Biometrics and movements of Redwings ringed in Grampian 1989 – 2024

(Innes Sim)

 Grampian Ringing Group ringed 701 Redwings between 1989 and 2024, and here we test if there is variation in wing length and body weight between different age classes and in different months of the year. Data on wing length and body weight were available for 6 months (Jan, Feb & Sept – Dec), but sample sizes were low in Jan, Feb and Sept (n = 14, 8 & 11 and 12, 7 & 3, respectively), so these three months were excluded from the analyses.

 Wing length

Figure 1 shows the distribution in wing length, with a mean of 119 mm and a range of 106 – 131 mm. There was no significant difference in mean wing length between the three age classes; first-year (119.1 ± 3.1 s.d., n = 438), adult (119.7 ± 3.2, n = 240), unknown age birds (119.7 ± 3.5, n = 18) (ANOVA F = 2.11, d.f. = 2, 696, P = 0.12). There was, however, a marginally significant difference in mean wing length between the 3 months: Oct (119.7 ± 3.3, n = 364), Nov (119.2 ± 3.2, n = 100), Dec (118.9 ± 3.1, n = 198) (ANOVA F = 3.40, d.f. = 2, 659, P = 0.03). Mean wing length apparently decreased during the 3 months, but the difference of 0.8 mm was small and well within the measurement accuracy and range of measurement error of different ringers (1 – 2 mm). Hence, we conclude that there was no difference in mean wing length, and thus approximate body size, in birds in different age classes or months.

These wing lengths are very similar to a larger sample from the BTO (https://www.bto.org/understanding-birds/birdfacts/redwing). Unfortunately, it is not possible to sex Redwings in the hand but it appears that males have mean wing lengths around 7 mm longer than females (males 122 mm, females 115 mm; https://www.bto.org/understanding-birds/birdfacts/redwing).

Figure 1. Histogram of wing length distribution of 699 Redwings measured in Grampian 1989 - 2024.

 

Body weight

There was no significant difference in mean body weight between age classes (ANOVA F = 2.40, d.f. = 2, 521, P = 0.09), so data from all age classes were combined. Mean body weight increased significantly between Oct and Dec; Oct (62.7, ± 5.6 s.d.), Nov (65.5 ± 5.1), Dec (72.6 ± 6.1) (ANOVA F = 158.68, d.f. = 2, 521, P < 0.001; Figure 2).

Surprisingly, we could find only one published scientific paper on Redwing biometrics in autumn, and none on how these change between months. Mean body weight of birds killed when flying into Bardsey Lighthouse, North Wales, in October 1995 was around 62 g, so very similar to our values in October (https://nsojournals.onlinelibrary.wiley.com/doi/epdf/10.1034/j.1600-048X.2000.310211.x).

 

Figure 2. Mean (± 95% C.L.) body weight of Redwings measured during October to December 1989 – 2024.

 

Why is there an increase in body weight between October and December?

First, we can rule out the possibility that birds arriving in Grampian in November and/or December are simply larger than those in October, since there was no increase in wing length during these three months. The Icelandic race (Turdus iliacus coburni) is longer-winged and presumably heavier than the nominate race (T. i. iliacus), which breeds in northern Europe (https://britishbirds.co.uk/journal/article/status-and-identification-icelandic-redwing-britain), so it seems very unlikely that an influx of Icelandic birds can account for the increase in body weight. We do, however, catch a small but unknown proportion of Icelandic birds in Grampian (Figure 3). A more likely explanation for the increase in body weight is that birds arriving in October, having just undergone a taxing migration across the North Sea from northern Europe, or the Atlantic from Iceland, are in relatively poor body condition. They then increase their body condition as they feed on invertebrates and/or berries, such that by December they have increased their body weight by around 10 g (16%) on average. The origin of autumn migrants in the UK remains obscure but it is thought that many birds subsequently move south to winter in France and Iberia, especially during winters when weather is harsh and berry crops are poor in the UK (https://www.tandfonline.com/doi/abs/10.1080/03078698.2002.9674271). An increase in body weight would allow birds to perform this extra migration leg successfully, as well as helping to cope with harsher winters for those that choose to remain in Scotland.

Figure 3. Icelandic (top) and Nominate (bottom) Redwing races trapped in Grampian in December 2024.

