Larus cachinnans in the Netherlands

(last update: December 24, 2021)

Coordinators:
Albert de Jong
Leon Kelder
Roland-Jan Buijs
Merijn Loeve
Mars Muusse

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Cachinnans breeding in the Netherlands - food choice

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FOOD

Each visit we payed special attention to any food left-overs in the direct vicinity of the nest. Also, when cactching chicks, their natural reaction may be to upchuck any prey. And that's exactly what some chicks did at De Kreupel and Lelystad as well.

For season 2020, we found the following food items and prey in Lelystad colony:

  • Beatles
  • Round Goby
  • and Roach (fish species)
  • Small mammal, a rodent

Prey found around Caspian Gull nests at colony "De Kreupel" 2021.

Fish:

  • Roach
  • Roach/Rudd
  • Spike Perch
  • Rounded Goby
  • Perch
  • Eel
  • Russian Carp

Birds:

  • Cormorant eggs
  • Coot egg
  • large white-headed gull egg
  • pullus Grey-lagged Goose
  • pullus Black-headed Gull

Food choice and competition in 3 breeding gulls: Caspian Gull, Lesser Black-backed Gull and Herring Gull.

Pellets – prey type
Food left-overs around nest
Shifting resources with chick age

. Lesser black-backed gull Herring gull
. Kelderhuispolder Wormer- & Jisperveld Kelderhuispolder Vlieland
Group: n % n % n % n %
Insects 631 17.8 6 3.7 250 8.3 13 6.7
Oligochaetes 140 3.9 31 19.3 33 1.1 1 0.5
Polychaetes 511 14.4 . . 65 2.2 4 2.1
Echinoderms . . . . 19 0.6 . .
Gastropods 70 2.0 1 0.6 59 2.0 3 1.6
Bivalves 49 1.4 . . 2108 70.2 126 65.3
Cephalopods 2 0.1 . . 3 0.1 . .
Crustaceans 783 22.1 7 4.3 435 14.5 97 50.3
Fish 2812 79.3 32 19.9 650 21.6 54 28.0
Birds, non-Passerines 304 8.6 33 20.5 265 8.8 2 1.0
Birds, Passerines 17 0.5 3 1.9 29 1.0 . .
Mammals 32 0.9 72 44.7 82 2.7 2 1.0
Plants 451 12.7 4 2.5 304 10.1 5 2.6
Seaweeds 1 0.0 . . 10 0.3 1 0.5
Human waste 209 5.9 7 4.3 477 15.9 3 1.6
Miscellaneous 149 4.2 3 1.9 398 13.3 28 14.5
Sample 3546 . 161 . 3003 . 193 .
Table (link to PDF). Frequency of occurrence (n, %) of main prey types in pellets and regurgitated matter, as the most readily available and common source of dietary information in all study colonies. Under ‘fish’ both marine and freshwater types are included. Some very rare groups (hydroids, sponges, barnacles, and unidentified Nematoda) were not listed in this table.

FEEDING LOCATIONS

One of the major fish resources for breeding Caspian Gulls, both in colony De Kreupel and colony Lelystad, are the fish traps within 300 meters from teh colony.

LITERATURE

Sterfte van schubvis als discards in de grotefuikvisserij in het IJsselmeer en Markermeer
- Ir. A.B. Griffioen en dr. N.S.H. Tien -

IMARES Wageningen UR, IJmuiden, maart 2016.

De omvang van de schubvisbijvangst in het IJsselmeer wordt vervolgens geschat op een 0.3 tot ruim 15.6 miljoen vissen. Het best guess scenario komt uit op 9.0 miljoen bijgevangen schubvis. Tussen het minimum en het maximum zit een factor 50 verschil.
Welk aandeel van de commerciële bijvangst als discards overboord wordt gezet is onbekend, maar waarschijnlijk is 90-95 van de baars en snoekbaars ondermaats en dus overboord gezet als discards. (d)
Welk aandeel van de discards sterft is ook onbekend maar zal hoogstwaarschijnlijk zeer hoog zijn. In het verleden zijn proeven gedaan waaruit blijkt dat veel vissen sterven al dan niet direct of indirect (door bijvoorbeeld wonden of door een verhoogde predatiekans).

 

Diet Changes in Breeding Herring Gulls (Larus argentatus) in Witless Bay, Newfoundland and Labrador, Canada, over 40 Years
- Alexander L. Bond -
IN: Waterbirds 39 (Special Publication 1): 152-158, 2016.

