The effects of intensive agriculture on the breeding of the lapwing (Vanellus vanellus L.)
Changes in modem agriculture have been shown to have detrimental affects on those bird species whose populations mainly inhabit the wider countryside. Recently extensive changes to the farmed landscape have occurred through implementation of European agricultural policy much of which has been concerned with decreasing agricultural production. Lapwing (Vanellus vanellus), with almost the entire British population breeding on farmland, is a species that is thought to have been particularly affected by agricultural change. A study attempting to assess the impact that modern, intensive arable farming had on a breeding population of lapwing was undertaken from 1995 to 1997 in south-west Lancashire. The study site had an open character and was predominantly winter farmed (cultivation occurring September-February)although more than a third of the area was spring cultivated. Permanent pasture and rotational set-aside (RSA) accounted for about 2% and 5% of the cropped area respectively. Lapwings preferred to nest in spring farmed fields and RSA. The overall nest survival was 55.5% and did not differ significantly between years. Hatching success was highest in RSA (88%), lowest in spring farmed fields (48.4%) and intermediate in winter farmed fields (57.2%). Hatching success was significantly higher in spring farmed fields than in other habitats but did not differ significantly between winter and spring farmed fields. The hatching success of winter farmed fields was elevated by the success of nests of fields cultivated late in the winter. The main cause of nest losses was farming operations which caused 77.4% of all nests lost. Predation accounted for 14.4% of nest losses and desertion for 8.2%. There were annual differences in nest destruction in winter farmed crops caused by differences in the timing of agricultural operations. Nest destruction was highest in unsown fields but was compensated for by a high rate of replacement and high hatching success in replacement clutches. Two types of crop were spring farmed, combinable (mainly cereals) and vegetable (mainly potatoes) crops. Higher hatching 2 success in spring cereals than in vegetables was related to the differing intensities of management between the two crop categories. Lapwing preferred to nest in dense aggregations and far from ditches both of which reduced the risk of predation. Low densities of nest predators were maintained in the study area by predator control. Chicks from larger eggs survived better than chicks from smaller eggs. Chicks undertaking movements from natal to rearing fields suffered high levels of mortality. Chick mortality was caused by poor body condition, entrapment in field boundary ditches or predation or from the interaction of these factors. Brood movements were influenced by the distribution of crop types. Spring farmed fields and pasture were used for rearing broods. Predation was the main proximate cause of mortality for radio-marked chicks and accounted for 52% of all losses. Predation was a significant mortality factor until chicks were at least 20 days old, whereas poor body condition (31 % of all radio-marked chick losses) and ditch entrapment (17% of all losses) only killed very young chicks. Fledging success or hatching success is thought to be the main limit on productivity. Dietary studies revealed chicks ate mainly beetles but their diet varied depending upon rearing location. Surface living chick prey was abundant throughout the season in arable fields and late-hatched chicks suffered higher mortality than those hatched earlier mainly due to an increase in predation late in the season. Recommendations to maintain or improve the conditions for breeding lapwing within the study site are discussed. They include proposals which could operate under the agrienvironment regulations of the CAP, such as an increase in the area spring farmed with the cultivation of both cereal and vegetables and changes to the management of rotational set-aside to make such fields more suitable for brood rearing.