J. H. Marchant

The demography of the decline in the British willow warbler population

Since 1989, there has been a major and unprecedented decline in the breeding population of willow warblers ( Phylloscopus trochilus ) in southern Britain. Between 1986 and 1993 the numbers of willow warbler territories counted on monitoring plots declined by 47% in southern Britain, compared to a decline of 7% in northern Britain. Breeding densities of willow warblers are generally higher in the north and west of Britain, than in the south. Data from nest record cards provided evidence of only minor regional differences in breeding performance with a small but significant increase in the loss rate of nests during the nestling stage in 1989-1992 in southern Britain, compared with 1974-1988. Mark-recapture data collected at 18 constant effort sites and from one intensive study were used to estimate apparent survival rates of adults during the period 1987-1993. Program SURGE4 was used to test for differences in survival rates and recapture probabilities between years, sexes, sites and regions. Recapture prob...

How representative of agricultural practice in Britain are Common Birds Census farmland plots

The Common Birds Census is designed to measure year-to-year changes in bird population levels. But how representative are the sample plots of the country as a whole? What is being measured?

Bird Population Changes for the Years 1973–74

The population trends apparent in the last few years continue, with further increases in many of our small resident birds. In contrast, several of the summer visitors remain at a very low level while some, such as the Swallow, have suffered further marked decreases.

Survival rates of hirundines in relation to British and African rainfall

The BTOs Retrapping Adults for Survival scheme is designed to monitor survival rates of species of conservation concern that are monitored relatively poorly by other forms of ringing. Here we present temporal trends in survival rates for three hirundine species, Barn Swallow Hirundo rustica, House Martin Delichon urbicum and Sand Martin Riparia riparia. Estimates of apparent survival rate were similar to those found in previous studies and were correlated with rainfall on the African wintering grounds, but not with rainfall in Britain, suggesting that overwinter food resources may be more limiting.

GB Non-native Species Information Portal: documenting the arrival of non-native species in Britain

Abstract Information on non-native species (NNS) is often scattered among a multitude of sources, such as regional and national databases, peer-reviewed and grey literature, unpublished research projects, institutional datasets and with taxonomic experts. Here we report on the development of a database designed for the collation of information in Britain. The project involved working with volunteer experts to populate a database of NNS (hereafter called “the species register”). Each species occupies a row within the database with information on aspects of the species’ biology such as environment (marine, freshwater, terrestrial etc.), functional type (predator, parasite etc.), habitats occupied in the invaded range (using EUNIS classification), invasion pathways, establishment status in Britain and impacts. The information is delivered through the Great Britain Non-Native Species Information Portal hosted by the Non-Native Species Secretariat. By the end of 2011 there were 1958 established NNS in Britain. There has been a dramatic increase over time in the rate of NNS arriving in Britain and those becoming established. The majority of established NNS are higher plants (1,376 species). Insects are the next most numerous group (344 species) followed by non-insect invertebrates (158 species), vertebrates (50 species), algae (24 species) and lower plants (6 species). Inventories of NNS are seen as an essential tool in the management of biological invasions. The use of such lists is diverse and far-reaching. However, the increasing number of new arrivals highlights both the dynamic nature of invasions and the importance of updating NNS inventories.

Bird Population Changes for the Years 1975–76

The year 1976 saw decreases in many resident birds, particularly the smaller species. Both partridges made substantial increases and the Whitethroat continued to recover from the 1969 population crash, but has a long way to go yet.

Bird Population Changes for the Years 1974–75

Many resident birds are now maintaining higher population levels than was the case during the first ten years of the CBC, but some summer visitors are much less common. However, the decline in Redstart and Sedge Warbler seems to have halted.

Habitat availability and use by Turtle Doves Streptopelia turtur between 1965 and 1995: an analysis of Common Birds Census data

Capsule Breeding density on long-term CBC plots fell in proportion to loss of nesting rather than feeding habitat. Aim To investigate the habitat requirements of Turtle Dove and relate changes in breeding density to changes in habitat, at the national scale. Methods Bird and habitat data were extracted from 30 long-term farmland and woodland CBC plots for the period 1965 to 1995. Results Turtle Dove densities declined at an average annual rate of 4.6% on both farmland and woodland plots, equal to a decline of 76% over the period 1965 to 1995. Turtle Dove density on the woodland plots was, on average, 6.5 times greater than on the farmland plots. Overall habitat availability did not change over time, but some finer measures of habitat quality, such as habitat diversity, nesting and feeding habitat availability did change. Changes in Turtle Dove density were positively related to changes in the amount of hedgerow and woodland edge per unit area on the farmland CBC plots, where Turtle Dove territories contained three times more woodland than expected from availability. On the woodland CBC plots, territories were established apparently at random. Conclusion It is likely that the availability of nesting habitat dictates Turtle Dove density, with areas of woodland and scrub supporting on average 6.5-times more breeding Turtle Doves, per unit area, than farmland.

Population changes for waterways birds, 1981–1982

1981–82 was a time of changes for the Waterways Bird Survey. More stretches of river and canal were surveyed than ever before. more species were monitored and (in the wake of the most severe winter for two decades) the WBS index for several riparian birds plummeted to a record low.

Bird population changes for the years 1976–77

This paper reports on the 16th year of the Common Birds Census, and details index changes between the years 1976–1977. The largest increase noted this year was 54% for Chifichaffs on farmland (39% in woodland), while the biggest decline was one of 33% for Little Owls.