The diets of gulls (Laridae) can have consequences for reproductive success, chick growth, and survival, yet there have been no quantitative assessments in eastern Newfoundland since the early 1970s. The diet of Herring Gulls (Larus argentatus) was examined through regurgitated prey items and pellets on Gull Island, Witless Bay, Newfoundland and Labrador, Canada, in 2012, and compared with similar data from 1970-1971.
There was a significant shift in Herring Gull diet composition from blue mussels (Mytilus edulis) and capelin (Mallotus villosus) in the 1970s to garbage and Common Murre (Uria aalge) eggs in 2012. Delays in capelin spawning and the large increase in breeding Common Murres on Gull Island are likely factors influencing Herring Gull diet.
Garbage, which includes human food scraps as well as plastic debris, now constitutes the single largest diet item for Herring Gulls, corresponding with a global increase in plastic pollution. The consistently low contribution of fisheries discards suggests that changes in fishing practices and availability of discards are only one possible factor in the Herring Gull decline in Witless Bay.

 

Habitat utilisation, feeding tactics and age related feeding efficiency in the Caspian Gull Larus cachinnans
- Piotr Skorka & Joanna D. Wojcik -

IN: J Ornithol (2008) 149:31–39.

The feeding behaviour of the Caspian Gull Larus cachinnans was analysed in southern Poland in 2001. During the pre-breeding period, most birds foraged on a refuse dump and some foraged in a river valley. During incubation, similar numbers of birds foraged on fishponds, gravel pits and the refuse dump. During the chick-rearing period, fishponds were the most important foraging grounds.
The foraging success of three main foraging tactics was analysed: digging on refuse, fishing and kleptoparasitism. We found that digging success was higher in juveniles than in immature or adult birds. However, older birds moved and ate more items per unit of time than juveniles, which indicates that older birds improved their energy gain simply by a higher speed of searching.
The opposite was found for fishing success. As juvenile birds made fewer attempts than immature or adult birds, fishing success was higher in adults. Adults and immature birds interrupted more attacks than juveniles, which indicates that older birds were better able to assess the probability of fish catching than juveniles. Kleptoparasitism was observed almost exclusively on the refuse dump during the pre-breeding period. Young birds kleptoparasitised more frequently than adults, but they had a lower rate of success. However, the lower success in young birds was due to victim choice, rather than differences in flight skills. Young birds kleptoparasitised Black-headed Gulls Larus ridibundus and Jackdaws Corvus monedula more frequently than adults, but none of the attacks towards these species was successful. Generally, Caspian Gulls kleptoparasitised conspecifics more often than expected from species frequency. Only attacks towards conspecifics yielded any success.

 

Reproductive parameters of Caspian Gull Larus cachinnans Pallas, 1811 in different habitats nearby and away fish ponds
- Robert GWIAZDA, Grzegorz NEUBAUER, Jacek BETLEJA, Łukasz BEDNARZ, Magdalena ZAGALSKA-NEUBAUER -

IN: Pol. J. Ecol. (2015) 63: 159–165.

Reproductive performance of gulls depends on a variety of factors, but food abundance and its availability are among the most important. Clutch and egg sizes in gulls are found to be strongly influenced by food availability, thus better reproductive performance in the colony with greater fish availability (near fish ponds) was expected in that study. We compared the reproductive traits (clutch size, volume of eggs in the full clutch, relative volume of the C-egg (the third egg in gull’s clutches) and hatching success) of Caspian Gull Larus cachinnans in five inland colonies in Poland located at a gravel pit, a lake, a river and two dam reservoirs.
Differences in the clutch size between sites were found, with the lowest at a lake. We found similar clutch volume in all studied colonies. C-eggs were slightly smaller than A- and B- eggs, in all colonies and all study years, but the relative volume of C-egg in colonies located near fish ponds (<10 km) was significantly greater compared to colonies located far away. This may be explained by high fish availability in fishponds in comparison to other habitats.
However hatching success (the ratio of the number of hatched chick to the number of eggs laid) was highest in the colony at the lake. This indicates that both inland habitats a gravel pit and a lake offered good food conditions for large gulls when fish ponds are nearby.

