Larus cachinnans

(last update: February 16, 2013)

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cachinnans in Poland

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cachinnans rings

1cy August
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3cy January
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sub-adult January
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sub-adult May
sub-adult June
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sub-adult November
sub-adult December

adult January
adult February
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adult May
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adult July
adult August
adult September
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adult cachinnans: July

In 2006, Ronald Klein & Grzegorz Neubauer published an article in Vogelwelt about Larus cachinnans and L. michahellis. The original article (PDF) is in German, translated by Mars Muusse. "We" in the text below refers to the original authors. If any (translation) errors occur in this text, please let me know and mail to marsmuusseatgmaildotcom.

BACK TO PART 1: METHODS & RESULTS
BELOW: PART 2 OF THE PAPER

Influxes of Caspian Gulls Larus cachinnans and Yellow-legged Gulls L. michahellis into northern Central Europe – origin, causes, course and trend.

BY: R. Klein & G. Neubauer.
IN: Vogelwelt 127: 91–97.

4. Discussion

The regular occurrence of Steppe Gulls in Central and Western Europe was unknown until recently. Indeed already in the 1950s there were some Western European recoveries of birds ringed as pullus at the Black Sea coast, but these were regarded as exceptions. By that time, birds from this region were considered merely “white-headed gulls” or just a subspecies of Herring Gull, and consequently this issue received little attention. Only after systematic analysis of ring readings (Klein 1994) showed that Caspian Gull is a regular visitor on the Baltic Sea, and only after these ringed birds were used to worked out field identification criteria to distinguish it from other large gulls (Small & Gruber 1997, Jonsson 1998), there was rapid and essentially simultaneously flood of observations from most of Europe (Gruber 1996; Jonsson 1996; Garner & Quinn 1997; Groot Koerkamp & Ebels 1997; Knolle et al. 1997; Rubini 1997).

Nowadays, more observations of ringed gulls from the Ukraine are recorded in Finland (H. Koskinen, pers. comm.), Denmark (K.T. Pedersen pers. comm.), Holland (Wiegant & Steinhaus in 1997) and northern Italy (A. Talamelli pers. comm.); records published on the internet show field observations and photo’s of Caspian Gulls reaching Sicily, Norway and Ireland. It seems Caspian Gull can be considered potential visitor in most of Europe. It is worth noting that in some places in central European inland (e.g. Sachsen) concentrations of several thousand birds were registered, making Caspian Gull at certain times the most frequent local large white-headed gull (e.g. Hallfarth et al. 2005.). In a way, the spatial distribution of ring readings reflects the locations of qualified gull-enthusiasts and observers, however some facts are obvious. The following list of facts derived from a variety of (mostly non-citable) sources, primarily on internet, but also monthly, quarterly, and annual reports of various magazines like Limicola, Dutch Birding and Birding World and interviews and correspondences with gulls specialists from across Europe.
• Observations of Caspian Gulls in Germany are concentrated in the north; maximum numbers are record directly north of the Mittelgebirge. Compared to these numbers, the coastal regions are only marginally visited (pers. obs.).
• Caspian Gull regularly visits Scandinavia in late summer/fall, and can be found in the southeastern parts. The islands of Gotland, Öland, Bornholm and Mon are known to observers as so-called hot spots for cachinnans (L. Jonsson, K. T. Pedersen pers. comm.). The same applies for the Netherlands, especially the southern province near the German border.
• In Finland, Caspian Gull is relatively rare, even in southern parts of the country and despite qualified observers and an intensive "monitoring network" of local landfills; still there are few ring readings (A. Forsten pers. comm.).
• Caspian Gull seems to occur only sporadically in southern Germany, and also in Hungary it is comparatively rare (Boschert 2001; D. Gruber pers. comm.). The Danube, contrary to earlier assumptions, does not appear to function as a specific migration guideline.
• Caspian Gull is found only rarely at the North Sea. It can be found again on a more regular basis in the area of ​​the Rhine delta / Pas-de-Calais (W. Hoogedoorn pers. comm.; own observations.). Despite the high density of observers in England ring readings are rare outside Kent and East Anglia (Gibbins & Golley 2000).
• All observers agree that Caspian Gull, like Yellow-legged Gull, have a peak in late summer / autumn, at least regionally, but can also be found in any other season.

This results in the overall picture (Fig. 4) that Caspian Gulls from the Black Sea migrate westwards to Central Europe roughly along the northern edge of the Carpathian Mountains. A large proportion of birds then pass through Sachsen to the Ruhr area and some birds even further into northern France and southern England. Other birds follow a more northwest route and reach the great river valleys (Vistula, Oder) and end in the southwestern Baltic Sea.

At the moment it is just speculation how much of the population from the Black Sea follow this westwards journey, but since there are at least a few thousand birds involved performing this trip in late summer, it is certainly significant on population level. Moreover, Caspian Gull from Ukraine (Dnjepr reservoir at Kanev) only receive a metal ring (so, no easy readable colour ring) and still three to five ring codes have been recorded from almost every ring series (= 100 rings) in the research area for this publication. Metal ringed Herring Gulls from the Baltic do not show higher recovery rates for distant areas (> 100 km) (Klein 2001)! In this context it is remarkable how many ring readings were made on Caspian Gulls ringed as pullus in Odessa (approximately 1,200 birds ringed 1994-2003, T. Ardamatzkaja pers. comm.); this resulted in quite a lot of recoveries from Central Europe, but only one from Israel, although observation intensity is comparable. On the opposite, of 130 ringed juvenile Caspian Gulls in 1998 at Volga Delta (Caspian Sea), none was recorded from the West, but eleven different individuals were read in Israel (Lieber 2000; N.v. Swelm pers. comm.).

