Oxwich Marsh 6 June 2021: siskins, snakes and squashbugs

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A confused weather forecast, with some websites suggesting a high chance of rain and others a dry start to the day. Thankfully the latter proved accurate, and the light north-westerly wind didn’t pick up until mid-morning. We put plenty of net through the reed bed and reed bed edge habitats, and a single net between our feeders. As is typical of early June, only the latter proved busy, albeit this will be changing very soon as we start to see youngsters of various species starting to disperse into the marsh to forage.

The catch was varied, with 102 birds of 20 species processed. A breakdown is contained in the table below:

Highlights included:

  • A control reed warbler. Information was received from the BTO within 24 hours of record submission, indicating the bird had been ringed in Dorset (as a youngster) in August 2018.
  • A good day total of six willow warblers, including females with brood patches and males with cloacal protrusions, clearly indicating breeding.
  • Our first young robin, song thrush and great tit of the year. The former two species will have had young on the wing for some time now, but it always seems to take time for them to disperse into the marsh. The great tits arrive more quickly, as they are drawn to the feeders.
  • A few relatively old birds, including a reed warbler, a great tit and blue tit all of which were initially ringed in 2017

The session was slow and steady. It was interesting to draw some comparisons between the flight feathers of an ‘adult’ (i.e. a bird in at least its third calendar year) and a second calendar year siskin, both of which were males. Photographs (taken by Amy Schwartz) are below.

Both photos show the 2nd year bird above and the the adult below.

With reference to the top photo, it can be (just about) seen that the 2nd calendar year bird had moulted all of its greater coverts and two of its tertials as part of its post juvenile moult in 2020. There was contrast between the colour / fringing of the moulted tertials and the retained tertial and secondary feathers of the second year bird. The adult male’s feathers were all of one generation and showed no colour contrast, reflecting the fact that they were all of one generation. The yellow panels in the primaries and secondaries were also a deeper colour in the adult.

The second photo indicates that the second year bird had a more pointed tail than the adult, and (again) the deeper yellow in the tail of the latter.

Recent recoveries at Oxwich / of Oxwich-ringed birds have included:

  • Two second year siskins ringed near Ilfracombe, North Devon (approximately 45 km to the south) in May 2020 and recaptured at Oxwich in May 2021. It seems likely that these have been travelling together, as they were ringed on the same day.
  • A sedge warbler ringed at Oxwich as a youngster in August 2020 and recaptured in early May 2021 at Loch Spynie, Moray, Scotland (approximately 680 km to the north).
  • A pied wagtail ringed at Oxwich in July 2019 and found dead on North Gower (Llanrhidian) in May 2021.
  • A reed bunting initially captured at Oxwich in October 2018, ring read in the field at Crymlyn Bog (east of Swansea) in April 2021.

It was the first day of 2021 on which both reptiles and insects appeared relatively abundant. The earliest risers, midges, were far less welcome than the later ones, which included a medium-sized female grass snake and common lizards under and on our reptile mats, hairy dragonflies, large red damselflies, a drinker moth caterpillar and a dock bug (a type of squashbug).

More photos, taken by Amy Schwartz and Lucy Rowley are below

Thanks to the team of Heather Coates, Val Wilson, Amy Schwartz, Dionne Jenkins, Bethan Dalton, Lucy Rowley and Tom Wright for company during a pleasant session today.

Owain Gabb

06 June 2021

Willow warbler
Our first fledgling great tit of 2021
Head of the adult male siskin referred to above
A fault bar in the tail of this whitethroat enabled it to be aged as a second calendar year bird
A grass snake under one of our reptile mats
Head of grass snake
The Squashbug Coreus marginatus, also known as the Dock Bug, is the commonest and largest species in the group that is likely to be found in the southern half of the UK.

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