Larus cachinnans

(last update: February 16, 2013)

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2cy cachinnans: February

Spectrum in first-winter birds: cachinnans - hybrids - argentatus

1W birds can be scored on traits included aspects of structure, plumage and moult (table 2 illustrated HERE). When all partial trait scored as summed, individual birds can be plotted in Figure 8.

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.

1W cachinnans - Ukrain birds with sum trait scores <25 (ideally <22).

Below we present 8 cachinnans, hatchedin Ukraine outside the hybrid zone with argentatus. These 8 birds have sum trait scores from 11 to 23, and can be seen as reference and show the individual variation apparent in pure cachinnans.

2CY Caspian Gull UKK L-001754 January 13-14 2004, Lubna, Poland. Picture: Ruud Altenburg. Overall score 11, classic pure Caspian Gull.	2CY Caspian Gull PSBS February 19 2012, Zagreb, Croatia. Picture: Ruud Altenburg. Sum score 13, classic pure Caspian Gull.
2CY Caspian Gull PSSD February 19 2012, Zagreb, Croatia. Picture: Mars Muusse. Sum score 15, classic pure Caspian Gull.	2CY Caspian Gull PSVS February 17 2012, Zagreb, Croatia. Picture: Ruud Altenburg. Sum score 17, classic pure Caspian Gull.
2CY Caspian Gull PSPE February 21 2012, Bucharest, Romania. Picture: Cristian Mihai. Sum score 18, pure Caspian Gull.	1CY Caspian Gull PUSZ October 07-08 2010, Rødvig-Stevns, Denmark. Picture: Lars Krogh. Dark bird, but sum score 18, pure Caspian Gull.
2CY Caspian Gull UKK L-006330 February 19 2012, Zagreb, Croatia. Picture: Mars Muusse. Sum score 22, just within range of pure Caspian Gull without overlap of hybrids.	1CY Caspian Gull UKK L-006940 October 15 2010, Rødvig-Stevns, Denmark. Picture: Lars Krogh. Sum score 23, within range of Caspian Gull, but also overlap with hybrid zone.

1W cachinnans hybrids - Birds with sum trait scores 22-32 (ideally 25-29).

In the pictures below, some of the hybrids are birds followed in the colony, still attending parents and therefore have good papers on their identification. Other birds are "expected to be hybrids", often because some phenotypic features fall outside the limits what we currently know of pure cachinnans. Single odd features normally are no big issue and do not have severe impact on the total trait score, however, multiple odd features will raise the total score and confirm the initial idea we are dealing with a hybrid bird.

1CY hybrid Caspian Gull 21P3 August 14 2007, Oostende, Belgium. Picture: Francois Roland.	1CY backcross hybrid Caspian x Herring Gull 46P1 September 26 2006, Simrishamn, Sweden. Picture: Jörgen Bernsmo. Date of observation too early (before October), but scored anyway. Its score (25) is too high for Caspian and low for Herring and should flag it as a possible hybrid.
1CY presumed hybrid Caspian x Herring Gull 7P48 September 25 2004, Amsterdam, Netherlands. Picture: Ruud Altenburg. Parentage unknown. Date of observation too early (before October), but scored anyway. Its score (29) places this bird in the hybrid zone of the spectrum, just overlapping with lowest scores for pure argentatus.	1CY hybrid Caspian x Herring Gull PLG DN-21230 December 05 2007, Pohlsche Heide, Germany. Picture: Armin Deutsch. Mother known as Herring and father as Caspian. Its overall score was 26, outside the range of pure individuals of both species.
1CY-2CY hybrid Caspian x Herring Gull 74P1 October 2006 & March 2007, Poland & Germany. Picture: Zbigniew Kajzer & Armin Deutsch. Its score (21) places this bird within the limits of pure Caspian Gull, just outside the hybrid zone.	1CY presumed hybrid Caspian x Herring Gull PLG DN-25914 October 01 2009, Westkapelle, the Netherlands. Picture: Ies Meulmeester.
1CY presumed hybrid Caspian x Herring Gull PLG DN-25547 October 22 2009, Pohlsche Heide, Germany. Picture: Armin Deutsch. Its score (28) is too high for Caspian and low for Herring.	1CY-2CY hybrid Caspian x Herring Gull XJCWDecember 21 2011, Boulogne-sur-Mer, NW France. Picture: Jean-Michel Sauvage. Its score (28) is too high for Caspian and low for Herring.
1CY presumed hybrid Caspian x Herring Gull 42P3December 13 2007, Łubna landfill, Poland. Picture: Ruud Altenburg. Parentage unknown. Its partial score (29) places this bird in the hybrid zone of the spectrum, just overlapping with lowest scores for pure argentatus.	1CY presumed hybrid Caspian x Herring Gull PLG DN-12658 December 07 2002, Pohlsche Heide, Germany. Picture: Armin Deutsch. Partial score is 23 (no score on primary projection), which places this bird in both the high end for cachinnans but also in the lower range of the hybrid zone of the spectrum.
2CY hybrid Caspian x Herring Gull 92P1 January 19 2007, Pohlsche Heide, Germany. Picture: Armin Deutsch. Its sum score (29) places this bird in the high end of the hybrid zone, but overlapping with scores for pure argentatus.	2CY hybrid Caspian x Herring Gull 36P3 January - February 2008, Pohlsche Heide, Germany. Picture: Armin Deutsch. Its sum score (29) places this bird in the high end of the hybrid zone, but overlapping with scores for pure argentatus.
2CY hybrid Caspian x Herring Gull 846P January 17 2004, Łubna landfill, Poland. Picture: Ruud Altenburg. Parentage unknown. Its score (23) places this bird within the limits of pure Caspian Gull, but also within the range of the hybrids.	2CY hybrid Caspian x Herring Gull 748P February 17 2006, Pohlsche Heide, Germany. Picture: Armin Deutsch. This bird is very Herring-like and has a high score (30).
2CY backcross or F2 hybrid Caspian x Herring Gull 795P February 06 2006, Chioggia, Italy. Picture: Marco Basso. Father known as hybrid Caspian x Herring, mother unknown. It occupies space on the PCA biplot (fig. 9) which is distant from any Caspian Gull and outside the space occupied by Herring Gull. Its trait score is 27 - too high for Caspian and below that of any pure Herring.	2CY presumed hybrid Caspian x Herring Gull PLG DN-04520 March 10 2005, Pohlsche Heide, Germany. Picture: Armin Deutsch. Sum score (25) is too high for Caspian and low for Herring and should flag it as a possible hybrid.
2CY backcross hybrid Caspian x hybrid Caspian x Herring Gull PLG DN-19275 March 22 2006, Pohlsche Heide, Germany. Picture: Armin Deutsch. Parents known as Caspian (mother) and hybrid Caspian x Herring (father). This bird combines Caspian-like jizz and moult (note the new inner greater covert) with some plumage traits that are more like Herring or Yellow-legged Gull. Its score was 26, outside the limits of pure Caspian or Herring Gull.	2CY backcross or F2 hybrid Caspian x Herring Gull, April 19 2007, Wloclawek, Poland. Picture: Grzegorz Neubauer. Mother hybrid, father unknown. Although it is rather pale and has a slim bill, this bird is inseparable from Herring Gull; it sits in the space occupied by pure Herring Gull, with a trait score of 30.
2CY presumed hybrid Caspian x Herring Gull, April 2009, Riga, Latvia. Picture: Chris Gibbins. Ringed as a chick in a colony in eastern Lithuania where c. 50% of pairs are mixed, though its parents are uncertain. It occupies phenotypic space that fits neither pure Caspian nor pure Herring Gull and its overall trait score of 26 reflects this.