There are no ring data available to show the retreat of Caspian Gulls to the east. The increase in recovery rates in higher winter, especially in Poland, can be explained as well as an escape of bitterly cold weather in Eastern Europe. The significant decline in winter ring readings especially from inland Western Germany (Fig. 3) could be an indication of a movement back towards the east, assumed these birds do not continue their journey to Western Europe. Caspian Gull has extended its breeding area to the west in recent years and now it nests regularly in southern Poland and Lausitz. Hence, the growing number of ring readings in Western and Central Europe can not solely be explained by improved optical technology.

The influxes of Yellow-legged Gull to Western Europe in summer are well documented for some time (Bulteel 1983, de Mesel 1990). Only in the 1990s (Bengtsson 1994, Klein 1994) it became clear they also reach the Baltic Sea. Nowadays it is also known that Italian birds can reach into the Western Ukraine (K. Kravos pers. comm.). On the northern Black Sea, which actually is the breeding area for Caspian Gull, Yellow-legged Gull is often widespread in summer, including Greek ring birds that were seen here (P. Bzoma pers. comm.). One may therefore assume that the situation here is quite similar and these birds originate from the Aegean Sea and from the north coast of Anatolia. For the latter area there are no detailed studies about breeding gulls, but they “breed on rocks” and descriptions of observers (I. Weiss pers. comm.) suggest only Yellow-legged Gull is involved. When comparing the phenology, it is striking that the peak occurrence, not only for Caspian Gull but also in Yellow-legged Gull in Poland is earlier in the season than in northern Germany. This suggests that the majority of Yellow-legged Gulls do not arrive from the south, but from the southeast, avoiding the eastern Alps to use the Danube Plain and Moravian Gate to reach Central Europe (Fig. 5). This scenario is supported by ring readings: all ringed birds of this species read in Poland came from the northern Adriatic Sea. However, in West Germany ringed gulls also arrived regularly from the Camargue and Tuscany (A. Buchheim, pers. comm.).

It is also noteworthy that ring readings of Yellow-legged Gulls in Hanover start from October onwards (K. Thye pers. comm.) This could be related to a withdrawal of animals to the Mediterranean, but some birds spend winter in Hannover. However, only in the winter months significant numbers of large gulls numbers visit the local landfill, accordingly local reading activities focus on that period. In contrast to Caspian Gulls, for Yellow-legged Gull there are substantial ring readings demonstrating the rapid return to the areas of origin at the beginning of winter.

Géroudet (1992) assumed population pressure in Yellow-legged Gull to be the cause for northern migration of juveniles. On migration, young birds exploit favorable roosting areas, and once birds get older these movements become tradition for the post-breeding moult period. This explanation seems plausible for Caspian Gull too, because it is hard to imagine thousands of young birds flying into Western and Central Europe each year, without flying back again. Once the species has established post-breeding moult areas located northwest of their native colony, more and more inexperienced young birds will follow the same way, as gulls are known to be social animals. This feedback, next to westwards expanding breeding areal and population increase, is apparently a crucial factor explaining the current increasing occurrence of Caspian Gulls in summer in Central Europe.

5. Prospects

Large gulls are an illustrative example of evolution taking place in front of our eyes and right on our doorstep. Future developments are difficult to predict. Until recently, almost a third of all of southwestern Baltic Herring Gulls wintered deep in European inland (Klein 2001). But nowadays there hardly are open dumps and even the fish industry, a very important food source for large gulls (e.g. Hüppop & Wurm 2000), faces increasing restrictions ("EU quota"). Our own observations already indicate decreasing breeding success and increasing mortality in Herring Gulls from the Baltic Sea. At the same time, Caspian Gulls manage to settle new breeding sites and occur year-round in central European inland. Of all the large gulls it is obviously best adapted to exploit terrestrial food resources (Yudin & Firsova 1990). In the mixed breeding colonies along the Vistula River and in Lausitz their proportions in the colonies increase, something that is being studied currently in more detail.
The distribution of the Yellow-legged Gull in central European inland, by contrast, seems to be less progressive. After more than 20 years, there is, apart from the Upper Rhine and Switzerland, no significant increase in breeding pairs. Also, the magnitude of 1CY appearing in summer, at least on the Baltic Sea seem (own obs.), no longer reach levels found in the 1990s. Given these dynamics, it is necessary to follow further developments very closely. The current color-ring programs should definitely be continued, and every observer is hereby asked to learn more about the field characteristics of these gull species exactly familiar and please seize every opportunity to read rings or wing marks in the field. It will be exciting!

Thanks: Without the activities of the many field observers this data would not have been possible. Our special thanks to A. Buchheim (dates), P. Bzoma (Gdansk), A.
Deutsch (Bielefeld), K.J. Donner (Neubrandenburg), O. Ekelöf (Friedrichstadt), S. Fahl (Eberswalde), O. Geiter (Wilhelmshaven), A. Goedecke (Hall), T. Iciek (Kolo), A. Kormannshaus (Berlin), H. Koskinen (Nokia), G. Pellner (Eckernförde), V. Rauste (Helsinki), K. Steiof (Potsdam), K. Thye (Burgwedel) and G. Wagner (Grevesmühlen) who all did a great job in recent years and particularly kindly send us their readings. We thank Ringing centre Gdansk and Hiddensee for using the complete data sets from their area.

References

See PDF

below: large set of pictures of adult cachinnans, June 28 - July 04 2012, Baku landfill, Azerbaijan. All pictures by Chris Gibbins. Pictures from late June are, of course, in the June section.