Bijvangsten in de fuiken-visserij op het IJsselmeer
- Willem Dekker, Leo Schaap en Jan van Willigen -

publ: DLO-Rijksinstituut voor Visserijonderzoek - November 1993

In het kader van een studie naar de effecten van de beroepsvisserij op de commercieel geëxploiteerde soorten en de overige in het ecosysteem aanwezige vis, en vogels, worden in dit rapport gegevens gepresenteerd betreffende de bijvangst in de fuiken­visserij. In de tachtiger jaren werden door het RIVO experimenteel fuiken geplaatst in het IJsselmeer, terwijl in de negentiger jaren vangsten in de fuiken van de commerciële visserij werden bemonsterd.
Analyse van de bijvangst in de fuiken-visserij levert een schatting op van ca. 2500 ton/a, waarvan in 1993 pos en bot beiden ongeveer een derde uitmaken; het overblijvende deel omvat snoekbaars, baars, spiering, blankvoorn en brasem. De bijvangst van baars en snoekbaars is in gewicht ongeveer gelijk aan de commerciële aanlandingen, in aantallen worden de aanlandingen ca. drievoudig overtroffen.
Van de overige vissoorten wordt met name in het geval van de blankvoorn, maar mogelijk ook bij de pos en bot, een aanzienlijk deel van het bestand in de fuiken gevangen. De bijvangst van baars is ongeveer gelijk aan de door predatie van vogels onttrokken hoeveelheid. De totale bijvangst is gelijk aan de voedselconsumptie van meeuwen, hoewel oorzakelijk verband niet is aangetoond.

Mammalian prey in Laridae: increased predation pressure on mammal populations expected
- Kees (C.J.) Camphuysen , Peter de Boer , Willem Bouten , Arnold Gronert & Judy Shamoun-Baranes -

IN: Lutra, 53(1), 5-20 - 2010.

The occurrence of mammalian prey in the diet of two species of large gulls, the Herring Gull (Larus argentatus) and the Lesser Black-backed Gull (Larus fuscus), was investigated in order to quantify and compare the predation on mammals in coastal and inland colony sites. Specialised coastal nesting birds and a majority of individuals in an inland colony were found to feed on mammals frequently.
The encountered mammalian prey included western hedgehogs (Erinaceus europaeus), shrews (Soricidae), voles (Cricetidae: Arvicolinae), mice (Muridae), moles (Talpa europaea), brown rats (Rattus norvegicus), rabbits (Oryctolagus cuniculus) and common brown hares (Lepus europaeus). Most mammalian prey may have been obtained on inland fields, during farming activities, some may have been captured within the colonies, and some were scavenged at roadsides.
Many coastal mainland colonies of gulls have recently collapsed as a result of persistent predation by red foxes (Vulpes vulpes). In addition, gulls breeding along the coast in the Netherlands increasingly suffer from shortages of food (mostly marine fish and intertidal invertebrates) during chick-rearing in recent years. Inland breeding became more frequent and will further increase as a result of both factors, so that the gulls are expected to increasingly include mammals in their diet.

Diet composition of the Caspian Gull (Larus cachinnans) in inland Poland:
Effects of breeding area, breeding stage and sympatric breeding with the Herring Gull (Larus argentatus)

- Robert Gwiazda, Dariusz Bukaciñski, Grzegorz Neubauer, Marcin Faber,Jacek Betleja, Magdalena Zagalska-Neubauer, Monika Bukaciñska& Przemys³aw Chylarecki -

IN: Ornis Fennica 5(2): 91-170 - January 2011.

Diet of Lesser Black-backed Gulls Larus graellsii in a Dutch inland colony
Het voedsel van de Kleine Mantelmeeuwen van het Wormer- en Jisperveld (Dutch) - January 2006
- Kees (C.J.) Camphuysen Daan C. Camphuijsen & Tom M. van Spanje -

