Birds and Other Animals at Sand Martin Colonies C
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Volume 68 Number 3 March 1975 Birds and other animals at Sand Martin colonies C. J. Mead and G. R. M. Pepler INTRODUCTION One of the traditional features of the 'Notes' section of this journal has been to publish data on nesting associations. In recent years several notes have appeared concerning species breeding in the holes of Sand Martins Riparia riparia; the most recent were by Durman (1973) and Mather (1973b). During the 1960's we were both involved in catching and ringing Sand Martins during the breeding season as part of the British Trust for Ornithology's ringing enquiry into the species. We often noticed nesting associa tions with the Sand Martins, and also witnessed predation on them and on their ectoparasites. This paper summarises our observations. Many other ringers also involved with the enquiry must have collected similar information from other parts of the country, but no attempt has been made to obtain these data from them. COVERAGE AND METHODS The geographical extent of our combined experience at Sand Martin colonies can best be gauged from fig. 1, which shows the estimated number of colony visits in each county during 1960-69 (the old counties are used throughout this paper). In all nine counties with more than ten visits, at least one colony was visited regularly over a period of years. Between us, we were probably present at more than 50,000 'bird handlings' during several hundred visits to well over 100 different colonies. [Brit. Birds, 68: 89-99, March 1975] 89 90 Birds and animals at Sand Martin colonies Fig. I. Counties where the authors visited colonies of Sand Martins Riparia riparia for ringing during 1960-69. Dot sizes indicate the estimated number of colony visits in each county (The number of visits in Berkshire should be shown in the 10-24 category, not 25-99) Most of the colonies were in man-made situations, generally actively worked sand quarries, and, except in Scotland and Wales, hardly any were discovered in 'natural' sites. The normal ringing practice was to erect mist-nets in front of the holes at night to catch the birds emerging in the morning. Extensive experiments before the start of the national enquiry had shown that this technique was most effective and that, provided that the birds had not been dis turbed during the excavation phase of the breeding cycle (generally completed during the first part of May), it did not cause the Sand Martins to desert. The nets were removed from the holes while the first catch was ringed and recorded, and were then re-erected for a second catch. These techniques allowed birds of any species occupy ing Sand Martin holes to be caught and examined, and also meant Birds and animals at Sand Martin colonies 91 that the ringers were present at, or very near, the nesting burrows for a considerable part of the time spent at the colonies. NESTING ASSOCIATIONS The most obvious nesting association involved another species breeding within an occupied colony in unmodified Sand Martin bur rows. In the case of species which actively excavate their own bur row, nothing short of continuous observation could prove whether or not the hole being used had been dug initially by a martin. The systematic list that follows does contain examples of perfect burrows being used by other species, but several instances refer to imperfect, relict holes being utilised by rather unlikely birds. In all cases, since the actual nesting chamber of the Sand Martin, whether still at the end of a burrow or exposed by erosion, was probably being used by the intrusive species, it would be quite possible for parasites normally associated with the martins (see page 94) to be transferred to other hosts. For instance, the tick Ixodes lividus has been taken from Tree Sparrows Passer montanus occupying Sand Martin burrows (S. F. Barnett in litt.). We have not conducted a search of the literature, which contains many records of nesting associations (for example, The Handbook included 'Sand Martin's burrow' among recorded nest sites of the Wryneck Jynx torquilla); all are from our personal experience. Perhaps one exceptional species might be mentioned, though our only direct experience of its nesting with Sand Martins was at Zaragoza, Spain: the Bee-eater Merops apiaster. The 1955 nesting record from Sussex (Barham et al. 1956) was from a Sand Martin colony at which one of us subsequently ringed. In most cases, the list that follows gives the number of colonies within each county where the species in question was recorded (one colony where no number is specified). In many instances, several pairs of the intrusive species were present in a single colony; also, species were often present for several years. Kestrel Falco tinnunculus: Norfolk (two); Dorset, Hampshire and Suffolk. In all cases the nests were in greatly enlarged holes