Tag Archives: ageing

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A nice flock of White-winged Scoters

by Guillermo Rodríguez

Although White-winged Scoter is very common in winter along the east coast of the US and Canada, they are rarely found close enough to shore to see plumage details, or at least rarely in large numbers. In late November 2016, a huge flock of this species built up off Crane Beach, Massachusetts. The 700+ birds were feeding on an unidentified species of mollusk for a period of roughly one week, very close to shore (at least by scoter standards). The Crane Beach flock provided an exceptional opportunity to study a large number of individuals, which I couldn’t let pass. Despite the freezing ocean breeze on a very windy day, I managed to take a good number of pictures that show the variability of some key characters well.

Below I present a small sample of my pictures from that day, with the goal of revisiting and testing some of the identification and ageing criteria (presented in eg Garner et al. (2004), Reeber (2016)).

WARNING! This post contains many pictures!

All photos were taken on November 23rd, 2016, in Massachusetts. Note that due to the warm light of the sunrise most birds look very brown-tinged, but they usually look much darker in the overcast light conditions that are typical of NW Europe.

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The mollusk they were feeding on – Eastern Slippery Shell?

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White-winged Scoter: a juvenile male (right at the center) with three adult females and three adult males.

Adult males (including second-years)

Here are some pictures of adult males showing the variability of the bill pattern, the white tick mark at the eye, and the extension of brown on the flanks. As is well known, the characteristic head shape and the bill pattern allow a straightforward separation from both Stejneger’s and Velvet Scoters.

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White-winged Scoter, adult male.

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White-winged Scoter, adult male. Note the particular shape of the flank feathers.

This male (below) presents a “hint of horn”, not very different from that shown by some Stejneger’s (see, for comparison, the Stejneger’s seen in December in Alicante, Spain), and a quite equilateral nostril. The “two-stepped” head profile, lacking the oval, eider-like shape of Stejneger’s, is still very obvious.

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White-winged Scoter (left) and the recent Stejneger’s Scoter (right) from Alicante, Spain. The Stejneger’s picture © Jana Marco, one of the finders of this mega!

Some second winter individuals completely lack the white mark behind the eye, whereas in others it’s present but is still shorter than in older birds. Head and bill shape, including the markedly two-stepped profile, is usually not fully developed at this age and some still show a relatively flat head profile. Bill tip is uniformly pink, with thicker black margins than in adults. Lack of the tricolored bill pattern of adults is also typical of a young age. Some of these young adult males seem to lack the brownish feathers on the flanks, and look more uniformly black than adults.

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White-winged Scoter, second year male, lacking white tick mark.

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White-winged Scoter, second year male, with limited eye tick mark.

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White-winged Scoter, “young” adult male (presumed 2w), showing typical immature features such as greyish iris and pink bill, lacking any yellowish or orangeish tones.

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White-winged Scoter, adult male (left) and a male showing some immature traits (right), eg short eye tick mark, pink bill and not fully developed bill knob.

[Ageing female-type birds]
Ageing of female-plumaged birds is often simple, as many adult females are completely dark and even jet black. Differences in the head shape, the shape of the wing coverts (which are uniformly fresh and rounded in juveniles, and more squared in adults) and the paler belly in juveniles are also supportive. However, the most important feature for me is probably the pattern of the GCs and, in particular, the presence of white tips. The pattern is usually difficult/impossible to see when the birds are on the water, so it usually requires pictures in flight:
adult females: completely dark inner GCs, but the white tip sharply increases in size in the meadial GCs and can occupy almost the entire feather
first-year males: usually a small spot at the feather tip, of uniform size in all the Gcs or at most a gradual and slight increase, but always occupying <50% of the feather
first-year females: very small or completely absent white spot in all GCs

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White-winged Scoter, adult female: note largely white medial GCs, bright reddish feet, squared wing coverts, very broad primaries.

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White-winged Scoter, adult female.

