Meisen Wood - Phew!

Date: 14 - 1 - 2018

Nets: 63m (winter configuration)

Sound: none

Weather: cold becoming warm later

Ringers: CS and EB

Species	Ringed	Re-trapped	Total
Blackbird	3		3
Blue Tit	24	14	38
Brambling	3		3
Bullfinch	1		1
Chaffinch	3	1	4
Coal Tit	3	5	8
Crested Tit	1	1	1
Dunnock		1	1
Great Tit	22	23	45
Greenfinch	13	1	14
Long tailed Tit		5	5
Marsh Tit	3	7	10
Robin		1	1
Wren		1	1
Total	76	60	136

Phew!  What an active and thoroughly rewarding session.

A near freezing start with the cold metal, sectional net poles rapidly chilling our fingers was a temporary discomfort as an abundance of birds kept us busy for the whole session.  Indeed the final tally of 136 birds would have been higher but we closed a couple of the nets, twice, so we could comfortably and safely extract, and process the birds.

Meisen Wood is not idly named: with 80% of today’s captures being tits; and 61% being Great and Blue Tits.  The recent influx of tits (and finches) is undoubtedly due to the feeders.  With 53 new ringed tits today the question is where have they come from?  This simple question demonstrates that we still have plenty to learn about the movements of “common and local” birds.

Similarly intriguing is the age profile of the Great and Blue Tits.  Last autumn we lamented the low numbers of these species and particularly the near absence of juveniles.  Then we partially explained this as a consequence of two consecutively poor breeding seasons.  This conclusion was based on our nest box monitoring results in the last two years, when many broods were unsuccessful. Today’s session, for both species, gave ratios of 3:1, juveniles to adults (same results apply to last week’s results too); these figures were first captures on the day, same day re-captures were not included to avoid skewing the data.  So clearly both species have bred relatively well – somewhere, but not in the vicinity of Meisen Wood.

We both like Blue Tits not just for their striking colourful plumage but their feistiness too.  In extracting Blue Tits, often an involved process as they can become quite entangled, we admire how a 10g bird will take on a 90kg man by frenziedly pecking the extractor’s fingers.  Though this is a non-contest, the pecks are not particularly painful (though after extracting several hundred in a day the pecks can be), they are a sharp reminder of the organism’s determination to survive as we will be perceived as predators.

When we are busy processing birds we do take moments to appreciate their intrinsic beauty.  Today this particularly applied to the Bullfinch and the Bramblings.  The exotic colours of a male Bullfinch give it an almost tropical demeanour; while the complex assortment of the Brambling’s blacks, browns, yellows, oranges, whites and greys are simply wonderful, they are also useful in sexing and aging this species too.

During the morning we had enjoyed the sight and sound of several White fronted Geese skeins flying over.  These were probably “local” birds that have, at least temporarily, halted their migration because of the unusually mild weather.  They were simply moving between feeding areas.  Then while we were packing up we were treated to a flock of bugling Cranes flying over, going to the south-west; normally by now these birds are in Spain.  With a snowy forecast for the week ahead we may wish we were southern Spain.   

Brambling

Bullfinch

Wilstone Reservoir - 7th January 2018

As I drove down through the settling snow on Sunday I naturally thought what the..... and why didnt I go on Saturday,at least the forecast had said light winds and only a chance of light rain.

However since Jenny had arrived and we were expecting guests from Amersham we carried on putting net ride one up as the flurries of snow receded and the Green Sandpipers were calling. No luck on that front; too windy out at the end of the stream.

Emily and Sandra arrived along with our guests and strangely despite everything so did some birds. A male Fieldfare obligingly flew into net one as we stood close by. Later Redwings and Blackbirds, two Redpolls and a Chiffchaff made for a very pleasant morning indeed.

