Tuesday, 17 September 2013

Sorting out warblers

A walk around Fornebu this morning failed to turn up anything new although the Smew (lappfiskand) is still present and a couple of Water Rails (vannrikse) were calling. I was hoping for a Lapland Bunting (lappspurv) which is a shameful omission from my Akershus list but couldn’t find one. Meadow Pipits (heipiplerke) were still conspicuous although numbers have fallen from their peak two weeks ago and there was only a single Tree Pipit (trepiplerke) left and they will soon be gone for the winter. Yellow Wagtails (gulerle) are also getting scarce but there were still three feeding amongst White Wagtails (linerle) today.

Warblers are much scarce but a bit of pishing after I heard a Chiffchaff (gransanger) calling from some bushes produced 5 phylloscopus warblers immediately. It took a bit of time to work out what they all were but I came up with 3 Willow Warblers (løvsanger) and 2 Chiffchaff. These two species are very alike and I think that separating them on a quick view is not always a straightforward proposition. Some individuals require often  to see a suite of characters before making a call and even with pictures it is not entirely straightforward.
Sturcturally the two differ in wing length with Willow Warbler having longer wings presumably to aid it on its long migration that takes it over the Sahara whereas Chiffchaff winters around the Mediterranean and has shorter wings.

Willow Warbler (løvsanger). Here we can see that the primary projection is nearly as long as the tertials, i.e longer than on a Chiffchaff
Willow Warbler. Here we can see a single primary P4 is clearly the longest and makes up the wing tip

Willow Warbler

Willow Warbler - the straw coloured legs and pale ear coverts are also different to Chiffchaff. Note also a slightly stronger looking bill and paler lower mandible

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