Monday, May 11, 2009

Reservoir blogs - Walthamstow

Yesterday I visited Walthamstow Reservoirs in London (Canary Wharf towers just visible in the photo below) for more sound recording. Of most interest was a male Cuckoo uttering the familiar sound of spring. At the end of one bout of singing, a female gave the less often heard rippling or bubbling call (see first sonogram below) and the male immediately flew off in pursuit of it as it flew across one of the large water-filled basins to a wooded island. There are a number of possible hosts in this area though Reed Warbler or Dunnock could be the most likely. Also below are sonograms showing the trilling territorial voice of the Little Grebe (a chattering Reed Warbler also present on the recording) and some high-pitched social screams from a Swift.


Warren Baker said...

Those sonagrams are fascinating Fraser. I think we all hear something different!

Greg Morgan said...

Hi Fraser
I was at Walthamstow reservoirs yesterday morning (enjoying the glorious spring sunshine!), and saw what I believe was a female rufous cuckoo. Not being a bird watcher, at first I thought it was a bird of prey (reddish brown in colour, about the size of a pigeon), but seeing no other birds paid much attention I realised probably not. She was about 40m or so away, flying from one tree to another on one of the islands, so it was a brief glimpse. I'd been watching reed warblers on the edge of the lake, and would occasionally hear a gurgling/gargling sound from within the reeds at very close range. My powers of deduction (and I may have got this totally wrong!), having read your blog, lead me to suspect the warblers may be raising a female cuckoo chick - hence the peculiar noise.

I'd be very interested to hear your thoughts.



Fraser Simpson said...

Yes, there has been at least one rufous female around. The most likely reason that they morphologically mimic Sparrowhawks is that this allows them to scare potential hosts away from the nest. Cuckoo researcher, Nick Davies at Cambridge has carried out various experiments with stuffed models and discovered that the heavily barred underparts are the cue. Worth another trip soon to look for Cuckoo fledglings.