COMMON REDSTART (Phoenicurus phoenicurus) - Rougequeue à front blanc
© Arlette Berlie
Summary
A very attractive little bird, not that common, favouring open woodlands, parks and gardens. It has a short penetrating song phrase that starts with a few rattling notes, each individual designing it’s own, followed by rapid-fire accurate mimicry of other species.
The white forehead, black face and orange breast make the male Common Redstart very distinctive © Arlette Berlie
In Switzerland, the Common Redstart is nowhere near as “common” as its close relative the Black Redstart. In the north, numbers have declined over the past 20 years, whereas in the south, they have tended to increase (Knaus etal 2018). It is found up to 2200m a.s.l, and prefers thin woodlands with patches of open ground. This can include suburban gardens: in Geneva, where a monitoring and conservation programme has been put in place, gardens with high biodiversity provide the most favourable habitat (Bossus 2017). The dramatic population declines in the north have occurred between 300-900m, and are probably due to the loss of traditional orchards, and increasingly intensive grassland management. Above 1000m populations have increased slightly (Knaus et al 2018). Overall numbers have probably also been driven down by drought in the Sahel affecting their winter quarters.
Female Common Redstarts are mostly brown, with red rump and tail and small white markings around the eye © Frank Jarvis
For a bit more background on this piece you can find more in my Sound Diary. My description and analysis of the song of the Common Redstart in this article is based on, and has been inspired by, the work of André Bossus who conducted a study in Geneva over a period of 30 years (Bossus 2019).
The broad characteristics of the song of the Common Redstart have been well documented in the past (see Cramp etal 1988; Comolet-Tirman 1994). But, before I get into the details, watch this 50 sec sample from a longer song sequence and see if you can spot any patterns:
The whole song sequence consists of a series of short strophes, usually of about 2 sec duration, separated by a gap of between 4-7 secs. Did you notice that each strophe in the above example starts off with 3-4 notes that all sound pretty similar to each other, but finishes with a “creative phase” that are less consistent? This is because each strophe can be divided into two parts: a “reasonably fixed” introduction of around 0.5 secs and a very variable creative part which is usually around 1.5 secs - this all happens pretty quickly you realise (see below following Bossus 2019).
The four opening strophes of the Common Redstart song shown in the full sonogram above, with strophe 1 expanded to show the Introduction phase and the Creative phase (after Bossus 2019)
These two phases contain important information for the song of the Common Redstart, the first can identify an individual singer just like a fingerprint and the second contains mimicry of other species delivered at high speed with amazing accuracy, so read on and let’s look at each phase in detail:
INTRODUCTION phase:
I found 8 variants of the Introduction phase from 535 strophes I recorded from two individuals, each with unique but consistent elements in them. See the illustrations below (the identification letters have no significance other than the order I discovered them in as I examined the sonograms):
Introductory motifs showing the common starting whistle and following notes. The following notes can vary in number, an example of variant “a” with 2 and 3 notes is shown.
More introductory motifs
With only one exception, they all begin with a short whistle which is consistent at 4.2 kHz; the exception is variant “c” which has a lower note at 3.4 kHz, followed immediately by a higher one which descends from 4.8 - 3.8 kHz (see above). To complicate matters further, the number of notes following the first whistle can differ within each variant (see an example in variant “a” above). All the notes are delivered very rapidly - in 1 sec or less and the variants are all so similar in tone that they are extremely difficult for the human ear to tell them apart in the field - at least to my human ears! This is what they sound like, in the same sequence as the sonograms above:
The patterns of the introductions were so clear and consistent that I quickly learned to tell them apart visually from their sonograms.
I had recorded two Common Redstarts on two days: on Day 1 I had focussed on Bird 1 (B1), and then, 8 days later, I revisited the site and got more recordings of B1, then discovered Bird 2 (B2) and made recordings of that also. In total this gave me 535 strophes which I could examine - this sounds like a lot, but is very small sample compared with the study of Bossus (2019) which sampled 150 individuals over a 30-year period. From that study, André Bossus suggested that the pattern of introductions used was characteristic to individuals and I wanted to test this to see if that applied to my two birds.
As can be seen from the table and chart above, there was a clear difference between the two individuals. Across the board, Introduction variant “a” was used 62% of the time, second was “a1” at 15% (table grey column). Overall, B1 used 4 calls: variant “a” 73% of the time, and “a1” 14 %, there being only small variations between the two days of my recording. These two variants accounted for 87% on each day. B2 on the other hand had it’s most frequent Introductions spread across 4 call variants: “a”, “a1”, “d” and “e”, plus it utilised calls “f” and “g” which, along with “e”, were not used by B1 at all in my sample. I have marked the table above in green where the clearest differences between these two individuals lies, and it becomes even more clear in the chart. So, it would seem that the proposition of Bossus (2019) applies to the birds at this site also. The location was 40km from Geneva where Bossus was working. B1 and B2 had territories 600m apart, both in open woodland, separated by a valley with pasture.
So, on to the second part: the “creative” phase.
2. CREATIVE PHASE:
The second part of the song strophe is referred to as the “creative phase”. This is because it is hugely variable both within and between individuals, and is characterised by amazing mimicry of other species. However whilst mimicking other species, they do not copy the whole song, but simply steal odd elements here and there. Let’s analyse a single strophe in detail and you can see what I mean (better to let it play 2-3 times):
To the left of the red line is the Introduction phase described already - the usual flat whistle followed by 3 notes of the variant “a” in this case. To the right of the red line is the creative phase with 3 motifs: (1) is marked unknown (to me!) (2) is the “chup-chup” of a Blackbird and (3) is very clearly two elements of a Chiff Chaff. But it all happens very fast, the whole strophe is only 2 secs long, the Introduction phase 0.8 sec and the Blackbird 0.3 secs and Chiff Chaff 0.4 secs. You’ve got to be fast to keep up with these guys!
