Common Redstart Phoenicurus Phoenicurus 427

Common Redstart 37.Phoenicurus phoenicurus

When Gerrit Wolda, a maths teacher in The Netherlands, started his research on “physiological phenomena in some bird species” in the winter of 1909, by providing 100 nestboxes in the woodland surrounding the sanatorium “Oranje Nassau’s Oord” near Wageningen, he could not have dreamed of the far-reaching impact that his initiative would have on ornithology and ecology (Bijlsma 2006a). By “physiological phenomena” he alluded to site fi delity, mate choice and reproductive strategy (more precisely: number of broods per annum; Wolda 1918). His nestbox approach was expanded to the Hoge Veluwe in 1921 by H.N. Kluijver (Kluyver 1951); a study that is still fl ourishing (Both et al. 2006), and since copied all over Europe. An unforeseen side-effect of his study was the occupation of nestboxes by Redstarts and Wrynecks. The latter were considered such a threat to other nestbox breeders (by their habit of removing the nests and clutches of tits and redstarts) that the advice given was to remove Wrynecks from nestboxes (as was to happen to Tree Sparrows half a century later - like Wryneck). As it happens, since he was above all a curious naturalist, Wolda did no such thing, but instead studied Wrynecks as the opportunity arose, unwittingly providing a wonderful calibration point for studies on this species during their declining phase in the late 20th century (Bijlsma et al. 2001). Returning to the Redstarts in Wolda’s days, and even much later when Ruiter (1941) did his studies on Oranje Nassau’s Oord in the mid-1930s, this species was second in abundance only to Great Tits. How much the world has changed since then.

426 Living on the edge Breeding range Bakken et al. 2006). Although not backed by ringing data, it is likely that central and eastern European birds winter further to the east in Redstarts occupy the boreal and warm temperate zones of Eurasia, the Sahel (Glutz von Blotzheim & Bauer 1988). essentially between the July-isotherms of 10°C and 24°C (Hagemeij The first Redstarts arrive in their wintering quarters in Senegal in er & Blair 1997). Densities increase from south to north. The Euro- the first half of September, but it takes another month before the pean population was estimated at 6.8-16 million pairs in 1990-2002 species is really abundant (Morel & Roux 1966b). This schedule fits (BirdLife International 2004a). the dates of passage as noted in NW Algeria (mid-September through mid-October, peaking early October; Bairlein 1988). They are eclec- tic in their habitat choice, ranging from very dry scrub savanna with Migration Acacia species through more humid and lush Acacia nilotica thick- ets, possessing an inextricable understorey, to park-like forests in Most African ringing recoveries are from Morocco and the Mediter- the Sudan vegetation zone. Redstarts are absent when woody vege- ranean coast of Algeria and Tunisia (Fig. 246). In total, 291 birds tation is lacking (Morel & Roux 1966b). were reported from the Atlas mountains and the relatively humid Morel & Roux (1966b) suggested that Redstarts exhibited high zone north of it, of which 16.5% occurred during the spring migra- site fidelity from mid-October onwards, because the same numbers tion (21 March-31 May), 65.7% during the autumn migration (21 Au- of birds of the same age-composition were recorded week after week gust-20 November) and only 7.4% during the 13 intervening winter at a site in Senegal, noting that the same site was used by Redstarts weeks. A surprisingly high number (n=116) were recovered from the in successive winters. However, of 136 Redstarts ringed in Senegal Sahara desert, birds which were also mainly migrants: 74.7% in in 1957-1977, only 2 were recaptured and even fewer for Redstarts spring, 14.1% in autumn and 9% from the winter period. ringed in 1985-1993 in the Djoudj: none from 140 (Sauvage et al. From the wintering areas proper, ring recoveries are scarce. Two 1998). On the coastal island of Ginak, The Gambia, site fidelity was British-ringed birds in the Senegambia were captured on 23 Octo- highly significant within each winter, but not between winters. The ber and 26 November. A Redstart in Chad was recaptured at the recurrence rate – retraps within the whole study area of c. 1 km di- same locality one month later in November. A bird ringed on the ameter – was moderate, but 4 of the 17 recurrent birds had been north coast of the Black Sea on 1 October 1991 was recovered on a small island in the Red Sea on 25 April 1996. Recoveries in Europe show that Redstarts generally follow a southwesterly migration direction in autumn (an arc of WSW-SSW), except for British birds, which first seem to take a more southerly course until they reach Iberia (Zink 1981, Wernham et al. 2002). The Mediterranean is crossed on a broad front, as attested by abundant catches in northern Egypt (60 near Alexandria from 8 September to 13 October 1965, body mass 11.5-20.7 g, mean 16.9 g; Moreau & Dolp 1970) and in northwestern Algeria (52 from 18 September to 19 No- vember 1985, body mass 11.9-19.0 g. mean 14.7 g; Bairlein 1988). The latter study showed that 40% of the birds captured for the first time had no fat; those recaptured 2-23 days later had increased their body mass on average from 13.8 to 17.4 g. Of Redstarts captured at oases between northern Africa and the wintering quarters, the average body masses and fat reserves were well above pre-migratory lev- els as measured in SW Germany (Bairlein 1992), enabling them to continue their migration without refuelling at such stopovers.

Distribution in West Africa

The winter distribution in the Sahel presumably follows more or less the same east-west gradient as in the breeding quarters (Fig. 246). In the westernmost part of the Sahel, i.e. in Senegambia, two British birds were reported, but this region may be a melting pot of Fig. 246 European origins of 502 Redstarts recovered or recaptured birds from western Europe and southern Fennoscandia (Fig. 246; between 4° and 37°N From: euring.

Common Redstart Phoenicurus phoenicurus 427