Pollen Encrustation on Migrant Warblers

I’ve noticed pollen encrustation around the bills of migrant warblers before – especially chiffchaffs, but this morning at Bedfont Lakes I ringed this male blackcap with the most ginormous bright yellow encrustation.

Blackcap with pollen encrustation

Blackcap with pollen encrustation

It made me wonder; where had he come from? What route had he taken to get here? What had he been feeding on to fuel him for his long journey? The majority of this species spend the winter in the Mediterranean before arriving in the UK in spring, so this sticky mass of pollen could have been collected either before it left or any where along it’s journey here. I read about a fascinating study published last year in which pollen encrustations were analysed from 4 different species of warblers, including blackcaps, upon their arrival to the UK. In doing this information about each birds recent foraging beahaviour can be collected and can give an idea as to what areas they may be using to refuel. This is fascinating stuff and the information can be used to identify stopover sites and inform conservation decisions at these sites. I like BirdGuides take on this study referring to these pollen encrustations as ‘time capsules’. There were 19 different types of pollen found – I wonder which ones this giant yellow lump contained?

The long journeys this little delicate looking feathered creatures manage to undergo never cease to amaze me, they are independent and tough beyond all expectations. They arrive here in spring, spend an exasperating amount of time and energy whilst they’re here and then come Autumn they disappear. It’s this enigmatic quality that all birds have that absolutely fascinates me. I just look at this little blackcap, seemingly tiny and delicate in my hand, and wonder ‘what life have you lived?’

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