Here is another one which has only two mimic motifs in it (I think!) - Starling and Treecreeper. (Although is that very high note in the Starling something else? Starlings make a whole range of noises and are mimics themselves, so this brings a new complexity…..)
The mimicry is not easy to pick up in the field as everything happens so fast. But by carefull examination of the sonograms of 535 song strophes I was able to identify elements of the song of the following 30 species (in no particular order):
Willow Warbler, Chiff Chaff, Wren, Tree Sparrow, Wheatear, Skylark, Nuthatch, Mistle Thrush, Greenfinch, Blackbird, Stonechat, Robin, Starling, Great Tit, Blue Tit, Crested Tit, Willow Tit, Chaffinch, Tree Pipit, Bee-eater, Black Redstart, Wood Warbler, House Martin, Black Woodpecker, Tree Creeper, Goldcrest, Nightingale, Long-tailed Tit, Swift, Bullfinch.
I have not listed how frequently each of these occur, as the list is undoubtedly biased by my own ability to recognise the elements, and I am sure I have missed some. Certainly I found several elements that occurred frequently that I could not ascribe to any species that I knew. But some were clearly used more than others: favourites were Greenfinch (three different elements were used - see below), Chaffinch, Starling, Bee-eater, Chiff-chaff. They are, on the whole, very good at the mimicry: just copying part of an element and then moving quickly to another. Here are a few comparisons of a variety of species; the Redstart comes first in each pair:
It is clear that this little bird is pretty expert at reproducing the sound of other species, and it can do so very rapidly delivering elements borrowed from 2 or even 3 species within the space of a single strophe of 1-2 secs.
3. WHY MIMICRY?
About 30 species of European birds can mimic other species, and some even mimic man-made sounds. But why would they do this, and from where and how do they learn them ? Kroodsma (in Marler and Slabbekoorn 2004) concludes that there is no one functional explanation to explain various types of mimicry, but several hypotheses are possible.
One idea that we can quickly rule out for the Common Redstart is that, by mimicking birds of prey, a species can scare away other species and make an area appear unattractive for competitors. However I did not find any birds of prey imitations in my small sample and neither did Bossus (2019) in his much larger set. So what else could be going on?
Two main purposes of song are (1) to defend territories and (2) to attract mating partners. It has been proposed that mimicry can play a role in both these functions. It was shown some years ago that song was important in territory defence, and not only that but that a bigger repertoire size was more effective in keeping out potential competitors. This was rather jokingly called the “Beau Geste” hypothesis, after the book of the same name (Krebs 1977). Field experiments with Great Tits showed it held true (Krebs, Ashcroft and Webber 1978). The basic idea is that territory holders move around singing different versions of their song to create the impression that there were already a high density of Great Tits in occupancy, and so the area would be unattractive to birds seeking to invade. Birds with a larger repertoire had more options to do this, and were more successful at defending territories. Extending this idea, it is possible that mimicry is one way of increasing the species repertoire, creating the illusion that the territory is crowded and so could reduce competition with other species as well as its own. In recording my two Redstarts, I noted they would change their song posts regularly, and only very rarely was the same creative phase delivered twice in a row.
However, the puzzling thing for me is why “my” birds chose to mimic the Common Swift, or the European Bee-eater ? Both are arial feeders, the latter is not present in the location I recorded, and the former passed overhead only occasionally. Furthermore, Bossus (2019) suggests that they may also learn from birds in Africa during their winter sojourn, as has been shown for Marsh Warblers (Dowsett-LeMaire, F. 1979). This may account for the sounds I saw used often but could not identify, but is of no help in reducing competition in the Swiss Jura!
The males use wing fluttering as well as song in courtship displays © Arlette Berlie
So this may point to another, and perhaps more likely reason for mimicry in Common Redstarts: to achieve a larger repertoire with which to attract females. Kroodsma (1976) showed that female Canaries built nests faster and laid more eggs when exposed to larger song repertoires of males, and Vallet etal (1998) were able to isolate the exact song components that created the stimulation. Subsequent studies in other species have shown that more varied repertoires are better at attracting females, and in Sedge Warblers males with large repertoires hold larger territories and are better fathers in feeding their young (Buchanan & Catchpole 1997, Buchanan & Catchpole 2000; Catchpole and Slater 2008). Song learning may come at a cost to the male, and may demand more brain power to do so, but it may also demonstrate which males may make better mates.
Both of the above hypotheses point towards the reproductive advantages of a larger song repertoire, and mimicry may be just one (cheaper?) route towards developing this. There are many species that have large repertoires that do not mimic (see Song Thrush, or Blackcap), so the strategy is not exclusive, and may only be suitable under certain circumstance or for certain species.
Redstart filed sketches by Frank Jarvis
© Arlette Berlie
However, whatever puzzles the life of this pretty little bird throws up, we can still simply sit back and enjoy its stream of music. Here is a long piece from B2 on a warm June day with plenty of insects and Woodpigeon, Chaffinch, Blackcap, Coal Tit and probably a few others in the background. Who guess at the information conveyed in these warbled little phrases?
