Ever heard of Little Brown Jobs? Or LBJs for short! This is a birder’s term for small nondescript birds that at first glance look like all the others. Chiffchaffs and willow warblers fit this description well. Brown and just larger than wrens, they look so alike that until the late 1700s they were thought to be the same species: ‘willow wrens’, named after willows in which they spend much of their time. So what hope for us who want to identify them? Their voices are the clue…
Chiffchaffs began arriving in Burwell in March, from North Africa where they went for winter sun. Males fly in first to grab the best territories for nesting. We know they are chiffchaffs by their loud, quite harsh, two note call, by which they are named: Chiff Chaff, Chiff Chaff. To spot one, listen out for this call, follow it and look for a small bird, just bigger than a wren, darting about a tree, picking up tiny insects off the bark and leaves. You can listen to chiffchaff song here: https://www.rspb.org.uk/birds-and-wildlife/wildlife-guides/bird-a-z/chiffchaff/
Willow warblers started arriving in Burwell at the beginning of this month, just after we went into lockdown. They have a longer journey here than chiffchaffs, coming from south of the Sahara. Willow warblers too can be seen flitting in trees, especially willows, feeding on tiny insects. Their call is a beautiful, liquid series of notes, that descend down the scale, tailing off into quiet. Neil Larner taught me to recognise their song twenty years ago. He described it as water going down a fountain, a description that really works for me. You can listen to willow warbler song here: https://www.rspb.org.uk/birds-and-wildlife/wildlife-guides/bird-a-z/willow-warbler/
I find having an image for a bird’s song helps me to remember and recognise it. I’d love to know if you have a way of describing willow warblers’ song.
Gilbert White, author of ‘The natural history of Selborne’ published in 1789, closely observed and kept a diary of the birds, flowers, and butterflies he saw. He worked out that Chiffs and Willow Warblers were separate species:
No two birds can differ more in their notes, for the one has a joyous, easy, laughing note, the other a harsh loud chirp… the songster [willow warbler] is one-fifth heavier than the chirper [chiffchaff]. The chirper, being the first summer bird of passage that is heard, begins his two notes in the middle of March, and continues them through the spring and summer…Taken from ‘A history of Ornithology’ by Peter Bircham.
There are subtle colour differences, chiffchaffs have darker legs, young willow warblers are yellower… but when looking in a bush at one of them, listening to it sing is the clincher.
Both species make a funnel shaped nest on or near to the ground, out of grasses and reed leaves. These nests are incredibly difficult to spot. Be aware of this if you have dogs, a quick run through a patch of longer grass adjacent to scrub or reeds can upturn a nest in a trice, and the birds’ long flight here and hours of concentrated effort are in vain.
I ring birds at Wicken Fen – we catch birds under special licence to put a light metal ring on their ankle, with a unique number, and take measurements such as weight and wing length of each bird. We do this to understand birds better, which in turn assists in taking effective conservation measures for species that are declining. Ringing is also awe inspiring. Last year I caught a willow warbler at Wicken Fen. The bird already had a ring. When I read the number, I realised I had ringed that very bird the year before, in exactly the same part of the Fen. In between, this bird, which weighs less than the weight of two 20p coins (c. 9g), had flown 9,000 miles to West Africa and back. Without a sat-nav!
When I taught Nathalie, my elder daughter to recognise a chiffchaff, we had a competition to see who would hear one first. When one of us heard a ‘Chiff – Chaff’ we would quickly give the other a (gentle) punch on the arm. The advantage of staying silent is that it gives the other person a chance to hear. We continue this game as a bit of fun. Have a go and see who wins…