Eurasian Blue Tit (London, UK)

As I mentioned in my previous post, writing is not necessarily my forte but I was very pleased to receive some great feedback from my recent article on the European robin. I have been planning on producing more of these informal blog posts but unfortunately, mainly due to the time pressures of a modern-day working life, I have not been able to do so. Photography has, and likely always will be for me, something that I engage in as an enjoyable pastime. Whilst it is a great way to escape from the hardships of full-time employment, finding sufficient time to engage in photography is always much more difficult than I would like it to be. It is also the reason that, when asked, I always describe myself as a truly amateur photographer. That being said, sharing my photographic images and writing informative posts such as this one hopefully provide people an insight into the natural world that surrounds us and, maybe, offers a brief escapism from the stresses that a modern-day life can pile upon us.


As I have mentioned before, I live in London, more specifically in the district of Chiswick. Similarly to the rest of London, Chiswick is a non-stop, full throttle type of area where people are constantly on the move and where there is plenty to see and do. Granted, Chiswick could readily be described as a ‘leafier area’ of London in comparison to others, with easy access to a number of green spaces and the River Thames flowing along its border. Still, London does not boast a reputation of being a wildlife haven but, as I have said before, the capital city is far more wild than one might first imagine.


Amongst some of the most common species found here in Chiswick are the songbirds or, to give them their proper name, the passerines. With around 6,500 different passerine species found worldwide, these birds make up over half of all the bird species in the world. The European robin is just one of these but another that you will have likely seen before is the Eurasian blue tit.

 

The Eurasian blue tit is a small member of the passerine family and one that can be seen all year round in gardens, parks and woodlands here in London. Their distinctive blue, yellow and white colouration make the blue tit one of the most recognisable garden visitors but, seeing one in your backyard may have more benefit than you might first think.


Eurasian Blue Tit (Canon EOS 1200D, Canon EF-S 55-250mm @ 166mm, f/5.6, 1/1600, ISO 3200)

Blue tits, like most smaller birds, have an extremely varied diet but the primary focus is on insects. One of their favourite meals are caterpillars and, it is actually possible to gauge how many caterpillars a blue tit has eaten, by their colouration. Caterpillars, specifically ones that are yellowy-green in colour, carry a high level of carotene pigment in their bodies, the same type of pigment that gives carrots and orange colour, and, when eaten by the blue tits, they give the bird the sulphur-yellow colour found on its chest. The more yellow a blue tit’s chest feathers are, the more caterpillars it has eaten, similar to the process of the pink colour of wild flamingos being due to astaxanthin (a carotenoid) that they absorb from their diet of brine shrimp.



Another of the blue tit's favourite insects to target are the aphids; in fact the Eurasian blue tit eats more aphids than any other UK bird species. Aphids, as you will be well aware if you are a keen gardener, are sap suckling insects which can cause irreparable damage to horticultural plants. Aphids themselves have a number of natural predators and play a vital role in the food chains of local ecosystems but, if you happen to take pride in your garden, attracting blue tits could provide the added benefit of a natural pesticide against both caterpillars and aphids alike.


How might someone attract blue tits to their garden? Firstly, as aforementioned, blue tits have a varied diet. Their primary source of food is insects, which are readily available during the breeding season and throughout the warmer summer months. However, throughout the winter this food source becomes far more scarce and the blue tits have to look for alternatives. This sees them visiting gardens more regularly, on the hunt for bird feeders stocked with suet balls, nuts and seeds. If you have ever seen a blue tit on a feeding station you no doubt will have seen their acrobatic skills for which they are also famed. These birds are incredibly agile, able to hang upside down or on the thinnest of tree branches with ease, making them incredibly well suited to collecting food from manmade feeders.

Eurasian Blue Tit (Canon EOS 1200D, Canon EF-S 55-250mm @ 235mm, f/5.6, 1/400, ISO 3200)

Another way to attract blue tits to your garden could be through the setting up of an artificial nest box. Eurasian blue tits are one of the most ready users of sheltered nest boxes within the UK and, whilst they will nest in any suitable hole within a tree, wall, or stump, blue tit pairs will return to the same hole year after year; meaning if you set up a box and it gets utilised, you could be seeing blue tit fledglings every year.


During the breeding season females are solely responsible for the incubation of eggs, of which an average clutch size consists of between 6-8. These eggs are usually laid during April or May and the male spends time collecting food to feed the female during this time whilst she undergoes the incubation. Once fledglings hatch they require a lot of food and it is not uncommon for the youngsters to be fed at a rate of one feed every ninety seconds. Given that their favourite food is caterpillars, it quickly becomes apparent that this species relies heavily on an abundance of its preferred food source to raise successful fledglings, an unfortunate fact that has become more and more troublesome in recent years.


Caterpillars rely on climate conditions to kickstart their emergence and, as has been the case in recent years, warming temperatures have seen this happening earlier and earlier in the calendar year. The past few years have seen temperatures rising here in spring; MetOffice data suggests that the mean temperature in February, measured just down the road in Kew Gardens, has risen by over half a degree in the past twenty years and, as you may remember, a few years back in 2019 the same weather station measured a new, all-time record UK February high of 21.2C.


This warming of the earlier months causes the caterpillars to emerge quicker year on year and, as a result, when the fledglings eventually do hatch the caterpillars are no longer around; often themselves unable to survive once the abnormal temperature highs reset to the usual, cooler averages or because they have already developed into their final stage; butterflies or moths. Eurasian blue tits have a first year survival rate of around 35%, which is fairly normal for a small passerine bird, but, given the lack of caterpillars for fledglings to eat, this is a number that has seen a decline in recent years.


Eurasian Blue Tit (Canon EOS 1200D, Canon EF-S 55-250mm @ 250mm, f/5.6, 1/800, ISO 3200)
 

For now though the Eurasian blue tit is not a species that is of any real conservation concern, the RSPB have had it listed as a Green Status species since 1996, but, like most wildlife on our planet, factors caused by continual climate change could eventually have a direct impact on this colourful acrobat. Currently, an ability to adapt to different food sources, such as nuts and seeds as well as the young buds of various trees, mean that this species is surviving well but the concern relates to the fact that not every UK passerine species, all of which adopt a similar breeding pattern, are able to adapt as quickly or as successfully. The result is a huge decline in the numbers of some passerine species; the tree sparrow, corn bunting and willow tit, a close relative of the blue tit, for example, have all seen UK populations decline by over 75% in the past 30 years. Hopefully, with a bit of help from artificial nest boxes and feeding stations, things will not be heading in the same direction for the much loved Eurasian blue tit.

Eurasian Blue Tit (Canon EOS 1200D, Canon EF-S 55-250mm @ 250mm, f/5.6, 1/500, ISO 3200)


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