WARBLERS rank among my favourite birds because of their inherent ability to tantalise and tease; a furtive blurry brown movement glimpsed in the scrub is followed by a snatch of flowing song – and then nothing. The elusive warbler has crept away like a mouse through the thick tangle of bramble stems and nettles, only for it to then remind one of its invisible presence by another short burst of music.
Over the next few weeks several different species of warbler will be arriving in Scotland to spend the spring and summer, and at the head of this influx is the chiffchaff, with the first birds often making their presence felt by the end of March or early April. This is a wonderful time of year, with the first wildflowers such as primroses and lesser celandines appearing and buds opening on trees. These signs of spring are complemented by the repetitive two-note call of the chiffchaff that lends the bird its name. In Germany it is known as the “zilpzalp” and in Holland the “tjiftjaf”.
I barely recall hearing chiffchaffs in Scotland in the 1970s and early 1980s, but in recent decades they have really expanded their range and can be found in many parts of the country.
Small with greenish-yellow plumage, the chiffchaff is rather unremarkable in appearance and looks almost identical to its close cousin the willow warbler, which arrives in Scotland slightly later. The willow warbler has a truly fabulous song, rising in pitch, then descending in a sweet cascade of notes.
But when it comes to song with sheer depth and power, then the blackcap is a real show-stealer. These warblers arrive here from mid-April onwards and they soon make their presence known with an astonishingly loud burst of melody, which is so striking that old English names for the blackcap include “mock nightingale” and “northern nightingale”. Interestingly, while our summer visiting blackcaps head south to winter in the Mediterranean region, they are replaced by much smaller numbers of blackcaps from central Europe that visit the UK (including Scotland). Warblers are essentially insect feeders, but these wintering blackcaps can survive by eating berries, foraging for invertebrates in nooks and crannies, and visiting bird tables for food.
The garden warbler, which occurs in scrubby areas and along woodland edges, has a very similar song to the blackcap. Despite its rich musical repertoire, I find it one of our most challenging warblers to see as it is always very secretive, rarely being in the open long enough for one to get a good view.
Much more obvious is the whitethroat, a delightful little warbler with a scratchy song that the male often delivers in an intermittent flying courtship display. The strangest call, however, belongs to the grasshopper warbler, which sounds a bit like fishing line being drawn out from a reel.
It is a fickle bird and in some years several can be heard along the river valley near where I live, but in others it is totally absent.
Our warblers are engaging birds that provide good indicators of the state of our environment. The reed warbler, for example, has colonised southern Scotland only in very recent times as part of a northwards expansion, which could be a consequence of climate change. Others, such as the wood warbler, are declining, possibly due to losses in the specific type of woodland it requires for breeding.
Warblers love untrimmed hedges, bramble tangles and nettle patches – all habitats that are increasingly vulnerable. The drainage of wetlands is an ever-present menace to our populations of grasshopper and sedge warblers. And because warblers are migratory, droughts and other environmental fluxes in their sub-Saharan wintering grounds pose real threats.
It is for all these reasons that ornithologists take such a keen interest in monitoring changes in our warbler populations. But while there is no doubting warblers’ important role as environmental barometers, it is their extraordinary singing that really makes them so special. For me, they are the very heart and soul of our countryside during spring and early summer.