Johne

	New	Retrap	Total
Blabi	2	1	3
Blue Tit	1		1
Chiffchaff	1		1
Dunnock		1	1
Fieldfare	1		1
Goldcrest		2	2
Lesser Redpoll	2		2
Long Tailed Tit		2	2
Redwing	4		4
Total	11	6	17

Meisen Wood - Gold Reflections

Where are they?

Are they coming?

Why are there so few of them?

There numbers are so low!

What’s happened to them?

These thoughts, pertaining to Goldcrests, pre-occupied much of our ringing last autumn.  The Goldcrest is the species we have most ringed in Meisen Wood with an annual average of 556 birds.  This average would have been substantially higher if in 2015, and 2016, we had not committed the ringer’s heinous crime of running out of rings.

In partial mitigation, we would plead that on realising that this was going to happen we telephoned the Heligoland Offices in Wilhelmshaven and placed an emergency order for additional rings.  And the lady at Heligoland HQ, who is responsible for ring distribution, efficiently dispatched them immediately for overnight delivery; as evidenced by the packages’ postmarks.  Lamentably Deutsch Post were thoroughly inefficient taking nine, and ten days, respectively to deliver the rings; by which time the Goldcrest passage had finished.

Thus in anticipation of the 2017 Goldcrest migration I ordered an additional 1200 Vrings (the equivalent to the BTO’s AA rings).  Part of the anticipatory excitement was the thought of collecting more measurements to statistically strengthen the data set for our own studies on this beautiful, diminutive bird.  Additionally, we had conducted a good deal of preliminary work to gather data to test a couple of hypotheses we have about Goldcrest passage along the Teutonburg Hills.

Oh my; the best laid plans!

Our final figure was a 114 Goldcrests caught and processed; this is an 80% decrease in numbers.  This disturbing numerical decline is compounded by an examination of the age profile of the captured birds.  In previous years the adult to juvenile ratios were in the order of 1:5; last autumn the ratio was 1.5:1.  For such a short lived bird this, if repeated across its European range, will mean recruitment into next years breeding population will be severely compromised and so inhibit population recovery.

So yes, this data maybe depressing but it is invaluable! The data indicates that a population event has occurred; this is part of the fundamental value of standardised and consistent bird ringing.

A fascinating aside is that an interesting migration pattern between UK Goldcrests and German Goldcrests exists.  Many UK Goldcrests in the autumn migrate to the near continent: Belgium, France, Germany and the Netherlands.  Simultaneously, going in the opposite direction, are Goldcrests from the near continent’s breeding population.  Then in spring these movements are reversed; an intriguing cross-over.

The Goldcrests passing through Germany naturally include some of the German breeding population but many more originate from Fenno – Scandinavia; for instance we have controlled Goldcrests from the Russian Baltic enclave around Kaliningrad (a straight line distance of 925km).  Baltic State bird observatories ringed low numbers of Goldcrests last autumn but, unfortunately, year on year comparative figures are currently unavailable. Though Falsterbo, the Swedish Bird Observatory, in its preliminary analysis of its autumn 2017 ringing results report a 58% decline in Goldcrest numbers.

So back to the original questions and thoughts – why such a decline?  Several possibilities exist.  Firstly the Goldcrests could have had a disastrous breeding season in Fenno-Scandinavia.  Such poor productivity could be a consequence of poor weather; inadequate food availability; or high predation rates.  Secondly Goldcrests are typically double brooded (an amazing energetic cost for such a tiny bird), perhaps local conditions, this year, limited brood size and breeding attempts. Thirdly, did poor weather effect their migration?  Alternatively, does the Goldcrest population periodically fluctuate, like that of many small mammals, with regular peaks and troughs?  And this was a trough year.  An intriguing part of biological studies, to which ringing contributes, is that answers are rarely the result of a single factor. 

With over a thousand V rings we are definitely prepared to monitor next autumn’s Goldcrest passage. Thus we are looking forward to ringing more Goldcrests, and increasing our data set to gain further insights into Goldcrest migration through this area of Germany