even third later in the summer. Sometimes they are so keen to get on with this that they drive the first youngsters from the territory before they can fish successfully. Due to their inexperience only 50 per cent of fledged kingfishers survive their first two weeks. The majority drown as they get waterlogged or starve as they can’t find a good fishy stretch of water to feed in.
In fact only a quarter of the youngsters survive to their first spring, so it does seem that the odds are stacked against them. Add to this the fact that only 25 per cent of adults survive to the next year and it seems even more incredible that after a harsh winter the kingfisher has any chance of bouncing back. However, they do, and have done for thousands of years.
Of course, this was all before we came onto the scene but we have learnt the error of many of our ways. Our rivers, canals and lakes in Derbyshire are cleaner than ever, they teem with fish and the vast majority, including the Derwent, Noe, Dove, Erewash and even the once famously dead Rother, are havens for our electric blue fisher.
We have even started to give them a helping hand with breeding. Kingfisher banks are created in many watery worlds so that the birds can find a safe haven to dig that all important tunnel.
There are so many facts that make the kingfisher a marvel to witness but one that is not commonly known is one that I find amazing. When a kingfisher perches and watches for fish, it has to contend with refraction, or how the light bends when it leaves the water and enters the air. If the kingfisher dived where it thinks the fish is, it would miss because of refraction. To get around this, the kingfisher has evolved the most amazing eyes. We have one area where most of the light falls onto the back of our eyes, giving us the clearest sight, but the kingfisher, unike other birds, has two. One area is for seeing in the air and the other for underwater. It switches between the two as it dives. I always thought that when a kingfisher dived it shut its eyes and relied on the memory of where the fish was, but it keeps its eyes open and uses them all the time to target the fish. Simply stunning!
So although bad winters are a severe problem for the halcyon bird, kingfishers are well designed to survive in their world and will always bounce back, even when statistics seem stacked against them.