Life

Easily identified, for a warbler

May 23rd, 2016 5:00 PM

By Southern Star Team

The blackcap has a rich warbling song with varied notes and quite long phrases. (Photo: S Franks)

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The individual species in some groups of birds are frustratingly similar and they often have rather drab plumage with few distinguishing marks. ‘Little brown birds’ is a term used by birdwatchers to describe these small birds that are hard to identify.

Many of the warblers fit into this category – in fact the garden warbler is so featureless that some birdwatchers say that the best way to identify it is to look for a lack of distinguishing patterns in its plumage colouring.

However, there is one warbler that is easy enough to identify. As the name suggests, the blackcap has a black ‘cap’ on its head while the hen’s is of a more reddish hue. This was once a rarely seen bird around these parts but now there are more opportunities to see one year round.

 

Blackcap

As well as looking alike, warblers have similar life-styles. They all eat insects and most have melodious songs. The blackcap is grey-brown above and a paler ash brown below. Its coloured forehead and crown are glossy black in the male, while in the female this ‘cap’ is more a reddish brown. In autumn, young males can look slightly strange with a mixed cap of both black and brown feathers.

The blackcap has a rich warbling song with varied notes and quite long phrases. It starts to sing as early as March from its preferred perches in bushes or tree-tops, however, it usually uses the foliage to keep itself screened from sight. The blackcap’s glorious flute-like song is a joy to listen to.

The blackcap favours open woodland with thick undergrowth. Large gardens provide all their needs too, especially if they have some tall trees which act as songposts. They particularly favour evergreen trees.

 

Breeding

Most blackcaps arrive here as migrants from March onwards from their African and Mediterranean over-wintering grounds. They continue to fly in during April. Males arrive first and they quickly establish territories and start to sing. When the females arrive a week or two later, pairing can begin without delay.

Nest building and egg-laying take place in late April and early May. Blackcaps tend to build their nests in dense thickets, especially of briars. The nest is around 2 feet off the ground and so within easy reach of foxes, stoats and mink. Each year, about half of blackcap nests are raided by predators. The young are particularly vulnerable as it’s much easier to find a nest of calling chicks than one which an adult bird is silently incubating. 

This early breeding, and the rapid development of the young, allows some blackcap pairs to rear two broods in one year. Incubation of the blotched brown and white eggs only takes 12 days.

 

Confused migration

Some blackcaps overwinter in Ireland and Britain. It was once believed that these were summer migrants that simply remained in Ireland and didn’t make the return journey to their African/Mediterranean wintering grounds. 

However, it’s now been discovered that these are a different group of birds with an alternative migration pattern.

Instead of remaining in Ireland after the summer, these birds arrive in Ireland in autumn. They over-winter here and then make the return journey to their Central European breeding grounds in summer. Therefore these blackcaps are leaving Ireland around the same time as the ones from Africa are arriving here. 

This is the only bird to have two groups of different migration patterns to and from Ireland. And it is quite a recent development too, happening really in the last 50 years or so.   

It appears that a group of blackcaps from Central Europe somehow got ‘confused’. Instead of flying south-east to their wintering grounds, they flew south-west and ended up in Ireland. They over-wintered here, found it favourable and have continued this alternative migration pattern ever since then. This shorter migration uses a lot less energy and offers all sorts of other advantages too. Arriving in Central Europe before the African migrants do, our wintering birds get the prime nesting sites and are in much better condition for breeding.

Birds that occasionally go off course in this manner are called ‘vagrants’ but mostly they do correct their future migration route. We don’t know why this group didn’t ‘auto-correct’ its error over the following years. However, it’s very reassuring to see them having the ability to change their pattern so easily and within such a short time frame.

Many bird migration patterns date back to pre-history and the era of the last Ice Age. Now that our climate is changing at a more rapid pace, the fact that this species has been able to alter its migration so quickly provides hope that many more will be able to adapt as necessary too.

These opportunistic blackcaps have adapted to their new winter habitats successfully. The birds that overwinter in Ireland and Britain have learned to exploit the multiple bird feeders in our countries. They love peanuts and are very aggressive at the feeders, driving off other birds while they use them. 

 

The Irish nightingale

The Irish name for the blackcap is ‘caipín dubh’ literally means ‘little black cap’. It was also known as ‘Donnchadh an chaipín’ (Denis of the cap) and ‘Máirín an triúis’ (Maureen of the trousers). However, it was also known as the ‘Irish nightingale’. As the true nightingale is not found in Ireland, the musical blackcap and sedge warbler were both awarded this honour, presumably in honour of their wonderful singing abilities.

Blackcaps are considered ‘good eating’ and many of them are still killed for food as they pass through the Mediterranean area. They are caught with so-called ‘lime sticks’ – twigs covered in glue that are positioned in bushes and trees. The unfortunate blackcap alights and cannot escape from this cruel trap. They are also caught in fine nets. Both of these practices were also once used in Ireland but are now illegal.

Sharron’s wonderful photo of the male blackcap was taken in late March so he may one of our over-wintering Irish birds or one that had just arrived to breed. And we can look forward to seeing more of these lovely little birds at our bird feeders year round – even if they are little bullies at times!

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