Mark J. Grantham

Recruitment and survival of immature seabirds in relation to oil spills and climate variability

1. In long-lived animals with delayed maturity, the non-breeding component of the population may play an important role in buffering the effects of stochastic mortality. Populations of colonial seabirds often consist of more than 50% non-breeders, yet because they spend much of their early life at sea, we understand little about their impact on the demographic process. 2. Using multistate capture-mark-recapture techniques, we analyse a long-term data set of individually identifiable common guillemots, Uria aalge Pont., to assess factors influencing their immature survival and two-stage recruitment process. 3. Analysis of the distribution of ringed common guillemots during the non-breeding season, separated by age classes, revealed that all age classes were potentially at risk from four major oil spills. However, the youngest age class (0-3 years) were far more widely spread than birds 4-6 years old, which were more widely spread than birds aged 6 and over. Therefore the chance of encountering an oil spill was age-dependent. 4. A 2-year compound survival estimate for juvenile guillemots was weakly negatively correlated with winter sea-surface temperature, but was not influenced by oil spills. Non-breeder survival did not vary significantly over time. 5. In years following four oil spills, juvenile recruitment was almost double the value in non-oil-spill years. Recent work from Skomer Island showed a doubling of adult mortality associated with major oil spills, which probably reduced competition at the breeding colony, allowing increased immature recruitment to compensate for these losses. We discuss the implications of compensatory recruitment for assessing the impact of oil pollution incidents.

Declining rates of ring recovery in British birds

A major focus of national ringing schemes is the large‐scale analysis of survival rates, primarily from recoveries of birds found dead. We demonstrate, based on analyses of birds ringed in Britain and Ireland between 1960 and 1998, a pronounced and consistent decline in the numbers of ringed birds found dead and reported across a wide range of species with diverse ecologies. The extent of these declines can, in some cases, be explained by factors pertinent to particular species, but most appear to stem from changes in reporting behaviour. Continued declines in recovery rate will reduce the precision with which we can estimate survival rates, but use of new web‐based technologies may help reverse this decline.

Cetti's Warbler Cettia cetti: analysis of an expanding population

Capsule Productivity in the UK Cettis Warbler population is constant, but overwinter survival has become increasingly dependent on winter temperatures. Aims To demonstrate how constant effort (CE) ringing can be used to estimate productivity of breeding populations, using the expanding Cettis Warbler population as an example. Methods A logistic generalized linear model is developed from an established method of estimating abundance to generate an annual index of productivity from CE catches. Dispersal of birds from ring–recapture data is modelled using a simple exponential model of dispersal. Results The number of Cettis Warblers on CE sites has increased markedly, particularly since 1998, but productivity has remained largely constant. The rate of population increase has slowed in recent years, in part because of an increasing sensitivity of the population to cold winters. Juveniles disperse further than adults, and the distance over which they disperse has increased. Conclusions CE catching provides a way of easily measuring whole-season productivity. The future of Cettis Warblers in Britain looks secure, but the population may be approaching its maximum size under current conditions.

Bird ringing in Britain and Ireland in 2003

This is the 67th annual report of the British Trust for Ornithologys Ringing Scheme, covering work carried out, and data received, in 2003. During the year, reports of ringed birds were used to assess the post‐release survival of rehabilitated individuals. Varying proportions of different species were able to re‐enter the population, with Mute Swan Cygnus olor being the most successful. The origins and age structure of Guillemots Uria aalge ringed in Britain & Ireland and found dead after five major oil spills in European waters were found to vary depending on the location of the oil spill. More immature birds and birds from eastern colonies tended to be found after spills that were further south, whereas spills in the north had a greater effect on adults and birds from western colonies. Work on mass gain strategies in Blackbirds Turdus merula showed that they put on mass in winter, when the threat of starvation is greatest, as well as changing mass through the day, again probably in response to the likelihood of starvation. A study of the survival of passerines in the few weeks after fledging found that the survival rate during this critical period is only aboutone sixth of the rate in the rest of the first year of life. A study of the demography of Spotted Flycatcher Muscicapa striata showed that changes in post fleding survival were the most likely mechanism for the observed population decline. Data gathered as part of the Constant Effort Sites (CES) Scheme showed that adult abundance among resident species was generally high, following a good breeding season in 2002. When compared to 2002, fledgling productivity in 2003 was lower, probably as a resultof cold, wetweather during the breeding season. A total of 111 Retrapping Adults for Survival (RAS) studies submitted data covering 43 species. Target species for future workwere identified. Continuing work on the winter movements of farmland passerines showed variations in the distances moved by different species. Over 11,000 Swallows Hirundo rustica were ringed aspartofthe Swallow Roost Project. The total number of birds ringed (848,532) increased for the second year and was 5% above the mean of the previous five years (1998–2002). The recovery total (11,554) was also 5% up on the five‐year mean (1998–2002). Recoveries of 180 BTO‐ringed birds and 76 ringed abroad are presented in the report; those included confirm known or suspected movement patterns or are unexpected movements.

