Andy D. Evans

Emerging Infectious Disease Leads to Rapid Population Declines of Common British Birds

Emerging infectious diseases are increasingly cited as threats to wildlife, livestock and humans alike. They can threaten geographically isolated or critically endangered wildlife populations; however, relatively few studies have clearly demonstrated the extent to which emerging diseases can impact populations of common wildlife species. Here, we report the impact of an emerging protozoal disease on British populations of greenfinch Carduelis chloris and chaffinch Fringilla coelebs, two of the most common birds in Britain. Morphological and molecular analyses showed this to be due to Trichomonas gallinae. Trichomonosis emerged as a novel fatal disease of finches in Britain in 2005 and rapidly became epidemic within greenfinch, and to a lesser extent chaffinch, populations in 2006. By 2007, breeding populations of greenfinches and chaffinches in the geographic region of highest disease incidence had decreased by 35% and 21% respectively, representing mortality in excess of half a million birds. In contrast, declines were less pronounced or absent in these species in regions where the disease was found in intermediate or low incidence. Also, populations of dunnock Prunella modularis, which similarly feeds in gardens, but in which T. gallinae was rarely recorded, did not decline. This is the first trichomonosis epidemic reported in the scientific literature to negatively impact populations of free-ranging non-columbiform species, and such levels of mortality and decline due to an emerging infectious disease are unprecedented in British wild bird populations. This disease emergence event demonstrates the potential for a protozoan parasite to jump avian host taxonomic groups with dramatic effect over a short time period.

Use of set-aside land in winter by declining farmland bird species in the UK

Between 1992 and 1993 over 600 000 ha of arable farmland in the UK were set aside under a production control mechanism of the Common Agricultural Policy (CAP) of the European Union. One of the management options for this set-aside land was to leave it as an over-winter fallow with a naturally regenerated green cover. This study was designed to test whether such land was used by seed-eating bird species, populations of many of which have undergone recent severe declines. Five out of six declining species recorded in the study were found in significantly greater numbers on this habitat than would be expected if the birds were randomly distributed over the farmland landscape. The results of this study, covering a wide geographical area, reinforce previous findings of the importance of winter food sources, particularly over-winter stubble fields, to declining farmland seed-eaters. Proposed changes to the CAP under Agenda 2000 include the reduction of the obligatory set-aside rate to zero. These results sugges...

Foraging habitat selection by yellowhammers (Emberiza citrinella) nesting in agriculturally contrasting regions in lowland England

Fine-scale habitat use by yellowhammers (Emberiza citrinella) searching for food to provision nestlings was compared in three agriculturally contrasting regions of lowland England. Log-linear modelling was used to test for significant overall variation in habitat use and significant differences in relative use between pairs of habitats. Yellowhammers provisioned nestlings non-randomly with respect to habitat availability. Habitat selection was found to be generally consistent across the three regions; field boundary structures and barley crops were the most selected foraging habitats, while intensively-managed grass fields were avoided relative to virtually all other habitats. The observed patterns of habitat selection are likely to result from an interaction of food abundance and varying accessibility to food, mediated by sward structure. The geographical generality of the results allows reasons to be suggested for the recent rapid population decline of the species and general conservation recommendations to be made with respect to lowland farmland.

Seasonal variation in breeding performance and nestling diet of Cirl Buntings Emberiza cirlus in England

The survival rates and outcomes of Cirl Bunting nests were recorded over a four-year period. Significant annual variations in nest survival were found at both the egg and the young stage. Significant seasonal variations in survival rates were found, with late nests being over twice as likely to produce fledglings as early ones. Most losses occurred at the chick stage early in the season and were due to predation and starvation. Chicks in poor condition through food shortage may have been more likely to be predated as a result of increased begging activity. Late season chicks had a very different diet to those hatched early in the season, being fed a much higher proportion of Orthoptera. They also enjoyed higher growth rates and survival. Rainfall had a small detrimental effect on growth rates, probably as a result of insect prey becoming hard to find. Loss of arthropods due to intensification of livestock farming and loss of diversity in the agricultural landscape may have contributed to the decline of th...

Habitat selection of Cirl Buntings Emberiza cirlus wintering in Britain

The habitat selected by foraging Cirl Buntings was investigated at 2 sites in South Devon, England in each of 3 winters. Cirl Buntings showed a marked preference for foraging on stubble or fallow fields at both sites in all 3 winters of the study. A reduction in the area of stubble fields left over winter may have contributed to the decline of the British Cirl Bunting population.

Causes of nest failure among buntings in the UK

Causes of nest failure among the four lowland buntings in the UK, Yellowhammer, Cirl Bunting, Reed Bunting and Corn Bunting, were investigated using records from 1924–¸92 held by the BTOs Nest Record Scheme. Three main types of failure were identified: nest-predation, destruction by agricultural operations (e.g. crop harvesting, cattle trampling, hedge cutting) and natural causes (e.g. rain, adult predated). Nest predation accounted for a third of nests of Yellowhammer, Cirl Bunting and Reed Bunting but was less important for Corn Bunting. Nest predation was more prevalent during the nestling stage than egg stage, and failure due to agricultural operations occurred more during the egg stage than nestling stage for Yellowhammer and Reed Bunting. Many farmland species have shown population declines since 1970, coinciding with changes in predator populations, farming practices and possibly weather patterns, and the relative importance of each cause in pre- and post-1970 samples was therefore compared. Corn ...

The status and distribution of Nightjars Caprimulgus europaeus in Britain in 1992. A report to the British Trust for Ornithology

In 1992 the British Trust for Ornithology and the Royal Society for the Protection of Birds organized a national survey of Nightjars. A total of 3093 churring males was located and the British population was estimated to be approximately 3400 males. This represents an increase in numbers of more than 50% since the last national survey in 1981. Possible reasons for this partial recovery after a long period of decline are discussed.

The numbers and distribution of Cirl Buntings Emberiza cirlus breeding in Britain in 1989

In 1989 the Royal Society for the Protection of Birds in conjunction with the Devon Bird Watching and Preservation Society conducted a survey of Cirl Buntings breeding in Devon. These data were supplemented by records from other counties to assess the current status of the Cirl Bunting in Britain. Results indicate that the long-term decline in both numbers and range has continued and that the future status of the bird as a British breeding species is in jeopardy.

Wintering Cirl Buntings Emberiza cirlus in southwest England select cereal stubbles that follow a low-input herbicide regime

Capsule Birds selected stubbles preceded by crops with reduced pesticide inputs over those grown conventionally. Aims To compare use by wintering birds of stubbles created from cereals grown under a low-input pesticide regime with use of stubbles created from cereals grown under conventional high-input pesticide regime, in order to inform agri-environment scheme development. Methods ‘Complete area search’ methods were used to compare densities of birds occupying 186 stubble fields during winter 2003/04. Plant surveys were conducted on all fields at the same time as the bird surveys, while seed samples were taken from a subset of 20 special project stubbles and 20 conventional stubbles using pairwise random selection throughout the course of the fieldwork. The data were analysed using multivariate log-linear and logistic regression methods to assess the differences in bird numbers between fields, according to stubble type and other variables. Results Cirl Buntings and several other species, including Yellowhammer and Reed Bunting, used special project stubbles significantly more than conventional stubbles. Seed densities, especially those of broadleaved weeds, were higher on special project stubbles. Conclusions This work highlights the importance of continued agri-environment payments for low-input stubbles for some declining bird species, such as Cirl Buntings.

Importance of overwintered stubble for farmland bird recovery (and reply from G.R. (Dick) Potts)

Capsule Without this prescription, populations of seed-eating passerines are unlikely to recover.