Bahrain Bird Report

Changes in nest abundance 1994 - 2004

In 1994 I estimated the numerical size of the Socotra Cormorant breeding colony on Suwad Al Janubiyah from an oblique aerial mosaic, and arrived at a figure for the colony of 154,000 individual birds (end of season). During my Breeding Survey of Hawar in 1998 I was able to undertake a full ground survey of the breeding colony and obtain data that  enabled me to rework the 1994 results. Using a CAD software package that contained geo-referencing and morphing tools I was able to overlay my 1998 ground survey data not only over my 1994 mosaic but also over aerial photographs taken by Dr. Mike Hill in 1997. As a result I was able to calculate hard data sets for 1994, 1997, and 1998, based on the ground extent of the colony in square meters for each year. By applying nesting density data to the areas calculated, a set of comparative figures  were derived for the number of breeding pairs. Survey dates are mid November each year. The breeding season extends well into March

Density data - nests per 10m sq quadrat - are obtained by surveys of the breeding site outside the breeding season and aerial overlays

Using the same technique - ground area occupied by the colony times nesting density (a combination of ground survey using gps and aerial photography) I have been able to calculate comparable figures for the last 3 years. The steady decline from 1994 through to 2002 showed in 2003 a marked improvement, an additional 5,000 pairs + were present. It is thought that this probably represents some interchange between other colonies in the Gulf of Salwah, those on Saudi Arabian islands.