    

Origins of Redwings arriving in Grampian in autumn

There have been only three recoveries of birds to/from Grampian out of 701 ringed during the last 35 years! However, around 250 of these were ringed in 2024 so the recovery rate excluding these is around 1 in 150. Birds ringed in northern Norway and Fair Isle, Scotland, in October were controlled in Grampian in November, while another was shot in Portugal in December having been ringed in Grampian in October. All three were ringed as fully-grown birds and we therefore have no idea as to where their natal areas were. It seems likely that the majority of birds arriving in Grampian in autumn originate in Fennoscandia, although smaller numbers may be from in Iceland (https://migrationatlas.org/node/1782#section1). Numbers in Grampian appear to peak around November and then fall off sharply, presumably as birds make their way further south and west in search of food (especially berry) sources. It seems likely that many of these birds continue south to winter in southern France and Iberia (https://migrationatlas.org/node/1782#section1), although we currently have only a single ringing recovery to back that up.

 Next steps

We currently have a very poor understanding as to the origins of Redwings passing through in autumn and wintering in Grampian, and should attempt to increase numbers ringed by targeting favoured foraging and roosting areas. It would also be interesting to identify the proportion of birds of Icelandic origin in Grampian in autumn and winter, following the guidelines identified in a recent paper (https://britishbirds.co.uk/journal/article/status-and-identification-icelandic-redwing-britain). Perhaps through implementing these two measures we can increase our knowledge of the origins and movements of this attractive, elusive and shy, but fascinating thrush.

Winter thrush ringing in Grampian in autumn/winter 2024

 

Grampian Ringing Group has never specifically targeted the ringing of winter thrushes (Redwing and Fieldfare), and numbers ringed have usually been less than 50 per year. However, some group members put in more effort in 2022 when we ringed 61 Redwing and 36 Fieldfare. These were caught at roost sites, in gardens during snowy weather or when feeding on rowan or whitebeam berry crops. In 2023 the berry crop was very poor and there was no influx of thrushes into gardens, resulting in low numbers ringed (7 Redwing and 9 Fieldfare). However, following a bumper rowan berry crop in summer 2024 we began looking for potential catching sites with berries in the autumn. Some Redwings were ringed at Loch of Leys (26 between 11 and 28 November, including a 1^st year bird controlled after being ringed on Fair Isle on 31 October), Craiglash (59 Redwing and 7 Fieldfare between 14 November and 8 December) and Pitfichie Forest (40 in mid-November). We also located two potential ‘new’ sites, at Stewartfield, near Strachan and at Auchorrie, near Torphins. Both sites had an abundance of rowan berries when checked in October, but were not checked again until 2^nd December, by which time there were several hundred thrushes at both and most of the berries had been stripped from the trees.

Ringing site at Stewartfield:

No catches were attempted at Auchcorrie, but at Stewartfield net rides were made through dead bracken below 6 -10 m high rowan trees and we targeted those trees that still retained some berries. However, many birds were feeding on fallen berries on the ground which probably helped increase catches. We began catching on 3 December when we set 2 x 18 m ‘thrush mesh’ nets and played ‘Latvian Redwing’ song lures at both nets in an attempt to increase catches. This was pretty successful and we ringed 32 Redwing and 2 Fieldfare. We returned the following day, set 2 x 18 m thrush mesh nets again, and ringed a further 47 Redwing and 15 Fieldfare. We played the Latvian Redwing lure at one net (where all the Redwing and 2 Fieldfare were caught) and Fieldfare song at the other net (where 13 Fieldfare and no Redwing were caught). We gave the site a break on the 5th but returned on 6 December, set 3 x 18 m thrush mesh nets, played Redwing song at all 3 nets and ringed 62 Redwing. Poor weather on 7 and 8 December prevented further catches but a further 9 redwing were ringed on the 9^th in 2 x 18 m thrush mesh nets with Latvian Redwing lures, by which date there were virtually no berries left! Thus, during 4 catching days over a week we ringed 150 Redwing and 17 Fieldfare, as well as 27 Blackbird and a single Mistle Thrush.

Net ride at Stewartfield:

Two races of Redwing are recognised; the nominate Turdus iliacus iliacus breeds in northern Europe whereas T. i. coburni breeds in Iceland. The nominate race is generally lighter brown on the upper chest, nape and head and has pinkish legs, whereas the Icelandic race is darker brown on the upper chest, nape and head and has brownish legs. However, it is not considered possible to identify the race of every bird as there is overlap in feather and leg colour, and biometrics. It is currently unclear as to the breeding-season origins of birds wintering in Scotland, but it is thought that most Icelandic birds winter in the north-west of the UK whereas many birds from northern Europe winter in the south and east of the UK. We did record a few clear examples of Icelandic birds in our catches, but the difficulty in assigning birds to a specific race means that we still have much to learn about Redwing movements of both races.

