Chapter 13 Coursework 2; the black tailed godwit

13.1 Patterns of habitat selection in breeding Black-tailed Godwits in Iceland

The black-tailed godwit is a migratory shorebird that breeds all around the lowland areas of Iceland, but little is known about its habitat preferences. The potential impact on godwits of the large-scale land drainage and increases in horse grazing that have occurred in recent decades are therefore unknown. You have data from a large-scale survey of breeding godwits, at points all around lowland Iceland, the following parameters were recorded:

  • elevation - Elevation (m above sea level)
  • swardht - Sward height (1 = 0-5 cm, 2 = 5-10 cm, 3 = 10-20 cm, 4 = 20-40 cm)
  • willows - % cover of willows, Salix spp.
  • birch - % cover of dwarf birch, Betula nana
  • juncus - % cover of Juncus arcticus
  • sand - % cover of sand and gravel
  • ditches - No. of surrounding drainage ditches (a measure of the extent of land drainage)
  • watertab - Depth of the water table (cm)
  • disthay - Distance to the nearest hayfield (m) (these are often used by feeding godwits)
  • sedpools - Number of sedge pools (pools with sedges growing in the shallows)
  • poolcov - % cover of pools within the patch
  • godoccur - godwit presence or absence (presence = 1, absence = 0)
  • goddens - density of black-tailed godwits (number/ha)

For this assignment you are asked address the following two questions as fully as possible, using the type and range of statistics that you think are appropriate and informative;

  1. Which environmental conditions influence the presence or absence of godwits?

  2. For only the sites with godwits, which environmental conditions influence godwit density?

You should then be prepared to present your findings (both results and interpretation) for each of the analyses (with professional, publication quality, figures and/or tables).

Following this presentation you will then discuss the following with your examiners;

  1. how you have tackled the data analysis for each question and why
  2. the final results for each of the analyses
  3. the interpretation of what these results indicate to you about what influences godwit distribution and density (you do not need to refer to published literature)

Presentations will be limited to 7 minutes. Discussions will be limited to 20 minutes.

You may wish to wait until after you have covered PCA and multivariate community analysis with Richard before beginning this assignment. The final workshop session of week 12 will be a help session to help you get started on the analysis for this assignment.

The data for this can be found alongside the assessment briefs on the blackboard course page under Summative Assessment > Godwit Data > assignment_godwit_data.csv. Clicking on this should download a file called assignment_godwit_data.csv.

Have a good Christmas break!