Lesser Black-backed Gulls are coastal breeding birds that established a breeding population in The Netherlands around 1926. After a slow start the population increased markedly to around 90 000 pairs in 2002. Most breeding colonies are situated in coastal dunes and industrial estates, but in recent years, most colonies in dunes along the mainland coast have been deserted, mainly as a result of depredation by Red Fox. In search for alternative breeding sites, increasing numbers breed some distance away from the coast. The colony with c. 120 breeding pairs in 2005 at Wormer- and Jisperveld, a peat meadow area some 16 km from the North Sea coast (52°31’N, 4°50’E, 1-2 m below sea level), is an example of a recent attempt to breed further inland.
Coastal Lesser Black-backed Gulls are known to raise chicks on a marine diet dominated by fatty fish such as clupeids captured well offshore, supplemented by discards obtained at trawlers. There is insufficient knowledge of the diet of inland feeding Lesser Blackbacked Gulls, and even less of the diet of birds nesting away from the coast. We studied the diet of Lesser Black-backed Gulls in the Jisperveld colony on the basis of prey remains found alongside nests, within discrete territories.
Of 161 samples taken, 36 pellets contained just hair or grass leaves. In the remaining 125 samples, 196 individual prey items were found (1.58 per nest). Animal prey (121 samples) included fish (18.9%), mammals (34.7%), birds (23.0%), crustaceans (11.2%), insects (3.1%) and litter (9.2%; Figure 1). Insects and other soft-bodied prey were probably largely overlooked; this fraction should be assessed more accurately in later studies. Fish included both marine species (Scad, Whiting, Dab) and freshwater fish (Carp, Silver Bream, Roach, Rudd). Mammalian prey included Brown Hare, Mole, Water Vole, Common Vole, Root Vole, and Common Shrew. Bird prey included downy young of meadowbirds (Blacktailed Godwit, Common Redshank, Northern Lapwing), chicks of waterfowl (Mallard, Tufted Duck, Water Rail). Two adult Mallards and two nearly fully grown Brown Hares were probably taken while scavenging roadkills or other carcasses. All Crustaceans were Common Swimming Crabs.
In all, 15.2% of all prey were of marine origin, 9.2% were human litter, while the rest could have been picked up in the immediate vicinity of the breeding colony. Some gull pairs were specialised feeders, with one producing 55.6% of all litter prey found, two pairs producing 72.7% of the crustaceans, and two more pairs 16.2% of the fish (of which 37.5% were marine). Several of the specialist birds must have been long-distance feeders and a future study may shed light on the differences in reproductive success between longdistance prey-specialists and more opportunistic birds that feed in the vicinity of the colony.

Evaluating gull diets: a comparison of conventional methods and stable isotope analysis
- Emily L. Weiser and Abby N. Powell -

IN: J. Field Ornithol. 82(3):297–310, 2011.

Samples such as regurgitated pellets and food remains have traditionally been used in studies of bird diets, but these can produce biased estimates depending on the digestibility of different foods. Stable isotope analysis has been developed as a method for assessing bird diets that is not biased by digestibility. These two methods may provide complementary or conflicting information on diets of birds, but are rarely compared directly.
We analyzed carbon and nitrogen stable isotope ratios of feathers of Glaucous Gull (Larus hyperboreus) chicks from eight breeding colonies in northern Alaska, and used a Bayesian mixing model to generate a probability distribution for the contribution of each food group to diets. We compared these model results with probability distributions from conventional diet samples (pellets and food remains) from the same colonies and time periods. Relative to the stable isotope estimates, conventional analysis often overestimated the contributions of birds and small mammals to gull diets and often underestimated the contributions of fish and zooplankton. Both methods gave similar estimates for the contributions of scavenged caribou, miscellaneous marine foods, and garbage to diets.
Pellets and food remains therefore may be useful for assessing the importance of garbage relative to certain other foods in diets of gulls and similar birds, but are clearly inappropriate for estimating the potential impact of gulls on birds, small mammals, or fish. However, conventional samples provide more species-level information than stable isotope analysis, so a combined approach would be most useful for diet analysis and assessing a predator’s impact on particular prey groups.

Food choice. When trapped for ringing, this chick upchucked a small rodent.
Pullus Caspian Gull Larus cachinnans
F|B of "nest 002" which has 8CY PNED as one of the parents, May 16 2019, Lelystad, the Netherlands.
Food choice: a chick threw up a Round Goby (a fish species of shallow water), which is most likely 'natural prey'.
Caspian Gull Larus cachinnans
of "nest 038", with chick F|G and chick F|H May 21 2020, Lelystad, the Netherlands.
Food choice: Roach and Eel, two fish species, which are common by-catch in fish traps, therefore 'easy food' for the gulls.
Caspian Gull Larus cachinnans
of "nest C06" at De Kreupel, the Netherlands.
Food choice. When trapped for ringing, this chick threw up a melee of beatles.
Pullus Caspian Gull Larus cachinnans
F|U of "nest 029", May 21 2020, Lelystad, the Netherlands.
Food choice: pullus Black-headed Gull as prey of Caspian Gull.
Caspian Gull Larus cachinnans
of "nest M06" at De Kreupel, the Netherlands.
Fishermen empty the fish traps, which are a major food source for breeding Larus cachinnans at Lelystad.
Food resources: what do they eat and where do they feed?
Questions to better understand why Caspian Gull is doing well here.
A bird predating on a goose chick, April 23 2021, De Kreupel. Picture: Merijn Loeve.

Food resources: what do they eat and where do they feed?
Questions to better understand why Caspian Gull is doing well here.
Is kleptoparasitism on Cormorants the secret strategy? April 23 2021, De Kreupel. Picture: Merijn Loeve.