Changes in ring recovery rates over the last 50 years: shall we continue to ring ducks?

Although knowledge of ring recovery rate is of crucial importance to establish demographic parameters, such as survival probability, this information is generally unknown for the dabbling ducks. The almost single existing value from the North American Mallard (Anas platyrhynchos) is thus generally applied to other species or geographic areas, even though this assumption may be strongly misleading. In the study reported here, we have relied on a proxy for actual ring recovery rate, namely, the proportion of rings fitted each year that were eventually reported, to test for differences between duck species (Mallard and Teal Anas crecca) and between countries [England (UK) and France] for Teal. Potential trends over time (1952–2005) were also assessed. Ring recovery rate was found to have sharply decreased and at a similar rate over time in both species in France, and in both countries for Teal (e.g. from 22.7% in 1952 to 7.2% in 1992 for the British Teal). Teal rings were, however, reported more frequently than Mallard ones, and Teal rings were more frequently reported in the UK than in France. In recent years, a phone number for reporting the information has been included on the bird mark, with the immediate result of a doubling in the recovery rate in France. Adaptations to current ringing procedures that would improve ring reporting would appear to be necessary in the future if researchers are to keep ringing as a valuable source of information for bird demography studies.

Bird ringing in Britain and Ireland in 2004

This is the 68th annual report of the British Trust for Ornithologys Ringing Scheme, covering work carried out, and data received, in 2004. During the year, changes in bird survival in relation to winter weather were studied. In almost all cases, there was a greater influence of weather on first‐year than adult survival. A paper providing guidelines to help those setting up demographic monitoring schemes for waders was produced, with ringing as a key component. Concern about a reduction in reporting rates of ringed birds led to a study of the changes. Declines were found across nearly all taxonomic groups and may reflect a combination of changes in reporting behaviour, ringing behaviour or bird behaviour. A study of the timing of muirburning used the ringing dates of pulli in conjunction with nest record data to assess its possible effect on breeding birds. There appears to be little reason for differences in cut‐off dates for muirburning in different regions and at different altitudes, but further work is required to quantify more fully the effects on moorland birds. Data gathered as part of the Constant Effort Sites (CES) Scheme showed increases in the numbers of adults of several, mainly migrant, species, possibly as a result of high rainfall in Africa south of the Sahara. Productivity was good for most species. Cettis Warbler Cettia cetti was added to the list of species covered and a study of habitat on CE sites showed that vegetation management mitigates the effect of habitat progression on catching rates. Data for 117 Retrapping Adults for Survival (RAS) studies were submitted. Over 12,000 Swallows Hirundo rustica were ringed as part of the Swallow Roost Project. The total number of birds ringed (881, 920) was the highest ever, showing an 18% increase on the mean of the previous five years (1999–2003). The recovery total (11,930) also increased (by 9% compared to the mean of the previous five years). Recoveries of 154 BTO‐ringed birds and 102 ringed abroad are presented in the report. They include records that confirm suspected or known migration patterns as well as the more unexpected movements

