• Vincent

Two new articles are added to the site!

Citrine Wagtail ID: do flight calls tell us which subspecies is involved?

Could calls shed some light on the subspecies that reach NW Europe as vagrants? Maarten Wielstra collected a team of people to work on an analyses to find out if the calls of various ssp. differ on their breeding grounds. See more here.

Hybrid redstarts in Europe and North Africa: an analyses of 121 hybrids

Nicolas Martinez, Bern Nicolai and I wrote a British Birds paper on redstart hybrids. A summary of the analyses can be found here.

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  • Vincent

The 2018 ringing report for Meijendel, Wassenaar is out now!

Download here (pdf; 4 MB; in Dutch only)

English summary

When the first day of a year sees the highest number of birds ever trapped for a snowless winter's day (exactly 100), and one of these birds is a new species for the site (Coues's Arctic Redpoll), than that's nothing short of an amazing start. Partly due to two late cold spells in March our ringing group Vrs Meijendel, situated in the dunes of Meijendel, Wassenaar in the western part of the Netherlands equalled or even broke the records of four species (in terms of number of birds ringed) even before the start of the breeding season. As always we participated in the European Constant Effort Site project (CES; for breeding passerines) from mid-April to the end of July. In terms of (re)trapped adults and young birds ringed, CES was fairly good this year. Though the country witnessed the most severe drought in >40 years, the ongoing summer weather did result in a lot of suitable days for trapping. For the first time in many years, there was fairly good dispersion of immature Nightingales (total number for 2018: 129). The weather in autumn was variable, but there were still plenty of opportunities to go out ringing. The good numbers of Common Redstart (88), Cetti's Warbler (8) and Yellow-browed Warbler (17) brought colour to our autumn, and the Goldcrests arrived remarkably late, but otherwise autumn was fairly predictable: there were no serious invasions, falls, or remarkable species, though we did trap what was only our second Tawny Owl for the site in 56 years of ringing (despite their year-round presence in the area). Surprisingly a Barred Warbler trapped on 17 September was re-trapped on 20 October (34 days later) and then on 4 November (49 days). On all dates it was in good health. Though seen in the field before it was trapped on the first date, there was no sign of the bird between the catches. Not only is November very late for this species, a minimum stay of 49 days is (by far) a Dutch record. In November we assisted in an international pilot study on Starlings, that focusses on the orientation of these birds during migration. We will stay involved for the next few years. During the same month we finished the field work for our ten year genetic study on Chiffchaffs: we collected our final feather samples. Currently we are working on the first series of manuscripts. The year ended remarkably similar to how it started: again there was some movement of Redpolls and, amazingly, they were joined by a second adult male Coues's Arctic Redpoll. During the year we received multiple guests, guided several excursions, gave lectures, spoke to the media on a few occasions and published several papers. In 2018 the 17 people in our ringing group trapped birds on 100 days (a record for this century), during all months of the year. In all we ringed 6.068 birds and we re-trapped another 710 (11,7%), divided over 82 taxa (average 2008-2017: 78). Ten species were more common than ever, and another two species equalled their record year. On the other hand, some species we normally ring (nearly) every year, were absent. Surprisingly not a single Magpie, Savi's Warbler and, for the first time this century, Bullfinch were ringed. Outside Meijendel we ringed another 373 birds of 12 species (mainly chicks). Three of these species were not also ringed in Meijendel, so in 2018 we ringed a grand total of 6.459 birds of 85 taxa.

Here are some images that did not make the year report:

No, this is not a moth, it's a Wryneck's tail! With five birds ringed it was a fairly good year for them.

Male flava Yellow Wagtail: four birds ringed meant a record number for our site.

Both Dunlin and Ringed Plover are normally scarce around our ringing site, but during a cold spell in March good numbers were trapped: 30 Dunlins - including a Polish ringed bird - meant a record number, and the 5 Ringed Plovers equalled their best year.

The same applies for Eurasian Curlews. These photographs were taken on the small grassland on our ringing site.

With 88 Common Redstarts trapped, we nearly doubled our previous record (49). This stunner here is an adult male.

15 years ago we wondered if we were going to trap a Yellow-browed Warbler that year. Now we wonder how many! We even missed a series of very suitable days this year, but 8 on a single early October day was impressive, and a total of 17 ringed equalled our best year so far.

Adult (left) and 1st cy Spotted Crake.

