Monday, 15 July 2013

Night creatures

Over the past few weeks Paddy Jenks and I have been spending far too many nights crawling through dense, midge infested, conifers in a desperate search for Nightjar nests. The purpose of all this night-crawling is to investigate the size and productivity of a population of Nightjars at a consented wind-farm site in southwest Wales both pre-construction and during operation. Nightjar nests is this habitat are nigh-on impossible to find by cold-searching as many of them are located in small clearings in near impenetrable thicket stage sitka spruce. Hence we have been using small tail-mounted radio-transmitters to help us locate sitting adults. Males are fairly easy to catch using mist-nets and tape-lures of the male's song but are not that easy to track to nests as they only spend brief periods incubating whilst the female is off feeding. In addition, up to about one quarter of all males may be un-paired. Females are dead easy to track to nests but in typical sod's law fashion they generally do not respond to tape lures and so are much harder to catch. So far we have managed to catch 5 males (three of which are re-traps from 2012) and 3 females (all new birds) from an estimated population of approx. 12 churring males.

Measuring the wing on a female Nightjar. The similarity to Swift is striking and a clear example of convergent evolution

Females lack the white wing and tail spots of the adult male

"What big eyes you have" A female Nightjar takes a breather on my wing mirror whilst adjusting it's eyes to the outside light levels.

 Yesterday was a real red-letter day as we located 3 more nests doubling the total so far this year to six.

This nest was in a small clearing in 30ft high thicket stage spruce!

This one wasn't!!

One nest has already been predated on eggs but three birds are now sitting on two eggs each and the two others have produced 3 chicks between them which have already been ringed and are now near fledging.

Two is the normal brood size for Nightjars with one chick hatching about 36 hours after the other. The eldest of these two is about 5 days old

Perfect age for ringing and not far off fledging! Nightjar chicks, like ground-nesting game birds, can fly at a very early stage. Fortunately, addled eggs aren't that common

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