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White-winged Scoter, first winter male: limited amount of white in the GCs

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White-winged Scoter, first winter male.

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White-winged Scoter, first winter female.

I guess ageing criteria are the same for Velvet, but I never had the chance to look into the subject in detail in Europe (Velvet is regular but scarce in Spain). I usually find it problematic to understand the pattern and variability of s1, which is sometimes described as the key feature to age these scoters, so I won’t make further comments on this feature.

Adult females

Adult females vary from very dark birds (looking like a “dirty” version of adult males) to those having the more classic brown plumage with two pale areas on the face. I think that the first type is actually much more common than the latter; the number of these overall black birds within the population appears to be only slightly lower than the number of adult males eg from a sample of 205 birds, 14.6% were adult males and 12.2% were these black presumed females. I wonder if there is an age-related variability, and the black birds are actually the older females.

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White-winged Scoter, adult female.

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White-winged Scoter, adult female: note the squarish shape of the wing coverts.

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White-winged Scoter, adult female.

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White-winged Scoter, female: dark below, slight bill bump, apparent bright feet, not very uniform back feathers… not sure about the age, could this bird be an adult?

The black-plumaged individuals are sometimes identified as first-year males with an extensive first pre-formative moult, but I think this explanation can be safely ruled out based on the GCs pattern (see the shots in flight above), the bright color of the feet, the dark irises, and the squared wing coverts shown by most of these birds. Only when the formative moult is much more advanced, around late January/February, first-winter males look similar, although with a much dirtier plumage, often looking “patchy” and not as uniformly jet black.

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White-winged Scoter, two adult females with a first-year male (right).

The head shape of these birds actually recalls that of adult males, due to a squarish head with a flat crown, a straight (non-concave) forehead profile and the hint of a bump at the bill base, leading to a two-stepped head profile, although it is much smoother than in males. Although the differences are sometimes subtle, I think these features are distinctive enough to allow separation from Velvet in most cases. Take a look at this compilation to get a sense of the variability in head and bill shape in adult females:

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White-winged Scoter, adult females: variability in head and bill shape.

Note that some adult females present some diffuse pink “brush-strokes” at the bill tip, but the iris seems to be pretty dark in all the individuals (cf first winter males, see below).

First-year males

By late November, juveniles still look very fresh, and the pale velvet at the base of the bill often looks nicely neat. Around 40-50% show what seem to be signs of moult around the face, and a few males have already developed a pale greyish iris and pink in the bill. But even birds that still have a completely juvenile appearance can be readily sexed by the elongated bill and very flat head profile, in contrast to females, which show a shorter bill and often a slightly angular (concave) head profile.

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White-winged Scoters, first-year male (left) and first winter female (right). In my opinion, many juveniles can be reliably sexed in the field on grounds of the head and bill shape. Note, on the back, another first year female (left) and first year male (right).

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White winged Scoter, first year birds. Sexing is definitely not always possible – this bird (center) looks intermediate, or perhaps on the female side?

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White-winged Scoter, first-year male: a nice bird still in completely juvenile plumage.

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White-winged Scoter, first-year male: gradual lightening of the iris, traces of moult around the face.

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White-winged Scoter, first-year male. This looks like a VERY advanced first year male.

Regarding the separation from Velvet, in addition to the head shape, the shape of the feathering at the base of the bill is quite distinctive given sufficiently close views; it extends further onto the bill than in Velvet and forms a 90-degree angle in the lower corner, always below the position of the nostril. A few more examples of (presumed) first-year males:

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White-winged Scoter, first-year males: variation in head and bill shape.

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White-winged Scoter, first-year male. Interesting individual with a narrow bill, and relatively rounded shape of the feathering at the lower corner of the bill base.

First-year females

Undoubtedly the most problematic group, many first-year females look very similar overall to Velvet Scoter. With short bills, and often concave and rounded head profiles, it may be extremely difficult to pick one out among a flock of Velvets. However, the shape of the feathering at the base of the bill, even if it is not as distinctive as it is in males, is still quite a good character when properly seen. Most birds (>60-70% ?) clearly show, below the nostril, a right angle:

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White-winged Scoter, first-year female.

