RedRoses

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These data are those used in the submission to the journal Animal Behaviour a manuscript entitled 'Size selection of worms by redshank, Tringa totanus: a multivariate re-analysis of data first published in 1977'

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The two sorts of observations used to describe foraging behaviour are detailed in Goss-Custard (1977 - Animal Behaviour 25 (1)). To measure the numbers of worms taken per unit time or per metre searched – the feeding rate – an individual was watched for 30 s of active foraging and the numbers of unidentifiable small prey and worms swallowed recorded. The length of visible worms was estimated by comparison with the length of the redshank bill. Intake rate was the product of the feeding rate and the mean weight of the consumed prey. Here we use a single function for Hediste to convert worm length to ash-free dry mass (AFDM); this is a better measure than dry weight of food value as it excludes indigestible inorganic material . A second series of observations measured the aspects of foraging behaviour required to convert intake rate – the consumption per unit time - to the biomass ingested per metre searched. The time taken to make 5 paces was measured by stop-watch and the numbers of pecks, small, unidentifiable prey and visible worms of measurable length recorded simultaneously to estimate by linear regression the duration – or more precisely, the delay imposed on searching – associated with carrying out each of these components of foraging behaviour (Goss-Custard & Rothery 1976). This allowed the amount of time per 30 s that was spent in pecking at and handling prey to be deducted from the 30 s over which intake rate was measured to estimate the amount of time actively spent searching. Dividing this amount by the time taken to make one pace estimated the number of paces made during the 30 s which, when multiplied by the average pace length of 10.3 cm, measured the linear distance searched during 30 s of foraging. Several prey and environmental variables needed to be taken into account in a multivariate analysis. Although there are no data on possible between-site differences in the sediment, the stage of the season, the tidal exposure period and the ambient temperature had all been recorded. Accordingly, multivariate statistics could be used for which, however, a data set of 15 site-based mean values was inadequate. Accordingly, the data for each site were subsetted to increase sample size. Birds had been watched in each site before site boundaries were chosen as the rate of feeding and the sizes of the consumed worms often varied between different parts of a single site. Most sites had been subdivided into two or more ‘subsites’ in an attempt to achieve uniformity in the polychaete food supply within one food patch. In addition, foraging data had been collected in most sites over several days between which the ambient temperature and tide varied. The data from the 15 sites could be used to calculate the mean values of each behaviour in 104 subsite/days of observations.

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