Northern European Redwing race:

Icelandic Redwing race:

Fieldfare:

Mistle Thrush:

Grampian Ospreys in the Sun

 Ian Francis, Ewan Weston, Jenny Weston

Between 17 and 21 pairs of Ospreys are known to have nested in Aberdeenshire over the past eight years, though we believe pairs are missed. We know that some of our fledged youngsters are breeding elsewhere, so the movement away of potential recruits could influence our local population. In 2023, we only located 17 active nests, with pairs not present at three long standing sites and no new fully occupied nests found. There were rumours of pairs at a couple of other sites, but these were not located. Breeding productivity was a little above average though, at c.1.5 chicks fledged per occupied nest, but outcomes were uncertain from at least one site.

Six chicks were ringed in 2023 and in total, since 1993, GRG has ringed 248 Osprey chicks. Over that period, there have been 133 resightings or recoveries of at least 58 individual chicks. Most are now marked with blue plastic darvic rings with white digits (left leg) and many are now photographed or captured on nest cameras. Technology has certainly improved the reporting rate! 

An interesting set of sightings of one young bird from near Monymusk came last year, 2023. It was one of a brood of three chicks, ringed by a GRG team led by Ewan Weston on 10 July. It probably fledged around the end of July and hung around for a short while. However, from 26 August to 16 September it was near London, and was appreciated by many tens of people in that time. An easterly migration route for our birds is relatively unusual, as more often they are seen in south-west England, particularly Cornwall and Devon.

Osprey brood, Donside, 10.7.23. A chick (Blue 256) fledged from here migrated south via London, spending a week there. Photo: Ewan Weston

Osprey Blue 256, from Donside nest, Bowyers Water, Lee Valley , London 31.8.23. Photo: Stuart Fox

Another 2023 Osprey nest nearby also had a brood of three, all duly ringed. One of the chicks from here was seen by Jean-Marie Dupart on 23 January 2024 at the Karone Islands, in Casamance, Senegal (12 degrees north).  

Osprey brood, Donside, 10.7.23. A chick fledged from this nest (ring 253) was seen in Senegal in January 2024 (see below). Photo: Ewan Weston

Osprey Blue 253 photographed in Senegal by Jean-Marie Dupart on 23 January 2024.

Osprey Blue 253 photographed in Senegal by Jean-Marie Dupart on 23 January 2024

This is not the group’s first Osprey recovery from Senegal – in fact, it’s the sixth. We’ve also had recoveries from The Gambia (three), Ghana and Guinea-Bissau (one each). The sunny climes of west Africa are clearly the place to be in winter for our birds, and this is not just true of juveniles, which spend their first full year there, but also returning adults. And their predilection for winter sun also extends to many sightings in south-west Europe – either on passage or increasingly, wintering, with Portugal a popular resort and Spain a close second.

Here's another Grampian Osprey, blue JF1, also from a nest in Donside in July 2017 (another  brood of three), photographed in Senegal by Jean-Marie Dupart again, in December 2023. This bird is obviously paddling to keep cool or pretending to be a wader! 

JF1 in Senegal, Jean-Marie Dupart

JF1 is a bird with a history – it has been a regular in Cornwall on passage (seen first in the year of its birth heading south), plus near Edinburgh, and intriguingly, it was seen in summer in Aberdeenshire, so it must be a local breeder, though we don’t’ know where – somewhere on the Deveron, probably. It may well have been in Senegal every winter since then.

Sightings of Osprey JF1 since 2017:

Devoran Creek, Cornwall, 4.9.17

Devoran Quay, Cornwall 18.9.17

Tyninghame, Lothian, 15.08.19

Rothiemay, Aberdeenshire 1.6.20

Restronguet Creek, Cornwall, 9.9.2021

Restronguet Creek, Cornwall, 15.9.2022

Senegal, 9.12.2023.

Osprey chick blue JF1 in its Donside nest, July 2017. Photo: Ewan Weston

We now know quite a lot about where our Aberdeenshire ospreys go in winter and where they pass through. Although we are ringing fewer birds than previously, it is important to keep a sample going every year. Climate change may well mean that birds winter further north, and we also need to understand how our Aberdeenshire-reared birds are seeding new breeding areas further south in the UK. We would rather our local population increased, but we are also happy to see them settled further south, gradually building overall numbers – and fuelling the continued search for Osprey winter sun!

