A
still but overcast morning with rain forecast to come in late morning, and a
small team left us putting up less net than usual, restricting ourselves to 400
feet in the reed bed and 60 foot in the scrub near the feeders.  A
northerly breeze stiffened through the morning, and nets were down by
11:00am.  With rain falling on the drive out of Gower, we’d made the right
decision.

Grasshopper warbler

We
opened the reed bed nets to the sound of a Grasshopper Warbler reeling close
by, so it was of no surprise that the first bird extracted was a retrap,
perhaps proving this species is again breeding in the Marsh.

The
features of the catch were the high proportion of juveniles of most species
processed during the morning.  This included the first young Cetti’s
Warbler of the year.  Cetti’s is a species we hear regularly with its
characteristic song burst while skulking in the scrub and reeds around the
Marsh, and it’s rewarding to once more prove breeding.  Juvenile finches
were ever present at each net round, with a good number of young Chaffinches of
note.  Of the Great Tits trapped, only one was an adult.

Of
the juveniles caught, most were coded as 3JJ indicating that they were yet to
commence their post-juvenile moult.  In contrast, two adult Willow
Warblers processed at the same time showed differing moult scores, looking very
different in appearance in the hand.  One was yet to commence moult having
severely abraded primaries.  The second bird was in main moult, replacing
flight and body feathers.  Willow Warbler is the only British species that
undertakes a full moult twice a year. Adults moult soon after breeding, with
the new feathers grown not being of very high quality and adults and
first-years undergo a complete moult in Africa. This ‘winter’ moult occurs just
before the birds start spring migration north.

Willow warbler

Both
our birds were dark-legged and not especially green or yellow in
appearance.  Wing formulae and supercilium length aided identification,
but highlights the need for caution when attempting to separate Willow Warbler
and Chiffchaff in the field without any auditory or behavioural cues to help.

The
retrapped Blackcap was a male and aged as code 5, i.e. a bird hatched in
2015.  It had a black cap, one retained old greater covert and worn and
pointed tail feathers, yet to be replaced.

A
rewarding session, with a good total considering the nets erected and duration. 

Thanks to Darren Hicks for keeping the feeders stocked during the week.

Wayne Morris

26 June 2016