The ultimate nest architects

The nesting season is well underway for a host of avian species as we progress ever further into spring. One bird in particular that I’ve enjoyed spending time watching recently as they’ve busied about constructing their nests is the superb Long-tailed Tit.

Looking like a shuttlecock with wings, these excitable little 9-gram birds spend the winter foraging in tightly-knit family parties of between 8 and 20 members, associating with a mix of crests, tits and warblers in classic woodland feeding parties. Suffering high mortality in harsh overwinter conditions, these family groups will cluster together on cold nights in a communal roost, which greatly reduces their heat loss and thus conserves precious energy.  Come early spring (as early as January in some places) the mature breeding pairs will often peel off these flocks and head to their territories to set about the task of raising a family.

320A5886-2
a long-tailed tit gathering some lichen – one of some 6000 pieces it may collect over the course of a couple of weeks to create its work of art

Long-tailed Tits are renowned for their nests – and with good reason too! They take the art of nest building to a level unsurpassed by many common British songbirds. The domed structure often resides in a tangle of scrub, such as bramble or hawthorn, or perhaps in the fork of a young tree obscured by fresh leafy growth. The initial building process can take three weeks to complete, and yet later in the spring can be achieved in just a few days – mostly as a result of milder ambient conditions, and so a reduced need to insulate the nest so effectively.

320A7102
they’re just the cutest really, aren’t they?

The nest itself is a true work of art: the basis of the structure is an amalgamation of moss delicately interwoven with spider’s silk and hair. These ingredients, with the addition of feathers, can surpass 6000 fragments in a single nest! Hundreds of miniature bits of foliose lichen (particularly of the species Parmotrema perlatum) are stripped from nearby branches and stuck to the outside as means of camouflage, whilst other fragments and hair sprigs of moss are used almost like velcro to hold the whole ball together. The whole mis-mash of ingredients are essentially piled together with some dexterity, and the cup within is created by the birds periodically sitting inside and simply shuffling around to mould the centre into the correct size and shape. Eventually the sides are built to an appropriate height, and one edge is teased over to create a domed roof, before being affixed with more lichen and spider’s silk.

20170327_145912

20170327_145912-2
A couple of shot of one of the long-tailed tit nests I’ve been watching daily as they’ve been constructed. The outer layer is almost entirely composed of small pieces of foliose lichen, which have small, stiff hairs on the underside to act like velcro

Once the nest walls have been sufficiently plastered with lichen, and the oval dome secured in place, the next stage of construction is (as with any house), populating its interior. And this is where Long-tailed Tits really do go the extra mile: over 2600 feathers are used to adorn the cup lining of their nests, which must provide an enormously comfortable pad on which to incubate their clutch of eight eggs. Feathers account for roughly 40% of the total mass of Long-tailed Tit’s nests, although this varies through the season. Studies have shown that pairs will gradually decrease the feather lining of their nest as the spring wears on, countering increasing ambient temperatures. Essentially, this means they are able to gauge the temperature inside their nest, and adjust the nest insulation meticulously to ensure that eggs and chicks are kept at the optimum temperature throughout their upbringing!

320A7052-2

320A7038
Gathering the essential insulation material that makes up 40% of the nest’s mass

These long-tailed tit nests were brought out for a practical last term within our Biology of Birds module, and it was awesome to get a really close look at the intricate workings that had gone into their construction! Andy McGowan, one of the department’s lecturers and active researchers at the University of Exeter, has published a couple of really interesting papers on Long-tailed Tits. Check this one out!

The story doesn’t end there – these ingenious little birds have another trick up their sleeve. Once a nest has been completed to satisfaction, the eggs are laid and the incubation stint lasts for just over two weeks. Unfortunately, long-tailed tits have incredibly low success rates of just 17%, suffering largely from high predation rates. To maximise their chances, some breeding pairs may recruit an extra pair of hands, as it were. Helpers, perhaps chicks from previous years, or even failed breeders from the same spring, will bring food and contribute to protecting and raising a pair’s offspring. Why on earth would they bother to help, you may wonder? Remember how the family parties gather together in the winter to combat those cold night-time temperatures? Well, it is thought that by increasing the survival chances of a brood, helpers indirectly increase their own survival chances by ensuring that there will be enough birds to huddle together during the winter. The communal roosts will often take the form of a stringent hierarchy, with the dominant breeding pair in the very centre (i.e. taking the warmest spot), and then progressively younger birds positioned towards the periphery. A pretty devious tactic if you ask me!

320A6591
The long-tailed end of a long-tailed tit! Apparently the Swiss Gemran name for this bird is “Pfannestieli”, which translates roughly to ‘pan handle’

So these are truly remarkable little birds, and it’s been fantastic to watch as many as three different pairs around the Falmouth area constructing nests in dense bramble bushes. I’ve watched as pairs whizz back and forth – first with lichen and moss and hair, then laterally with beak-fulls of downy feathers as the nest nears completion. These visits are always accompanied by the trilling and chirruping ‘tsurp‘ and other higher-pitched calls. I’ve taken a lot of images of the various pairs whilst observing their behaviour, so here is a small selection of my favourites…

320A6478

So next time you’re out and you hear that unmistakable chirruping call, spend a bit of time watching and you may be treated to finding one of these amazing pieces of architectural design yourself!

Advertisements

2 thoughts on “The ultimate nest architects

  1. Reblogged this on opwildlife and commented:
    I’ve seen long tailed tits around Orchard Park on just a couple of occasions. I’d love to see them again. I’ve had several visits from its cousin the great tit collecting llama wool, hung out for the birds, to use as nesting material. If you can’t get your hands on that, put your own hair (after washing and before any styling products) out, or brush the dog outside.

    Like

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s