AN OLD FRIEND RETURNS

Waxwing colour-ringing this winter has been taking place in Orkney, NE Scotland and Newtown in Wales (so far up to mid-January 2024). As in previous winters there has been a single colour ring with the metal put on one leg and 2 or 3 colour rings on the other. I’m sure everybody who has seen and or photographed a colour-ringed Waxwing is happy that the bird is in no way bothered or hindered by these small and very light weight rings and is going about its activities in the very same way as all the others in the flock.

BWR stretching for a Mistletoe berry Great Malvern, Worcestershire 06/01/24, Simon Pugh

GYW drinking Hassop Station, Derbyshire 29/12/23, Simon Benyon

Metal over blue is the code for this winter 2023/24, on the right leg for Scotland and on the left leg for Wales, with the other colour rings on the opposite leg.

In case you are wondering we don’t give the birds names, just the abbreviations of their colour ring combinations!  eg BOB is Blue over Orange over Blue colour rings.

A = Ash/Grey (as G is used for Dark Green), B = Blue, G =Dark Green, L = Light Green, N = Black (Niger as B is already used for Blue), O = Orange, R = Red, White = White, Y = Yellow.

OLO Aldermaston, Berkshire 24/01/24, Dave Webster

BLB Newton Aycliffe, County Durham 16/12/23, Roger Simpson

 I think some of the observers in Colchester, Essex were quite pleased to have their colour-ringed Waxwing quaintly called BOB around, maybe not aware that it was an abbreviation of the colour ring combination until the not so quaintly named WOO (White over Orange over Orange) turned up from Stoke-on-Trent!

BOB Severalls Industrial Park, Colchester  15/12/23, John French

WOO Fenton, Stoke on Trent 09/12/23, Phil Cooper

So with lots and lots of photographs/sightings coming in during November and December showing a metal over blue ring on one of the legs it came as a bit of a surprise when an email from Alex Jones (not the one from the One Show I don’t think but I haven’t asked) came in alerting us to a post on a local WhatsApp group he’d seen with a photo of a colour-ringed Waxwing taken by Fred Fearn at Abergele, North Wales clearly showing a metal ring over a red colour ring on the right leg (and White over Red over Yellow on the left). This was the code for last winter, 2022/23, when we ringed a mere 25 Waxwings in a winter of very small numbers. I quickly got back in touch with Alex asking if there’s any way he could get in touch with Fred to, most importantly of all, get a date of when the photograph was taken to confirm it was from this winter. Fred replied himself saying it was taken on 1^st Jan 2024. What a great start to the New Year!

MR-WRY Abergele, North Wales 01/01/24, Fred Fearn 

So it was indeed a returning bird from winter 2022/23. A quick look at our ringing records showed WRY to have been ringed as a juvenile female by Innes on 30^th Nov. 2022. She was 1 of 4 birds Innes, Sam and Raymond managed to catch that morning standing with a mist net across the pavement outside a pub in Kincorth, Aberdeen. We remember laughing with a mannie that we were playing badminton! Then we were delighted to hear about her again when she rather unexpectedly headed back across the North Sea to be resighted/photographed in Denmark on 26^th Jan 2023 by Flemming Pedersen! 

MR-WRY Aalborg, Denmark 26/01/23, Flemming Pedersen

It's very exciting when we get a returning bird as we don’t get many (I think this our 8^th from around 4550 Waxwings ringed over the years by Grampian RG). Waxwings aren’t nailed on annual winter visitors like the Redwings and Fieldfares which arrive every winter from Scandinavia. Some winters can see very few if any Waxwings arrive at all, being an irruptive species dependent on the availability of berries back home.

A huge thank you to you all for reporting your colour ringed Waxwing sightings to us and kindly allowing us to use some of your super photographs on our blog. These one or two colour-ringed birds within a flock of 3 - 100 birds (or the exceptional 11 in the flock of 250+ at Hassop Station, Derbyshire!) allows us to track their movements and gives us a little insight into the vagaries of their fascinating social life, movements, fidelity and survival.

Raymond and Grampian Ringing Group

 

A MERRY WAXWING XMAS AND A HAPPY WAXWING NEW YEAR!

A Happy New Year and massive thank you to all birders, observers and photographers for reporting their colour-ringed Waxwing sightings to us. It has certainly been a busy December and start to January. See map by Euan Ferguson (below). See Sam Lopez on Twitter @Naturalist_Sam for an animated version!

It is clear from the map that many of the Waxwings moved on south out of Scotland and kept on going with several sightings south of London before the New Year. And “returning birds?!” (not on map) to Denmark, Norway and Sweden already!

