Finnish Focus on... Juvenile Caspian Gull

The season of juvenile Caspian Gull is upon us and so it's time to refresh that mental search image.

Caspian Gull (right) - Juvenile - August 18 2018. Compared with Herring Gull of the same age (left) juvenile Caspian gull are an entirely darker and more uniform beast above, whilst being a cleaner whiter creature on the head and underparts.

Mantle, scapular, wing coverts and tertials tend towards a plain, matte greyish-brown colouration (though some are warmer), with a simple, even, thin and unnotched white fringe. What notching there is, tends to be small indentations, almost like barring, rather than the large triangular sawtooth or piano key patterns of Herring Gull.

The tertials usually have a classic "thumbnail" pattern, with a plain narrow white fringe around the tip, most commonly extending just a short distance up the sides, the rest of the feather fringe being plain. As the autumn progresses on, the center of the feather tip becomes paler, broadening this fringe.

Caspian gull - Juvenile -August 14th 2019 - Some Caspian can display a more notched appearance to the upperparts feathers, however this tends to be a slightly more delicate, leafy pattern than the triangle cut of herring gull (though there is of course extreme variation and overlap in Herring too).

Caspian Gull - Juvenile - August 24th 2019 - some Caspian Gull can show a warmer, almost gingery tone to the base colour of the upperparts.

Caspian Gull - Juvenile - July 27th 2019 - fresh juvs can still appear quite dark on the head. This individual has fine notching on the coverts and tertials.

Caspian Gull - Juvenile - the rear scapulars on Caspian can often appear quite long, almost oversized, which can be further exacerbated when covering scapulars have been dropped.

Caspian Gull (center) - Juvenile - August 28th 2016 - the long rear scapulars, neatly fringed can be an excellent feature to detect birds from behind.

Caspian gull - Juvenile - August 18th 2018 - Caspian gulls fledge quite early in the summer, and so by July can appear much paler and cleaner, with a less blotchy appearance below than Herring Gull, and becoming progressively paler over the autumn.

Caspian Gull - Juvenile - August 3rd 2019 - The under wing of Caspian gull can also be very pale on juveniles, even in July.

However others can still show variable levels of fine brown barring/markings. (August 17th 2019)

Caspian Gull - Juvenile - August 17th 2019

Caspian Gull - Juvenile - August 17th 2019 - this bird is well on it's way in terms of the underwing, not yet completely white, but it's getting there.

Caspian Gull - Juvenile - August 24th 2019 - Tail pattern - the tail pattern of Caspian Gull is also variable. Often likened to the tail pattern of Rough-Legged Buzzard, with a pale rump, white upper tail and distinct black tail band, with varying degrees of barring, strongest on the inner tail feathers.

Caspian Gull - Juvenile - July 27th 2019 - Tail pattern variation

Caspian Gull - juvenile - August 14th 2019 - tail pattern variation

Caspian Gull - Juvenile - August 3rd 2019 - Tail Pattern variation - some Caspian show very little in the way of barring in the tail.

Caspian Gull (bottom) with Herring Gull (top). Compare the tail pattern of the 2 species. (August 24th 2019)

Caspian Gull - Juvenile - August 17th 2019 - the primary pattern on Caspian gull is highly variable. Normally the inner primaries are intermediate between Herring Gull and Yellow-Legged Gull in terms of paleness. However some display quite pale inner primaries, others exceptionally dark.

Caspian Gull - Juvenile - August 14th 2019 -Tail, underwing and primary pattern on display

Caspian Gull - Juvenile - July 27th 2019 - It is important to judge the inner primaries on gulls in various lights. Strong sunlight reflects heavily, backlighting can affect perception of paleness.

Caspian Gull - Juvenile - September 15th 2018 - Relatively dark inner primaries and still quite marked on the underwing and belly.

Caspian Gull (center-left) - Juvenile - August 24th 2019 - compare with juvenile Herring gulls. Note the paler head and belly, the more solid and consistent upperparts, in particular the wing coverts. The greater coverts here display dark bases, with paler tips, giving a classic wing bar effect. The innermost greater covert has already been moulted. As August progresses into September you can expect Caspian gull to be more advanced in terms of moult than Herring Gull.

Caspian Gull (rear) - Juvenile - August 24th 2019 - again compare with a variety of juvenile Herring Gulls.

Capian Gull (left) - Juvenile - September 15th 2018 - Much is made of the structure of Caspian Gull, in particular the head and bill shape, prounounced chest and long legs and wings. Here in Finland these features can be less useful than in western europe in my experieince, and is prone to variation. However, at times, you do get obvious individuals with that distinct look. This bird, with it's long, parallel sided bill, snouty looking face, high chest and long legs and wings certainly falls into that classic search image. Compare with Herring gull on the right.

Caspian Gull - Juvenile - September 15th 2018 - This individual, apart from it's classic structure, displays an interesting mix whereby some of the scapulars show a slightly leafy appearance, with others plain fringed. There are also some obvious fresh mantle/scapular feathers. The tips to the greater coverts and median coverts are paling, giving rise to the classic double wing bar we would expect by first winter, the tertials are classicly thumbnail. Compare these feather tracts with the Herring gull in shot.

Caspian Gull - Juvenile - August 14th 2019 - The "leafier" individual from above. A large bird, undoubtedly a male, This bird is also incredibly distinct structurally, with a long snouty feel to the head and face and a distinctly long bill, which though quite parallel sided, is also quite strong and heavy feeling at times. This is not necessarily unusual, especially with males.

Caspian Gull - Juvenile - August 17th 2019 - A very distinct bill structure, slim, delicate and parallel sided, with sloped forehead. Compare head structure with surrounding Herring gulls, which are more domed and rounded, as well as bill structure, with the shorter bill and more pronounced gonys on the accompanying Herring gulls.

Caspian Gull - Juvenile - August 17th 2019 - Same bird as above, in profile. A classic body structure. High chest, sleek body and long wings. Long legs and long exposed tibia.

Caspian Gull (center) - Juvenile - August 24th 2019 - again compare with acompanying Herring gulls. The bill on this individual is not particularly long, but the head shape and snout are distinctly different from Herring.

Caspian Gull (rear) - Juvenile - August 24th 2019 - Again compare with the variation in Herring gull, in particular the greater covert patterns.

Caspian Gull - Juvenile - 27th of July - do not underestimate how dark juveniles can initially appear in July.

Hopefully it won't be too long until a host of these lovely young larids pop up.

Edit 2021

Updated post with images of Juveniles from 2020 season.

Caspian Gull - Juvenile - Lohja - early August - some new scapulars coming though.

Caspian Gull - fresh bird from early August 2020 - Lohja dump - pale underwing already well progressed.

Caspian Gull - Juvenile - Late August - tail on less well marked end of the scale.

Caspian Gull - Juvenile - Late August - pale underwing.

Caspian Gull - Juvenile - Late August - Tarastenjärvi dump - new scapulars and mantle feathers well progressed. Quite open, pale greater coverts, relatively well marked median coverts. Structure very obvious. Size suggests a male. Compare with Herring Gull in background.