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Summary1. Whilst the widespread declines in breeding grassland waders in many parts of Europe have been associated with changes in agriculture, there is concern that predation may compromise recovery of wader populations, even in situations where habitat is suitable, such as nature reserves managed for breeding waders.2. An 8-year cross-over experiment was used to examine the effect of red fox Vulpes vulpes and carrion crow Corvus corone control on breeding performance and population trends of lapwing Vanellus vanellus on 11 lowland wet grasslands. 3. Predator densities in the absence of control measures were highly variable among sites, and consequently the numbers of predators removed were similarly variable. Overall, predator control measures resulted in a 40% decline in adult fox numbers and a 56% reduction in territorial crows. 4. There was no overall effect of predator control on the failure rate of 3139 lapwing nests. However, the effect of predator control varied significantly among sites, reflecting the variation in predator densities. Predator control measures were more likely to result in increased nest survival at sites where predator densities were high. 5. Nest-temperature loggers deployed at seven sites indicated that 88% of nest predations occurred during darkness, suggesting nocturnal mammalian predators. 6. At seven sites predator control had no overall effect on chick survival, monitored by radio-tracking 459 chicks, but there were differences in the effect of predator control among sites. Densities of predators were low during years without predator control measures at the majority of these sites. 7. At six further sites breeding success, assessed from the proportion of adults accompanied by young late in the season, was twice as high in years when predators were controlled. 8. There was no overall effect of predator control on lapwing population trends across the experimental sites. 9. Synthesis and applications . This study highlights the need for information on predator densities and the impact of predators on nest and chick survival, before embarking on predator control measures at a particular site. A decision tree for determining the circumstances in which fox and/or crow control may be both necessary and effective is recommended.

The importance of sympatric speciation (the evolution of reproductive isolation between codistributed populations) in generating biodiversity is highly controversial. Whereas potential examples of sympatric speciation exist for plants, insects, and fishes, most theoretical models suggest that it requires conditions that are probably not common in nature, and only two possible cases have been described for tetrapods. One mechanism by which it could occur is through allochronic isolation-separation of populations by breeding time. Oceanodroma castro (the Madeiran or bandrumped storm-petrel) is a small seabird that nests on tropical and subtropical islands throughout the Atlantic and Pacific Oceans. In at least five archipelagos, different individuals breed on the same islands in different seasons. We compared variation in five microsatellite loci and the mitochondrial control region among 562 O. castro from throughout the species' range. We found that sympatric seasonal populations differ genetically within all five archipelagos and have ceased to exchange genes in two. Population and gene trees all indicate that seasonal populations within four of the archipelagos are more closely related to each other than to populations from the same season from other archipelagos; divergence of the fifth sympatric pair is too ancient for reliable inference. Thus, seasonal populations appear to have arisen sympatrically at least four times. This is the first evidence for sympatric speciation by allochrony in a tetrapod, and adds to growing indications that population differentiation and speciation can occur without geographic barriers to gene flow.Oceanodroma castro ͉ phylogeography ͉ genetic isolation ͉ seasonal populations ͉ storm-petrel

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. British Ecological Society is collaborating with JSTOR to digitize, preserve and extend access to Journal of Animal Ecology. Summary 1. The use of supplementary feeding experiments to investigate the relationship between food supply and clutch and egg size in birds has yielded disparate results, some authors showing an advancement in laying date and/or increased clutch size in response to additional food whereas other studies have found no effect. 2. Here we investigate the nutritional requirements of egg formation in lesser blackbacked gulls Larus fuscus L., through a series of feeding experiments providing additional food of different quality. 3. Provision of additional food on the nesting territories did not result in a decrease in the amount of time spent away from the colony by females, although fish-fed males did spend more time on territory during the early part of the pre-laying period in a year of normal food supply. 4. Courtship feeding rates were very low in comparison with other studies and were not influenced by provision of additional food. 5. Providing either supplementary fish or fat during the pre-laying period demonstrated that in a year of apparent low food availability, clutch size was depressed by protein, but not energy, limitation. A second experiment, supplying either fish or cooked egg to pre-laying birds, suggested that in addition to these general protein requirements, egg production may further be limited by the supply of specific nutrients, contained in the egg, but not present in sufficient quantity in the fish supplement. The possible identity of these specific nutrients is discussed. 6. There was no advancement in laying dates of fed birds compared with controls in the same year. This contrasts with studies on other species and suggests that clutch size may not be primarily determined by laying date in lesser black-backed gulls. 7. Chicks hatching from the eggs laid by females receiving an egg supplement prior to laying tended to be skeletally larger and heavier on hatching, but any potential advantages of hatching from larger eggs were short-lived. There was no difference in subsequent growth or survival of chicks of egg-fed parents compared with controls.