                            

 RYR Farnham, Surrey 7/1/24, Emma Stephenson

                                    

 BWR Greater Malvern, Worcestershire 6/1/24, Andy Richardson

WGW Uckfield, Sussex 6/1/24, Keith DP Wilson

 YNW Barnoldswick, East Lancashire 30/11/23, Dave Markendale

However just as interesting as the movers are the stayers. Birds in the north of England included YNW, found in Barnoldswick, East Lancashire on 30^th Nov. which then turned up over a month later on 4^th. Jan only 55km to the east in Middleton Quernhow, North Yorkshire. RYW was in Gainsborough, Lincolnshire 17^th Dec. then turned up a week later on Xmas eve in Newton Aycliffe, Co Durham 145km to the north west.             

 

RYW Gainsborough,Lincolnshire 17/12/23, Joe Downing

 And a few were still hanging on in Scotland.

Lorraine McCormack photographed juvenile female WOW (below) at the south approaches to the Kincardine Bridge near Falkirk on New Years Day and also managed to capture a bit of pair bonding between WOW and an unringed male, passing a berry back and forth to each other repeatedly.

                                                

Hassop Station (Café depending on the reporters tendancies!), near Bakewell in Derbyshire was the place to be though if you’re a Waxwing with 250+ reported feeding on hawthorn berries along the old railway line. 10 colour-ringed birds have been reported from here so far between 19th Dec. and 13^th Jan. See some photos below:

 

LYW after drinking, Hassop 6/1/24, Tim Russon

 
 OGW “Where’s all the berries gone?” Hassop 6/1/24, Peter Garrity

 
WYW Hassop 13/1/24, Richard Oswold

Waxwings generally show little flock fidelity and pretty random dispersal when they arrive in the UK so it is interesting to speculate how flock faithful some of these birds at Hassop Station are. Seven have come from the same flock, same day ringing in Elgin on 13^th Nov., 1 from Aberdeen on 4^th Nov. and 1 from Orkney on 7^th Nov. We’ll take a closer look at this in a future post.

 The large flock at Hassop is feeding on hawthorn berries, a berry species they all but ignored in NE Scotland this winter, much preferring the rowan berries. It has been very interesting to see from photographs and information provided by observers what the Waxwings are feeding on at various other locations around the country.

 LLO photographed by Keith Gillon near Longniddry, East Lothian 7/1/24 was not only notable for still being in Scotland but also for feeding on rose hips.  

     

Keith commented, “The birds were managing to feed on the rose hips though they maybe did select the smaller ones.”

Interestingly WYG, seen by Angus Croudace on 27/12, also still in Scotland in Abernethy, Perthshire, was also feeding on rose hips. Rose hips are not just a Scottish thing though, Andrew Merrick reported birds at Arborfield Garrison, Berkshire feeding on them.

It was great to see the Waxwings tucking into big juicy bunches of white rowan berries at Farnham in Surrey and Orpington in Kent. This ornamental rowan, sorbus hupehensis, can be found scattered around Aberdeen but none of the trees here had anywhere near such an abundant crop of berries as those shown in the Waxwing photos from these sites.

BYR Farnham, Surrey 30/12/23, George Newton

RRB Orpington, Kent 9/1/24, R. Sim

WGW on Hawthorns Uckfield, Sussex 5/1/24, Alex Brookes 

What I’ve never seen and was reported from Great Malvern in Worcestershire and Farnham in Surrey amongst other places is Waxwings feeding on Mistletoe berries.

Mistletoe is not a common berry at all up here in NE Scotland so thanks to Emma & Graham Stephenson for some extra photographs of the birds eating Mistletoe berries in Farnham and to Simon Pugh for the video footage from Great Malvern. From what I can see the Waxwings have to work quite hard to get the berries, searching around in the foliage for each single or double berries. A big bunch of red, yellow or white berries on bare stems looks a lot easier to me but having said that the Mistletoe berries do look quite large, soft and juicy.

Waxwings feeding on Mistletoe berries Farnham, Surrey 7/1/24, Emma Stephenson

BWR swallowing a Mistletoe berry Greater Malvern, Worcestershire 6/1/24, Paul Harwood Browne

As well as reporting your colour-ring sightings (and flock size and berry types)  we would be interested to hear about any casualties anybody might have come across to add to our casualties table below.

Many thanks again for everybody’s tremendous contributions to our Waxwing tracking project so far.

Raymond and Grampian Ringing Group

 

CASUALTIES
Cause	Number
Car	2
Cat	2
Sparrowhawk	7
Window strike	20
Total	31