Bird ringing in Britain and Ireland in 2002

This is the 66th annual report of the British Trust for Ornithologys Ringing Scheme covering work carried out and data received in 2002. The BTO continues to work to understand the causes of bird population declines. During the year a major report on the demography of House Sparrows† and Starlings was completed. The work showed that while the decline in House Sparrows is likely to be due to a decline in the survival rate of first‐year birds, changes in productivity (the number of young birds entering the population) appear to have helped to halt the decline in recent years. For Starlings, changes in survival of first‐year birds was the best way of explaining the population decline, although changes in adult survival rate may also be implicated in eastern Britain. Work on wader age ratios showed that the proportion of juvenile waders in flocks caught in winter in Britain & Ireland may provide information about breeding success of high arctic species. Such data are hard to gather on the breeding grounds because of their remoteness and the dispersed nature of the breeding birds. A novel analysis of recoveries was able to show that the origins of Willow Warblers moving through Dungeness Bird Observatory in the autumn varied through the migration period and that the patterns of movement had changed in recent years. Data from the Constant Effort Sites (CES) Scheme showed that adult abundance in 2002 was generally lower than in 2001 following poor productivity in that year. Of nine significant changes in catches of adult birds between 2001 and 2002 eight were decreases (Blackbird, Sedge Warbler, Reed Warbler, Garden Warbler, Willow Warbler, Blue Tit, Great Tit and Chaffinch), with one increase (Bullfinch). Productivity generally improved when compared to 2001 with 18 species showing a statistically significant increase between the two years (Wren, Dunnock, Robin, Blackbird, Sedge Warbler, Reed Warbler, Whitethroat, Blackcap, Chiffchaff, Willow Warbler, Long‐tailed Tit, Blue Tit, Great Tit, Treecreeper, Chaffinch, Greenfinch, Bullfinch and Reed Bunting). Data sets for 110 studies of 42 species were submitted as part of the Retrapping Adults for Survival (RAS) Project. The number of birds ringed (791,074) increased, after the drop in 2001 as a result of some land access restrictions imposed due to Foot and Mouth Disease, and was 4% above the mean of the previous five years (1997–2001). The recovery total (11,042) was similar to the five‐year mean (1997–2001). Recoveries of 130 BTO‐ringed birds and 63 ringed abroad are presented in the report; those selected for inclusion confirm known breeding or wintering areas or migration routes and also show a number of significant or unusual movements.

Bird ringing in Britain and Ireland in 2001

This is the 65th annual report of the British Trust for Ornithologys Ringing Scheme covering work carried out and data received in 2001. As part of the BTOs production of the landmark Migration Atlas: movements of the birds of Britain & Ireland, which will review movements of birds using Britain & Ireland, novel approaches to the investigation of the movement patterns and distances were developed. These allow the objective comparison of whether different species are sedentary, short‐distance or long‐distance migrants and the investigation of differential migration between birds of different age and sex. The BTO continues to carry out a programme of work investigating the declines in bird populations. In 2001, an investigation of Song Thrush population dynamics showed that the survival rates of young birds was key in the population decline; reduction in survival rates also seemed to have driven the fall in numbers of Marsh Tits. Work on movements of waders between roosts on the Moray Basin showed little movement for most species; important information when the possible effects of disturbance are being considered. An investigation of the biometrics of the Redshank wintering on Severn Estuary found that the proportions of Icelandic and British breeders varied between sites; again an important factor in assessing the possible consequences of disturbance. A pilot project, which is investigating the collection of data on movements and demography of farmland passerines in winter is described. Data collected as part of the Constant Effort Sites (CES) Scheme showed significant changes in the numbers of seven species between 2000 and 2001. Of these, five resident species (Blackbird, Blue Tit, Great Tit, Chaffinch and Greenfinch) and one migrant (Whitethroat) showed increases. Only one species (Willow Warbler) decreased. By contrast, productivity tended to be low with 11 species, both residents (Dunnock, Robin, Blackbird, Long‐tailed Tit, Blue Tit, Greenfinch and Reed Bunting) and migrants (Sedge Warbler, Reed Warbler, Blackcap and Chiffchaff) showing significant declines. Progress on the EURO‐CES project, which aims to develop standard protocols for CES fieldwork and data capture across Europe is reported. Data sets for 86 studies of 42 species were submitted as part of the Retrapping Adults for Survival (RAS) Project. The first detailed analysis of Pied Flycatcher data from RAS‐type studies showed that survival rates vary between different areas of the country and confirms the value of this project. The numbers of birds ringed in 2001 (648,936) was 16% below the mean of the previous five years (1996–2000), largely as a result of Foot and Mouth Disease, which restricted the areas ringers had access to. The recovery total (10,692) was 6% lower than the five‐year mean (1996–2000). Recoveries of 195 BTO‐ringed birds and 77 birds ringed abroad are presented in the report and include a number of unusual or significant movements. Of particular note are the first recovery of a Great White Egret involving Britain & Ireland, the first recoveries of BTO‐ringed Honey Buzzards, a BTO‐ringed American Golden Plover recovered in Italy, an Hungarian‐ringed Knot found in England and the first foreign‐ringed Yellow‐browed Warbler (from Norway) to be reported in Britain & Ireland.

