Larus cachinnans
(last update:
Greg Neubauer
Marcin Przymencki
Albert de Jong
Mars Muusse
cachinnans plumages
Larus argentatus / cachinnans? 2CY 36P3 January - February 2008, Deponie Pohlsche Heide - Minden, Germany (52°23'05N, 08°46'45E).
Picture: Armin Deutsch.
Green ring from Poland. Ringed as pullus green 36P3 & metal PLG DN-21322 on May 15 2007 in the mixed colony of Wloclawek reservoir, central Poland (52°39'N, 19°08'E). No details on parentage.
This bird is very Herring-like and has a high score (29). Notched pattern on GC, transversal bars, even on very fresh lower scapulars, single rear scapulars not replaced yet, extensively streaked head, angular head shape all indications for argentatus. To discuss such birds, its good to first classify it on the 'hybrid scale' according Gibbins et al, see table below pictures.
This bird was trapped in May 2011 as breeding adult female (6CY) at the nest and re-ringed with yellow PCVU. Measurements told this to be female cachinnans. Follow link for details.
below: argentatus / cachinnans? 2CY 36P3 January 29 2008, Deponie Pohlsche Heide - Minden, Germany (52°23'05N, 08°46'45E). Picture: Armin Deutsch.
Although obviously very much argentatus, some influence of cachinnans apparent as well; like slim bill, with slight gonydeal angle and single coverts replaced on left wing.
below: argentatus / cachinnans? 2CY 36P3 February 21 2008, Deponie Pohlsche Heide - Minden, Germany (52°23'05N, 08°46'45E). Picture: Armin Deutsch.
Late February and still very streaked on head and underparts.
Below, table 2 is repeated to score this bird. The scores are in italic + bold.
Overall score is 29, which places this bird in the hybrid zone of the spectrum, but also just within the limits of pure Herring Gull (see figure 8, repeated below this table).
Table 2. Traits and scores used to characterise birds in first-winter plumage (October-March inclusive).
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| Trait | Score | Description |
| Extent of scapular moult | 0 | no first-generation feathers remaining |
| 1 | a small number (<1/3) of first-generation feathers remaining | |
| 2 | a significant number (>1/3) of first-generation feathers remaining | |
| Greater-covert pattern | 0 | simple pattern with brown centres and sharp white edges, with no white vermiculation or notching |
| 1 | white edges with delicate notches or vermiculation; or dark brown centre with white tip to 1/3 of length (i.e. white restricted to tip or distal third) | |
| 2 | clear white notches / barring creating a delicate 'piano key' pattern along the whole edge / feather; but much of feather dark | |
| 3 | lots of white (more than 1/2 of coverts looking white) distributed along the whole feather, or a bold notching ('piano key' pattern) | |
| Bill shape | 0 | Very long and slim, no visible gonydeal angle (L:D ratio >2.8) |
| 1 | Slim, slight gonydeal angle (ratio 2.4-2.79) Measured ratio = 2,77 by Mars Muusse from first picture. | |
| 2 | Intermediate (ratio 2.0-2.39) | |
| 3 | Short and deep, well marked gonys angle (ratio <2) | |
| Leg length | 0 | Long and slim looking |
| 1 | Moderately long | |
| 2 | Short or short and stocky | |
| Ventral bulge | 0 | present |
| 1 | absent | |
| Primary projection | 0 | very long (ratio >0.6) |
| 1 | moderately long (ratio 0.5-0.59) Measured ratio I/L = 0,53 by Mars Muusse from second picture. | |
| 2 | medium (ratio 0.4-0.49) | |
| 3 | short (ratio <0.4) | |
| Moult: greater coverts | 0 | all or almost all new (>75%) |
| 1 | 51-75% new | |
| 2 | 34-50% new | |
| 3 | 10-33% new | |
| 4 | one or two feathers moulted | |
| 5 | no moult | |
| Moult: median coverts | 0 | all or almost all new (>75%) |
| 1 | 51-75% new | |
| 2 | 34-50% new | |
| 3 | 10-33% new | |
| 4 | one or two feathers moulted | |
| 5 | no moult | |
| Moult: tertials | 0 | 3 or more new |
| 1 | 2 new | |
| 2 | 1 new | |
| 3 | all old | |
| Darkness of head and body | 0 | totally white |
| 1 | reduced grey wash or streaking (confined to flanks and/or single streaks around nape) | |
| 2 | light streaking/wash to head (incl. some dark around eye); isolated streaks/blotches on body. Overall, body looks more white than brown | |
| 3 | well streaked: dark mask around eye and/or streaking covering the whole head/face; body with extensive but moderately dense streaks/mottles | |
| 4 | strong and dense streaking/mottling on body and head making it appear almost wholly dark | |
| First-generation tertial pattern | 0 | diffuse white tip (like Common Gull Larus canus) |
| 1 | fine pale fringe around distal portion (like classic michahellis), possibly also with some vermiculations | |
| 2 | edges moderately notched | |
| 3 | edges strongly notched and/or some dark barring or pale patches across the feather on some or all tertials | |
| Second-generation scapular pattern | 0 | uniformly silvery-grey, darker patterning absent or very faint |
| 1 | silvery-grey background, pattern stronger than on 0, but lacks strong barring or central dark diamonds (only dark shafts and subtle anchors), with only a minority (one or two) of such feathers admixed | |
| 2 | strong, contrasting shaft-streaks, anchors and/or dark central diamonds, but these more patterned feathers are less than 1/2 of all; ground colour creamy or silvery-grey, possibly with some grey feathers mixed in | |
| 3 | strong pattern described in 2 on most (more than 1/2) of feathers, but possibly also one or two plain grey feathers or feathers with grey ground tone | |
| 4 | all feathers contrastingly patterned (with dark cross bars or diamonds), lacking plain grey feathers; feather centres buffy-brown | |
Fig. 8. Sum trait scores for first-winter Caspian Larus cachinnans and Herring Gulls L. argentatus, and hybrids. Scores are calculated by summing individual trait score values. The figure shows the percentage of individuals in the sample with a given sum value. Numbers in parentheses are the minimum and maximum values recorded.
