Time filter

Source Type

Durham, United Kingdom

Body masses of over 1,500 adult and sub-adult Black-legged Kittiwakes Rissa tridactyla were measured during breeding seasons from 1954 to 1995 at colonies in NE England. There was little change between years in the mean mass of each sex, except for a 2% increase in the 1980s and a decrease of 4-7% in 1995. The relative constancy of mass, together with high breeding success throughout, suggested that periods of food shortage in the breeding season were absent throughout the study period. Breeding males averaged 394g and were about 13% heavier than females (340g). Breeding females showed a brief and temporary increase in mass prior to egg laying, and both sexes showed a small but non-significant increase in mass during incubation. There was an abrupt loss of about 6% of mass in adults of both sexes at the time the eggs hatched, and mass remained at this lower level through the nestling period. Masses of prospecting and breeding females were similar and both showed the abrupt decrease in mass in late May and in June. In contrast, prospecting males had a consistently lower mass (377g) than breeding males throughout. The pattern and timing of the loss of mass in breeding kittiwakes did not support the hypothesis that it is induced by stress arising from the need to obtain extra food for the brood, but that it can be regarded as an adaptation for more energetically efficient flight during a period when increased flying activity is needed to obtain additional food for the brood. The assumption that a higher mass in an individual is always a useful measure of quality is probably unjustified.

This paper examines the reasons behind the large population explosion of the Herring Gull (Larus argentatus) in Great Britain, which started about 1900, continued for 60-70 years and was then followed by a decline in numbers. The increase has often been associated with food obtained at landfills, but it is better explained by other causes because such sites were not used for feeding until the increase had been in progress for 50 years and for less than 20 years before gull numbers started to decline. Further, the flock and frenzy method of feeding used by Herring Gulls at landfills is not well adapted for the successful exploitation of this food source, and the frequency of use has often been exaggerated. The historic increase in Herring Gulls starting in about 1900 should be attributed to protection and then food acquired from the marine environment, including fishing offal, and increased feeding on agricultural land. Culling has contributed more to the recent decline of the population than has been previously assessed because of secrecy and lack of detail about many such events. Feeding at landfills may have been detrimental to the Herring Gull population owing to increased mortality from botulism acquired there. It is concluded that culling and botulism both contributed appreciably to the end of the population explosion that occurred around 1970, and to the subsequent decline of the Herring Gull in Great Britain. The increase and continued spread of Herring Gulls nesting in urban areas in Great Britain cannot be explained by food obtained within the towns. Observations that, in some areas, most of these gulls rarely fed at landfill sites, and so avoided botulism, may account for their continued increase in urban areas. © 2015, BioOne. All rights reserved.

Mills J.A.,10527A Skyline Drive | Teplitsky C.,CNRS Science Conservation Center | Arroyo B.,Institute Investigacion en Recursos Cinegeticos IREC CSIC UCLM JCCM | Charmantier A.,CNRS Center of Evolutionary and Functional Ecology | And 61 more authors.
Trends in Ecology and Evolution | Year: 2015

The recent trend for journals to require open access to primary data included in publications has been embraced by many biologists, but has caused apprehension amongst researchers engaged in long-term ecological and evolutionary studies. A worldwide survey of 73 principal investigators (Pls) with long-term studies revealed positive attitudes towards sharing data with the agreement or involvement of the PI, and 93% of PIs have historically shared data. Only 8% were in favor of uncontrolled, open access to primary data while 63% expressed serious concern. We present here their viewpoint on an issue that can have non-trivial scientific consequences. We discuss potential costs of public data archiving and provide possible solutions to meet the needs of journals and researchers. Public data archiving is the archiving of primary data used in publications so that they can be preserved and made accessible to all online. Public data archiving is increasingly required by journals. However, the costs of public data archiving might be underestimated, in particular with respect to long-term studies. Long-term studies have been responsible for the answers to many important questions in evolution and ecology which could only be answered through following the life-histories of individuals for decades. Several papers have been published in favor of public data archiving, but a more balanced viewpoint is necessary to allow a discussion to emerge on a code of ethics and ways to preserve and protect the data, encourage the initiation and continuation of long-term studies, and meet the requirements of the whole scientific community. © 2015 Elsevier Ltd.

Coulson J.C.,29 St Marys Close | Coulson B.A.,29 St Marys Close
Bird Study | Year: 2015

Capsule: The vantage point survey methods used in the 1999-2002 surveys of urban nesting large gulls in Britain and Ireland appreciably underestimated numbers, resulting in lower national totals and exaggerated national population changes, because they did not account for a substantial proportion of undetected nests. Aims: To evaluate the efficiency of various survey methods for urban nesting large gulls. Methods: Vantage point and street surveys of Herring and Lesser Black-backed Gulls Larus argentatus and Larus fuscus nests were made in six urban conurbations and used to compare detection efficiencies. Some nests missed by both methods were later identified by the presence of unfledged chicks. In later years, the numbers of nests which were actually missed was determined by using a cherry-picker which allowed all nests to be located in Dumfries. The proportion of nests on industrial and commercial buildings was recorded. Results: Vantage point and street surveys missed an appreciable number of nests and had average maximum nest detection rates of 78% and 48%, respectively. Combining the two methods raised the efficiency to a maximum of 88%. The detection rate varied inversely with the proportion of nest sites that were on commercial or industrial sites. The complete census of nests in Dumfries in 2013-14 showed that vantage point surveys detected only 75% of nests, while the combination of the two survey methods increased the detection rate to 84%. Conclusion: Vantage point surveys markedly underestimate numbers of nesting large gulls. Surveys were less effective on conurbations where nesting gulls used a high proportion of industrial and commercial properties. Therefore the 1999-2002 national surveys in Britain and Ireland underestimated the numbers of urban nesting Herring and Lesser Black-backed Gulls and, as a result, may have exaggerated the national trends in abundance of both species. More intensive methods are required in surveys of urban nesting gulls and correction factors need to be established from very high vantage points by use of cherry-pickers or aerial surveillance. © 2015 British Trust for Ornithology.

Discover hidden collaborations