ASSESSMENT OF BIRD PREY AVAILABILITY – CHICHESTER HARBOUR (2013)

Client: Natural England

BUG was commissioned by Natural England to undertake a survey of intertidal invertebrates in Chichester Harbour. The principle aim of this project was to compare bird feeding resources available at the commencement of the waterfowl overwintering season in September 2013 with a mid-winter assessment previously determined in December 2012-January 2013.

The specific objectives of the study were to:

  • Compare distribution and abundance of invertebrates with the results from the 2012-13 study
  • Compare presence of algal mats with those from same sites sampled in 2012-13
  • Compare bird densities with invertebrate biomass

Hand core and box core samples, deployed from a survey vessel, were collected at each location. In addition, macro-algae biomass was determined from box quadrat samples, particle size distribution was obtained for hand core samples and 1 m2 quadrats were visually inspected for other fauna. All data were analysed and plotted with GIS.

Overall, invertebrate community structure was broadly similar within the sites surveyed. Invertebrate biomass was much greater in September 2013 than in the previous winter; however, this was largely attributed to very high densities of the gastropod Peringia ulvae.

Numbers of birds that are known to feed on Peringia (e.g. dunlin, shelduck and knot) have increased in recent years. In contrast, densities of polychaete worms were low, with subsequent influences on the abundance of birds that prey on these organisms.

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