Since this was the last year we collected Chiffchaff feathers for DNA-analyses, this Siberian Chiffchaff is a good species to end this short photo series with. Back in 2008, we were the first ringing site that started collecting feathers. Ten years on this is the most satisfying ringing project I've ever worked on. Boy, did we learn a lot! We are currently working on the first paper. Many thanks to Peter de Knijff for his analyses. On this website I'll keep on stalking you with these little gems!


  • Vincent

In many respects autumn was remarkably slow. But November turned everything upside down!

Like in spring (with an Alpine Swift), the girls from De Wulp delivered the highlight of the season (year!).

On 5 November Lizzy sent me a WhatsApp message. She asked if I knew which species was just taken into care. Despite the pics showed a wet and scruffy bird, my pulse raised and I missed a heartbeat or two. Even I was left speechless for a bit. This was an American Catharus thrush!

A new pic of a dry bird confirmed it was a Grey-cheeked Thrush (or a theoretical Bicknell’s). A new species for the Netherlands!

Despite it was in a rather poor condition, birds are in good hands at De Wulp: it recovered well. In all I saw the bird four times. They are tiny for a thrush! The size of a Common Nightingale, but with remarkably longer wings (no less than 2cm longer). On 20 November I released the now fully recovered bird at a suitable site near where it was found. It immediately disappeared into the thickets, never to be seen again.

So how did I rule out the very similar Bicknell’s? And how did I age it?

Plumage features overlap, but Bicknell’s - a split from Grey-cheeked - e.g. has a slightly more rufous tail. The cheeks should be plain. Bicknell’s is said to have more yellow on the lower mandible – which could fit this bird. However, David Sibley questions this feature. In this bird the cheek is striped, and the tail is not slightly rufous. It has the same colour as the upperparts. So that's reason nr 1) to think about Grey-cheeked rather than Bicknell’s.

The key features, however, are in the wing structure.

First of all there’s the wing chord. I measured 102 mm. Based on other sources, Rimmer et al (2001) mention:

"Wing chord of adult Bicknell's 82-100 mm (n = 415; VINS), of Gray-cheeked 93-109 mm (n = 200; Pyle 1997)."


"Majority of Gray-cheeked Thrushes have wings >95 mm in length (Ouellet 1993); 85% of Bicknell's have wings <95 mm (VINS)."

So 2) the wing chord seems to diagnostically rule out Bicknell's.

But there's more.

The longest primary is p3 (counted from outside in). In Bicknell’s this should be P4.

Finally I measured the primary projection with a ruler. In general this is ≥ 100% in Grey-cheeked and ≤ 100% in Bicknell’s. In this bird I measured c 115% (yes, they have extremely long wings). That’s even larger than the extreme for Bicknell’s (110; Lane & Jaramillo 2000).

Based on this (not ideal) pic I measure a primary projection of 111%. With a ruler I measured 115%.

So 3) the wing diagnostically confirms the ID

Ageing this bird is straight forward.

There’s more to it, but note all greater coverts are still juvenile, with a pale tip (in this species it seems to be normal that no coverts have been moulted). In adults these are plain.

Just note the funky little detail on the inner three coverts, that have a beautiful white shaft streak!

Happy Rinse, Gerjon and myself seconds before the release, Den Haag, 20 November 2018 (pic: Roland Wantia).

PS With the Alpine Swift Rinse and I added two new species to the list of birds ringed in the Netherlands in a single year. All thanks to De Wulp!

#GreycheekedThrush #GraycheekedThrush #ageing #identification

Little Bunting
The most interesting thing about this chapter is the sexing of birds. This could be done on the basis of lateral crown stripe: a new feature for me. Because of overlap between adult females and young males, birds should first be aged. The authors emphasize that this is their vision, and not necessarily the final answer to this matter. I found one in the field in October (Figure 4-5) of which I took reasonable pictures. The very rounded tail feathers look adult, as do the tertials and large coverts. The lateral crown stripe appears to be jet black and is separated from other feathers, such as the greyer back of the head. The orange-red crown stripe really stands out. Conclusion: according to this book this must be an adult male! The deep brown-red cheek - a variable feature according to this book - also fits that. So it works then? Well… how useful this really is, remains the question: based on this book I would label two "females" in Shirihai & Svensson (p546 both top right and bottom right) as males! The caption of one of these even mentions "safely identified as a female" because it has a relatively dull plumage for an adult bird. But is also has a jet black, strongly separated lateral crown stripe! The bird at the bottom right even has a pretty deeply coloured cheek, which I would be happy to call a male. Is this due to different insights, and if so, who should I believe? Or am I not interpreting this correctly? In any case, it is fascinating!

© 2018 by Vincent van der Spek