Bird ringing in Britain and Ireland in 2007

This is the 71st annual report of the British Trust for Ornithologys Ringing Scheme, covering work carried out, and data received, in 2007. In partnership with EURING, a web‐based application was developed to map migration routes of waterfowl species identified as being those with the highest potential to carry Highly Pathogenic Avian Influenza H5N1 across Europe. This application used recovery data held in the EURING database. The 25th year of Constant Effort Site (CES) ringing demonstrated how the heavy rainfall during the summer of 2007 had a largely negative effect on breeding success, with productivity of ten species significantly lower than the long‐term average, although that of four species was significantly higher. These contrasting fortunes are likely to be related to the timing of the heaviest rains in relation to breeding stage. For several species, there were also continued declines in adult abundance and there is particular concern for Sedge Warbler, Reed Bunting, Lesser Whitethroat and Linnet, which reached their lowest‐ever levels since CES monitoring began. Data for 96 Retrapping Adults for Survival (RAS) studies were submitted, covering 34 species, including six Red‐listed species and 14 that are Amber‐listed. The total number of birds ringed (786,070) was 7% lower than the mean of the previous five years. This reduction may have been influenced by the heavy rainfall in 2007, which affected breeding success of some species and may have led to fewer opportunities for ringing activities. The recovery total (13,156) was higher than the mean of the preceding five years and the number of recoveries of foreign‐ringed birds (1,368) was the highest annual total ever reported. Recoveries of 223 individual birds are presented in the report. They include unexpected movements, movements that confirm suspected or known migration patterns, and longevity records.

Bird ringing in Britain and Ireland in 2005

This is the 69th annual report of the British Trust for Ornithologys Ringing Scheme, covering work carried out, and data received, in 2005. Important research on Oystercatchers Haematopus ostralegus in North Wales showed that survival of adults, recruitment of juveniles and mass of both adults and juveniles were lower during winters when there was mechanised dredging for shellfish. A study of weight changes of House Sparrows Passer domesticus in autumn and winter found that they spread their weight gain through the day, thus potentially decreasing their risk of predation, but increasing their risk of starvation. Data gathered as part of the Constant Effort Sites (CES) Scheme showed an annual increase in adult numbers for five species (one migrant and four residents) and an annual decrease for five species (four migrants and one resident). Productivity was variable with 11 species having above‐average productivity and 13 below‐average. Work began to develop methods to produce annual survival trends by integrating CES data from the 350 sites that have taken part in CES over the last 21 years. Data for 110 Retrapping Adults for Survival (RAS) studies were submitted. Over 13,000 Swallows were ringed as part of the Swallow Roost Project, which ran until 2006. The total number of birds ringed (873,581) was exceeded only in 2004 and was a 12% increase on the mean of the previous five years (2000–04). The recovery total (12,658) was the second highest in the last decade, being exceeded only in 2004, and was 9% higher than the mean of the previous five years. A total of 236 selected recoveries are presented in the report. They include unexpected movements and others that confirm suspected or known migration patterns.