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White-winged Scoter, first-year female.

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White-winged Scoter, first-year females. In a few juveniles, the pale spots merge, giving a striking appearance.

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White-winged Scoter, first-year female – convex and rounded head profile, similar to Velvet.

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White-winged Scoter, first-year female: variation in head and bill shape.

In a few birds the angle is not as sharply defined, looking rounder and closer to the nostril, and the pattern is probably consistent with Velvet. But this seems to be the exception and not the norm!

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White-winged Scoter, first-year female, showing a rounded corner of the feathering at the bill base.

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White-winged Scoter, presumed first-year female.

Steller’s Eider

One of many highlights from Gullfest 2012!

When Martin asked me to pick out a species that was a particular highlight from our recent trip to the first ever Arctic Gullfest on the Varanger Peninsula, I had to think hard. There were so many birding highlights! However there was one species that for me stood out above the rest, this was of course the iconic bird of the Varanger Fjord, the Steller’s Eider.

Steller's Eider

Steller’s Eider © Tristan Reid

I started birding at a very young age and I remember at about age eight flicking through my Birds of Britain and Europe with North Africa and the Middle East (Heinzel, Fitter & Parslow). Now there were obviously many amazing birds contained within the pages of this book, however the one that stood out to my infant imagination was the Steller’s Eider! This bird looked liked nothing I had ever seen, it almost looked like a creation of a very imaginative cartoonist. Having locked onto this species I began to read where it came from, it came from the Arctic! The Arctic was of course an exciting place for any small child to dream about, I of course day-dreamed of becoming an Arctic explorer! However in reality as I grew older and older I never had any real anticipation of actually going to the Arctic or seeing this enigmatic Steller’s Eider!

How life and expectations can change! Fast forward to April 2012. I was in the Arctic and on the Hurtigruten travelling up the mighty Varanger Fjord. Soon watching Steller’s Eider would be a reality! Some of our group located some Steller’s Eider in Kirkenes Harbour, I was secretly pleased to have missed them; after all I wanted to locate my own! As we passed the epic  Hornøya Bird Cliff and moved towards Vardø my eyes focused on a group of four small ducks flying in the wake of the boat. The distinctively striking plumage of the drake made these ducks instantly recognisable. BOOM I had seen my first ever Steller’s Eider! I was in the Arctic AND I had seen Steller’s Eider, this was nothing short of emotional!

Steller’s Eider and Common Eider

When we settled into our hotel rooms (Vardø Hotel ) I was astounded to see that I could see Steller’s Eider from my room! Every morning when I woke up I looked out the window and got my early morning fix of the iconic species!

Once the excitement of seeing my first ones had slightly (only slightly) calmed, there was ample opportunity to actually watch these birds in detail. Vincent van der Spek pointed out a very nice feature shown on the drakes; the isolated black spot on the side of the breast is a unique shape on each individual bird, sort of a Steller’s Eider fingerprint! Whilst watching a group of Steller’s Eider;  Martin Garner and Nils van Duivendijk indicated to me how to age the females. Once I got my eye in, this was fairly straight forward; the key was the speculum, lacking the bright colouration in immatures.

Steller’s Eider flock (including a few 2nd cy birds) © Tristan Reid

Some of the immature drakes were fairly obvious showing the progression from brown duck  into the white plumage of an adult. However Martin & Nils pointed out that there were a proportion of drakes that were still predominantly brown only separable from the females by their head shape and the tone of their tertials. Is there more to ageing Steller’s Eiders yet to be discovered?

Steller’s Eiders © Tristan Reid

So my experience of seeing my first Steller’s Eider was not only superficial excitement of the realisation of a childhood dream, but it had great depth and was also a fascinating learning experience! You’ve got to love Varanger 🙂