1W argentatus & argenteus - Birds with sum trait scores >29 (ideally >32).

Exaple birds, all ringed as Herring Gull pullus, either argentatus or argenteus.

2CY Herring Gull ( argentatus) CJT13 March 09 2011, Hoek van Holland, the Netherlands. Bird from Finland. Sum score (29) places this bird low in argentatus zone, with overlap with hybrids.	2CY Herring Gull ( argentatus) C59VH February 21 2010, Leiden, the Netherlands. Picture: Maarten van Kleinwee. From Finland. Sum score (29) places this bird low in argentatus zone, with overlap with hybrids.
1CY Herring Gull ( argentatus) CJP91 December 07 2010, Katwijk, the Netherlands. Picture Mars Muusse. Hatched in Finland. White-headed bird occupies space on the PCA biplot (fig. 9) just within argentatus zone (sum score 29).	2CY Herring Gull ( argentatus) ETM T-95398 January 13 2004, Lubna landfill, Poland. Picture Ruud Altenburg. Bird from Estonia. Sum score (32) places this bird in argentatus zone.
2CY Herring Gull (argentatus) JL6Z February 05 2005, S Norway. Picture Nils Helge Lorenzen. Herring Gull from Norway with sum score (30) placing this bird low in argentatus zone, with overlap with hybrids.	2CY Herring Gull (argentatus) J0AG February 05 2005, S Norway. Picture Nils Helge Lorenzen. Herring Gull from Norway with sum score (30) placing this bird low in argentatus zone, with overlap with hybrids.
2CY Herring Gull (argenteus) 5W February 28 2008, Boulogne-sur-Mer, France. Picture: J-M Sauvage. Bird from Holland, with moderately long legs (trait score 1) and a fine bill that lacks a marked gonydeal angle (score 1). Its plumage, however, is typical. Its sum score is 31, close to the average for this species (33.0) and therefore some odd structural traits do not affect its sum score markedly.	1CY Herring Gull (argenteus) PG December 09 2012, Hoek van Holland, the Netherlands. Picture: Herman Bouman. Classic Herring Gull from Holland regarding head pattern, notching on coverts and tertials, pattern of 2nd gen scapulars and bill ratio. Its overall score is 34 (or 35), higher than the average for this species (33.0), expressing the typical features for Herring Gull in this bird.
1CY Herring Gull (argentatus) J1490 November 27 2011, Boulogne-sur-Mer, NW France. Picture Jean-Michel Suavage. Hatched in Vardo, far NE Norway (70°23 N). Partial score is 32 (no scoring on scapulars, as only single scapulars are replaced).	1CY Herring Gull ( argentatus) KY14 October 19 2007, Hoek van Holland, the Netherlands. Picture: Evert Eijkelenboom. From White Sea, N Russia (67°05 N). Partial score is 28 (no scoring on primary projection & no scoring on scapulars, bird completely juvenile by mid-October).

Larus cachinnans 2CY-3CY PUEX February 2011 & February 2012, France & Germany. Picture: Alain Fossé & Armin Deutsch.

From Ukraine.