EURASIAN TREECREEPER (Certhia familiaris) Grimpereau des bois and ……….SHORT-TOED TREECREEPER (Certhia brachydactyla) Grimpereau des jardins
Eurasian Treecreeper © Frank Jarvis
SUMMARY
Two species of treecreeper are found in Switzerland, and are very hard to identify until they sing. This article will help you to understand how to appreciate and identify these two members of a fascinating family.
I will treat these two species together on this page since, just like the Goldcrest and Firecrest, the two are very difficult to tell apart visually in the field. In fact, I think these two are harder to tell apart than the two small warblers. However, their song is your best friend!
© Frank Jarvis
Cryptic colours and forest gloom make viewing difficult © Arlette Berlie
Treecreepers are great little birds. Like miniature woodpeckers they have long stiff tails, and spend most of their time on the vertical surface of tree trunks. Not drilling of course, but poking and probing around with beaks like fine forceps, looking for insects (and spiders) in the crevices and cracks of the bark. Starting at a low to medium elevation on the tree, they work their way upwards (opposite direction to a Nuthatch) until they reach whatever they feel is the right height, at which point they will fly down to the next tree, and start all over again. A colloquial name from southern England is “tree mouse”, which aptly summarises its scurrying behaviour. They often go up spiralling around the trunk so just as you feel you are getting a good view of the bird it will disappear from view around the far side. They will also treat the larger branches in the same way. Measuring only about 12-13 cm, with a good part of that being taken by the long tail and curved beak, they are really small. They are superbly disguised with cryptic colouration which makes them hard to see and, to make matters worse, they like nothing better than getting in crevices and under the dry moss and lichen which may grow on the tree trunk. They are continuously active, hardly ever sitting still. So when the bird books tell you that the Eurasian Treecreeper has a slightly shorter beak, or that the Short-toed Treecreeper has slightly browner flanks, or looser feathers around its rear end giving it a different shape, then don’t despair if you can’t see this - most of us can’t! And certainly you are not ever going to get a great view of those short toes………..
Eurasian Treecreeper © Arlette Berlie
But back to the easier part, song:
EURASIAN TREECREEPER (Grimpereau des bois)
The Eurasian Treecreeper is, as its name suggests, found all across continental Europe to the Pacific Coast of China into Japan. It is found in the British Isles and it is the only Treecreeper to occur there. Switzerland is at the South-western edge of its range, and it occurs more frequently at higher altitudes between 1100-1700m, although it can go down to 500m where it is found sympatrically with the Short-toed (Knaus etal 2018).
By Jimfbleak at English Wikipedia, CC BY-SA 3.0, Green is Certhia familiaris.
But it is perhaps because of this preference for higher altitudes that I find the Eurasian Treecreeper less common than its close relative, even though it is distributed across most of the country. In Switzerland it prefers closed mixed forests (reflected in the French name) of older mature trees, which presumably offer more aged bark and better feeding.
Its song is a pleasant jingling sound. It starts with a brief trill at high frequency (around 7kHz) followed by 5-6 squeaky notes which slide up and down the scale and then suddenly drop with a flourish to about 3 kHz:
Here are two samples of song phrases repeated twice:
and here is a video which you can follow:
Eurasian Treecreeper song
SHORT-TOED TREECREEPER (Grimpereau des jardins)
By Jimfbleak at English Wikipedia, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=8277346
The Short-toed Treecreeper is a bird of more open country, and can be found in parks, gardens orchards, as well as deciduous forests, and most of the population is found below 900m. Like its higher altitude counterpart it prefers mature trees with deeply furrowed bark. This is a bird mainly of western Europe, and Switzerland is in the centre of its range. It does not occur in the British Isles nor any further north than Denmark, and extends east to parts of Turkey and occurs sporadically in North Africa.
Short-toed Treecreeper © Arlette Berlie
The very characteristic song consists of a series of rhythmic, bouncy notes in a rising scale from about 4.5 kHz to 7kHz, the second note is lower and longer than the first and so it givs the impression of being emphasised:
In my head, the rhythm goes “tip-teee-tweedle-eee-deee” (!), see if you agree in this longish sequence captured at dawn in an oak/beech forest:
Three extracted phrases of Short-toed Treecreeper
COMPARISON OF THE TWO:
To summarise it all, here are both birds compared - Short-toed first and Eurasian second:
Two phrases of Short-toed followed by two phrases of Eurasian Treecreeper
Which one is it ? An all-too-familiar view of a treecreeper © Arlette Berlie (it is Short-toed)
So there you have the songs of our two European Treecreepers and how these two species, almost identical in appearance, can be told apart in the field. In general, I find the song of the Short-toed more obvious when I am walking through the woods. It stands out and seems more persistent. This could be because of the simpler, more bouncy rhythm, whereas the song of the Eurasian is “thinner” and more complex. But a health warning: the songs are not strong, and are of high frequency (i.e. harder to hear by us older types!), they can mingle with the sounds of many other small birds who sing at similar frequencies - Goldcrest, Firecrest, various tit species, Hawfinch etc so it is not completely straightforward. Finally, be aware that there are studies which have found that each of these species can mimic the other on occasions and this is well enough studied for people to conclude the Eurasian is the better mimic (or maybe the simpler song of the Short-toed is easier to copy?). A study from Poland concluded that the main purpose of the song in both species was to protect their mate from other males, as opposed to attracting females or defending territory (Osiejuk and Kuczynski 2000), but how that fits with mimicry I cannot work out.
CALLS
Like all passerines, these two Treecreepers don’t only have a song - they have a series of calls for other communication purposes. But here, things get really tricky. Looking through all my archives, I find I have 4 different calls for the Eurasian and only 2 for Short-toed. Perhaps this indicates a more complex vocabulary for Eurasian - or perhaps it is a factor of my not very random sampling! It is very hard to know what to make of them. Each call is so very brief, often you can’t see what the bird is doing, and the high frequency makes it hard for human ears to detect differences (especially beyond the age of 25 !). However, I will give examples here of both the call and what that call looks like on a sonogram. The latter in case any of you are making your own sonograms you can make comparisons here:
Eurasian Treecreeper Call 1:
Eurasian Treecreeper Call 2:
(Yes, that was a Red Deer (Cerf) stag roaring in the background)
Eurasian Treecreeper Call 3:
Eurasian Treecreeper Call 4
You will notice that calls 3 and 4 are both slightly modulated which can be detected as a slight “rattling” of the sound. Younger people can probably detect that in the field, but I can still get it through headphones from the examples here.
Now on to Short-toed Treecreeper calls:
Short-toed Treecreeper Call 1
Short-toed Treecreeper Call 2
The Short-toed calls involve lower frequencies and so are more penetrating and less likely to be lost in the vegetation. I cannot explain what these calls signify, most likely contact between mated birds, or with their offspring, or even aggressive calls to warn off competitors. Note how that second call of the Short-toed seems very piercing; the lower note you hear is a Nuthatch which was in the same tree and close by, and the two seemed to be arguing over who had foraging rights. So that call may be indicating aggression towards another species who is probably a close competitor for food.
Studies of Eurasian Treecreeper from UK © Frank Jarvis
