There is something really impressive about a single-species monograph that is privately published by the person who spearheaded much of the work presented inside. In this case, Ron Summers was part of a small group in Scotland who realised in the late 1960s that there were hardly any ringing recoveries of Purple Sandpipers Calidris maritima. In the decade that followed, he and others made great strides to rectify this with targeted ringing on both the east and west Scottish coasts, and now over 9,000 have been ringed. From the 1970s onwards, he also organised expeditions to find the birds breeding in Norway, Iceland and Svalbard. In addition to the data that his own studies have collected, Summers has brought together everything that is known about the species, mostly from European studies, as, by comparison, relatively little seems to have been published about the North American wintering population despite birds there being in decline.
The book is divided into 15 chapters with the last being a synthesis of everything. In addition to outlining the work in Scotland and in the various breeding areas (including the tiny UK population), there are core chapters examining the birds’ size, breeding distribution and numbers, nesting activity, migration, plus plumage and moult. For those more interested in the winter distribution and numbers, these are given a chapter, as are discussions on how these populations have fluctuated, the preferred habitats, feeding behaviour, body mass, site fidelity, local movements, survival and population dynamics.
There are many interesting facts revealed from Summers’ work and those of others. There has been a northwest shift in the winter distribution of Purple Sandpipers within the UK, which may be linked to climate change, or be because Canadian birds (which winter in northern Scotland) are doing better than those in Norway (which winter on the east coast). Declines have also been recorded in Iceland, where birds are both migratory and resident. The future is uncertain for this and other waders that rely on the tundra for breeding. This habitat is predicted to decline by between 40% and 57% by the time carbon dioxide has doubled from pre-industrial levels as boreal forest replaces it. The tundra cannot move northwards as the Arctic Ocean occupies latitudes north of 80°N. Summers warns that the 15 million breeding waders in this habitat could halve in number. In addition, on Britain’s rocky shores, sea level is predicted to rise by at least 40 cm, which will reduce the available feeding and roosting habitat. On the other hand, increased wind action may result in more seaweed being washed up, providing good feeding habitat. So, the future offers many conundrums for the fortunes of the species.
Among the other fascinating insights are discussions on the fact that – as in other monogamous small waders – females are larger than males. The relatively small males have short bills, which could be advantageous as they undertake most of the brood attendance; this possibly reduces feeding competition between the sexes, too. I have often wondered why Purple Sandpipers stop at Spain and do not migrate farther south into Africa, as Turnstones Arenaria interpres do; Summers suggests that, in the tropics, invertebrates would find the rocky intertidal zone too hot at low tide, while the coasts of Britain offer a greater tidal range and therefore more feeding opportunities.
These are just a few examples of how comprehensive this book is. It is a delight to read, being well designed and created in an engaging style. It is a summary of research that has covered more than 50 years; it is personal research at its very best; and is a reminder of how without this kind of effort we would have little idea of what is happening to our bird populations.