Common 34. Riparia riparia

Centuries ago, major rivers in Europe were largely untamed. Catastrophic fl oods, sweeping away bridges, houses, mills or even entire villages, created new banks. In those days, the more appropriate name for Sand Martins would surely have been Bank – even today, large rivers in eastern Europe, like the Bug, Narew, Vistula, Danube and Tisza, harbour huge colonies along their banks. The soft warbling twittering of the hawking Sand Martin along rivers links and location inseparably, but nowadays, in most of western Europe, the Sand Martin is associated with pits and quarries for sand and gravel extraction, breeding even where heavy machinery is in use daily. Ironically, economic growth has boosted Sand Martin habitat, for in this part of their range, the species rarely breeds in natural sand cliffs. This habitat change in turn has led to popular journals and manuals describing how to protect Sand Martins, how to create artifi cial sand cliffs, and even how to build concrete walls with prefabricated burrows. Protection in the breed- ing habitat, though, is not enough, for it is the rainfall in Africa that holds the key to Sand Martin survival.

396 Living on the edge Breeding range winter, from where the return migration would be initiated. This presumed movement of the wintering population is surmised on A small hirundine, the Common Sand Martin is common and wide- the basis of a wide distribution of ringing recoveries across north- ly distributed over much of Europe, particularly so in the floodplains ern Africa in March to April (Wernham et al. 2002), but is contra- and lowlands of western and eastern Europe. Large wetlands are im- dicted by a similar spread in autumn recoveries in Europe (SW-SE), portant as foraging and roosting areas. The species is multi-brood- suggesting that an unknown proportion of the British Sand Martin ed when onset of breeding is early. In spring it is among the first in- population flies directly to Mali to winter. sectivorous migratory to return to Europe, although The use of discrete moulting areas in Africa, as suggested by the breeding may be postponed due to adverse weather, whether during analysis of mineral profiles (stable-isotope ratios) in feathers (Szép migration or on the breeding grounds, or to late arrival following et al. 2003b, Fox & Bearhop 2008), substantiates the use of fixed win- adverse wintering conditions. Breeding site fidelity is variable, and tering sites. The African environment is richer in various metals within- and between-season displacements of hundreds of km have than the European breeding grounds, resulting in a finer-tuned el- been recorded (even when breeding sites remained intact; Leys emental composition in African-grown feathers, and this adds fur- 1987). The European population in the 1990s was estimated at 5.4- ther weight to the idea of Szép et al. (2003a) that the use dis- 9.5 million pairs (BirdLife International 2004a). Sand Martins are crete moulting areas during winter; their analysis of trace elements entirely migratory, wintering in sub-Saharan Africa (western popu- in feathers showed that Spanish, Danish, British and Hungarian lations) and eastern Africa (eastern populations). populations differed markedly in elemental composition, achieva- ble only if these populations used different moulting areas in Africa. Using tail feathers from the same individual in its first and second Migration

Sand Martins breeding in western, central and much of northern Europe generally migrate on headings between SW and S, but the more easterly European populations tend towards S and SE. They do not avoid either the Mediterranean Sea or the Sahara; recoveries from Algeria and Libya show that the Sahara is crossed in broad front (Fig. 233). Given the outward migration headings of northern, central and eastern European birds (Fig. 233), the central Sahel seems to be a major wintering domain of these populations, from the Inner Niger Delta through to Lake Chad, but another such area extends into east- ern and southern Africa. There have been very few recoveries from these regions to substantiate this hypothesis; a Swedish was re- covered in Mali (Fig. 233) and birds from Norway have been recov- ered from Senegal (1), Mauritania (1), Nigeria (1), Congo (1) and South Africa (11) (Bakken et al. 2006). The recoveries of birds in the Central African Republic (one each from Finland, Sweden and Den- mark) suggest that, in line with the sparse Norwegian data, many which are northern breeders continue overland to wintering areas in South Africa. Russian and Ukrainian Sand Martins presumably win- ter mainly in eastern and southern Africa (Cramp & Simmons 1988). Based on ringing data, West European birds, and particularly those from Britain, end up in the westernmost part of West Africa, i.e. in the Senegal Delta. Of the >15 000 Sand Martin ringed in Sen- egal (Sauvage et al. 1998), 86 were recovered from Great Britain, 20 from Ireland and 11 from The Netherlands. This western European Fig. 233 European ringing locations of 870 Sand Martin recovered component is increased by recoveries from Portugal, Spain, France, (n=132) or ringed (n=738) between 4° and 37°N (From: euring). In order Germany and Denmark. Cramp & Simmons (1988) and Wernham et not to clutter the figure, lines are not shown for birds ringed or cap- al. (2002) suggested that the Sand Martin appears to be systemati- tured in the Senegal Delta; instead, red dots indicate ringing sites of cally nomadic, with British birds moving east from coastal sites in birds recaptured in Senegal (n=123) or birds ringed in Senegal and re- Senegal through the Sahel to the Inner Niger Delta in Mali during captured later on in Europe (n=473).

Common Sand Martin Riparia riparia 397