Saturday, 13 January 2018

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

Tuesday, 9 January 2018

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

Monday, 25 December 2017

Between the Glühwein

Meisen Wood: various December dates.
Nets: varied between 18m and 39m.
Sound: Crested and Coal Tit (on two occasions).
Ringers: CS, EB and JL (visiting from England).

Species
Ringed
Re-trapped
Total
Blackbird
5

5
Blue Tit
10
21
31
Chaffinch
5
1
6
Coal Tit
1
13
14
Crested Tit

1
1
Dunnock

1
1
Great Tit
18
26
44
Greenfinch
1

1
Long-tailed Tit
1

1
Marsh Tit
1
4
5
Nuthatch
1
3
4
Robin
1
1
2
Total
44
71
115


The continuous dreick weather of November, the snow of December combined with family commitments in northern England and elsewhere in Germany have limited the ringing in Meisen Wood for several weeks now.  A situation deliciously compounded by visitors (including a ringer) from England, who like us, enjoyed the pleasant atmosphere of local Weihnachtsmärkte and the compulsory glugging of numerous Glühweinen along with other traditional, alcoholically laced beverages.  Between these fine indulgences a few short ringing sessions were run and the table shows the combined results.

For JL, who normally rings few passerines, the sessions were rewarding in several ways.  His joyful whoop on a net round in finding a re-trap Crested Tit was quite delightful.  He then processed the bird which was his first ringing encounter with this species.  He was pleasantly reacquainted too, on four occasions, with Marsh Tits; a species he believes he has not handled for eight or nine years.  While his comments on the weights of the Great Tits and Blue Tits are best summarised by the English idiom: little fat ________! 

Throughout the winter we record fat and muscle scores.  We find that Great Tit, Blue Tit, Greenfinch and Chaffinch pile on the fat with the fat scores rising during the day thus, late on, they are usually high up the obesity index.  Contrastingly we find Coal and Marsh Tits have low or even zero fat scores but their weights do increase during the day.  Coal and Marsh Tits caught late in the day typically being 10% heavier than those caught in the early net rounds; presumably their energy reserves are being stored elsewhere in the body e.g., the liver.  This winter fattening/weight gain is a clear physiological adaptation for the birds to survive the long winter nights and is unrelated to migration.   

Our Coal Tit numbers this year are 135% higher than previous years.  The Coal Tit (in Germany at least) is considered to be a partial migrant and irruptive consequently this would appear to be an irruptive year.  One of the re-trap Coal Tits was originally ringed in December 2015 and aged, then, as a 4.  This was the first time it has been re-caught thus making it at least three years old which is above the typical two year life expectancy for the species.

Nuthatches, according to many Belgian and Dutch studies, are strongly territorial and sedentary species exhibiting nest site and mate fidelity; with a change in mate only occurring when one of the pair dies.  Coming onto our ringing site are three territories with a fourth bordering the very south-eastern edge of Meisen Wood.  Consequently we catch few new Nuthatches and thus are wondering which of the six we regularly re-trap has possibly died?  Though given that they too have an average life expectancy of two years then ringing an occasional new nuthatch simply reflects the dynamic nature of wildlife.

Looking at Christmas and New Year family commitments, and the weather forecast this is probably about it for ringing in Meisen Wood for 2017.  So on that note:

Frohe Weihnachten und ein gutes neues Jahr euch allen!

(Happy Christmas and New Year to you all).


Tuesday, 19 December 2017

Wilstone - 17th December 2017


Weather:  calm ,cold and overcast
Nets: 280’
JT and JSJ


New
Retrap
Total
Blue Tit

1
1
Cettis Warbler

2
2
Goldcrest
1
2
3
Great Tit
2

2
Reed Bunting

1
1
Redwing
2

2




Total
5
6
11


A good deal colder than advertised but no breeze, at least to start with. This enabled us to get all three nets up at net ride one. Redwings were roosting in the bushes at the end so we disturbed them putting the nets up and only managed to catch two, the total for the morning unfortunately. Apart from two Great Tits and three Goldcrests, we also retrapped a Wilstone Reed Bunting from earlier in the year
which evidently has visited Marsworth where it has acquired the colour rings, red over red on its right leg.
We also retrapped two female Cettis Warblers ringed at Wilstone, one from the 8th of October and caught several times since. The other was first ringed in November 2013, since then she has been caught a further 5 times in the intervening years but only during the winter periods. Has she been at Wilstone all the time only visiting the netting areas during the winter to forage?
If so, she has been on her own all through the breeding seasons as no male has held a territory at Wilstone since 2011. Or is she a true winter visitor using the reed bed as a locality to survive the winter?  Is this wintering site fidelity? She needs to be recorded during the Summer to answer this, I think.

Johne


Capture dates for female Cetti's Warbler:
November 2013
March 2014
September 2014
October 2014
January 2015
January 2016
December 2017

Tuesday, 5 December 2017

Marsworth - 5th December 2017 - A high net for Redwings

Weather: calm, dull, slight mist.
Ringers LL and CMS
07:00 - 10:15
Nets: 300'
Lures: Redwing, Reed Bunting, Corn Bunting

We have not been having much success this year with the Latvian Redwing tape lure, just one bird at a time so Claire and I decided to make a more concerted effort this morning. We used one of my North Ron "thrush" nets that have a slightly bigger mesh and nice big pockets and we set it high. We used five sectional poles on each end giving us a pole length of about 4.5m (15ft). We tape the top three poles together with some duck tape for extra stability and to prevent the top pole flying off when you push the net up. The first net round gave us a Blackbird and a single Redwing but the next time round as I approached the net a huge female Sparrowhawk dived down over my shoulder into the net, it crashed around a bit and in typical fashion got out before I could get to it. She flew off and sat in the trees close by - the seven Redwings in the net were obviously interesting her!! We had to take the net down as she would definitely have come back but we were pretty happy with a tally of eight Redwings. I heard Redwings flying overhead last night so I think they are still arriving in our area and today's birds were all juvenile apart from one, whereas the birds caught up to now have been mainly adults.
Lynne


Total
New Bird
Retrap
Blackbird
1
1

Blue Tit
5
1
4
Bullfinch
1
1

Goldcrest
1

1
Great Tit
1

1
Redwing
8
8

Reed Bunting
7
4
3
Song Thrush
1
1

Total
25
16
9