Sunday, April 18, 2010

Migrants and their food sources

Female Whinchat

The last few days have seen an almost static low pressure to the west of Gibraltar, over the Atlantic. It has brought intermittent rain, sometimes heavy, and an air stream from the south. It has facilitated the migration of small trans-Saharan migrants giving them a backwind. But the cloud and rain has then forced some birds down. The numbers have not been massive but it has brought down new species for the spring, like the Whinchat (above), Orphean Warbler, Ortolan Bunting and a few others. Some of the birds that had been fattening here left us, including the male Common Redstart that I featured in earlier posts. Other redstarts took its place (below):

The beautiful Melodious Warbler also arrived this week (above and below)

As these photographs illustrate, the Giant Tangier Fennel seems to have been a favourite source of food for these migrants. We have seen how they attracted Subalpine Warblers, Willow Warblers and the resident Sardinian Warblers in earlier posts (21st March, 24th March, 6th April). It seems to be an especially important food source for Willow Warblers, now reaching their peak numbers on migration. The fennel not only provides an attraction to insects, which the warblers eat, but they also provide nectar which the warblers drink as the photographs below illustrate:

The other main food source seems to be the wild olive, now in flower and attracting many insects. It is a favourite among the Sylvia warblers but the Willow and Melodious Warblers like it too:

Whitethroat on olive

Subalpine Warbler on olive

All this commotion is watched attentively by migrant Woodchat Shrikes

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