or rifts in the colony face. In two instances the enlargements were probably caused by children playing, but the other nests were in holes either enlarged by the effects of the weather or, possibly, caused by animals before the pit was excavated. The nests were all situated well into the face; it is doubtful that an exposed Kestrel nest in an active colony could be successful, as the occupants would be mobbed continuously by the martins as long as they were in sight. Stock Dove Columba oenas: Hampshire, Norfolk and Suffolk (several in each); Bedfordshire (three); Berkshire, Dorset and 92 Birds and animals at Sand Martin colonies Oxfordshire (two each); Cambridgeshire, Huntingdonshire and Sussex. This species was often present in surprisingly narrow holes within the main part of a colony. Sometimes several pairs were nesting at one site. One Suffolk colony had four pairs in the face occupied by Sand Martins and at least a further four down burrows of Rabbits Oryctolagus cuniculus, all active at the same time. Little Owl Athene noctua: Hampshire (two); Bedfordshire and Norfolk. In all cases the occupied hole was at the edge of the colony. Although one of the Hampshire holes had probably been enlarged by human digging, the others were probably 'natural'. Kingfisher Alcedo atthis: Berkshire and Hampshire. In both cases the presence of a Kingfisher nest at the colony was probably fortuitous, the conditions for one species to be able to dig its burrow being suitable also for the other. One nest was directly over water, and suitable streams for the birds to fish in were within easy reach. Jackdaw Corvus monedula: Hampshire (two); Berkshire, Cambridge shire, Dorset, Norfolk, Perthshire and Suffolk. Large holes at old colonies were often regularly occupied from year to year. At the Norfolk colony four or five pairs were sometimes present. Great Tit Parus major: Hampshire (four); Norfolk and Suffolk (three each); Bedfordshire (two); Dorset, Fife, Nairnshire and Sussex. Great Tits can easily enter and use normal Sand Martin holes for nesting. All the occupied holes were at colonies with trees close at hand. Blue Tit Parus caeruleus: Oxfordshire (four); Hampshire (three); Lincolnshire and Norfolk (two each); Bedfordshire, Berkshire, Perthshire and Sussex. Even the narrowest Sand Martin hole can be used. Several occupied holes were a considerable distance from the nearest trees. Coal Tit Parus ater: Aberdeenshire, Inverness-shire, Norfolk, Perthshire and Suffolk. It is rather surprising that more Coal Tit nests were not found, since sand outcrops are often associated with coniferous trees and Coal Tits frequently nest in holes in the ground, among tree roots or, when they are available, in stone walls. Wren Troglodytes troglodytes: Dorset and Hampshire. In both cases the nesting chamber of a partly eroded burrow was used as a base for a normal domed Wren's nest. Both were at colonies in old sand- faces partly overhung by dead vegetation and roots. Blackbird Turdus merula: Oxfordshire. The exposed nesting cham ber at a badly eroded face provided a platform for a typical Black bird nest. Birds and animals at Sand Martin colonies 93 Robin Erithacus nubecula: Bedfordshire. The nest was constructed in the same situation as the two Wrens' nests described above. Spotted Flycatcher Muscicapa striata: Suffolk. The nest was built in the exposed nesting chamber of a Sand Martin burrow; although partly concealed by overhanging vegetation, it was not supported by vegetation or roots. Pied Wagtail Motacilla alba: Berkshire, Huntingdonshire, Norfolk and Oxfordshire. In all cases a partly eroded hole was used as the base for a nest. In the first two counties the nests were close to the lip of the face and among the roots of the overlying vegetation, but in the others they were partly inside crumbling holes on a sand- face free of vegetation. Starling Sturnus vulgaris Almost every well-established colony had Sand Martin holes taken over by Starlings. The only county of the 30 visited (see fig 1) where they were not found was Kincardineshire, where only one colony was visited. In our experience newly dug holes were never taken over by Starlings, as their breeding season starts so much earlier than the Sand Martins. However, holes from previous years were available; if the sand-face had survived the winter, at least one burrow was usually taken over by Starlings. Some colonies housed up to a dozen pairs. House Sparrow Passer domesticus Again, most well-established colonies had some holes occupied by House Sparrows, but a few, remote from human habitation, had none. No House Sparrows were present in the few colonies we visited in Carmarthenshire, Kin cardineshire, Midlothian and Morayshire. This pugnacious species is probably able to dispossess Sand Martins but, as with the Starling, most pairs are likely to be 'in residence' before the martins are showing serious interest in the colonies.