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Table 1 Overview of the diet of Herring Gulls breeding on Texel during the chick care of the breeding season

From: Foraging for high caloric anthropogenic prey is energetically costly

Habitat Anthropogenic Marine Intertidal Terrestrial Other-Fresh water Other-Colony
Frequency of occurrence 17.6% 33.2% 67.6% 9.9% 1.6% 8.0%
Number of samples 699 1319 2683 394 64 316
Common species/types Plastic packaging (58%) Chicken (20%) Bread (16%) Pork (11%) Flatfish (44%) Whitefish (37%) Liocarcinus holsatus (25%) Crangon crangon (20%) Small pelagics (12%) Mytilus edulis (82%) Carcinus maenas (17%) Ensis americanus (11%) Asterias rubens (5%) Insects (48%) Cattlefeed, grains (18%) Berries and seeds (17%) Earthworm (13%) Birds (13%) Rabbits & rodents (11%) Rutilus rutilus (86%) Perca fluviatilis (9%) Larus gull chicks (67%) Larus gull egg (32%)
Availability Opening hours & waste cleaning operations Nearby fishing fleets Low tide Variable Unclear Breeding season
Energetic value Up to very high ~ 10–25 kJ/g Moderate to high ~ 4–10 kJ/g Low to moderate ~ 2–5 kJ/g Variable ~ 2–9 kJ/g Moderate ~ 4–6 kJ/g Moderate ~ 4–8 kJ/g
Digestive constraint Large bones, platics, metals, glass Fish bones, scales Breaking shells with muscular gizzard Bones, fur, chitin Fish bones, scales Bones, down, eggshells
  1. Frequency of occurrence of prey types are shown per foraging habitat based on all samples gathered (n = 3969), together with the most common species or prey types within each habitat groups. Furthermore, an indication is given about the availability, energetic value in kJ g− 1 wet weight and possible digestive constraints associated with these prey. The analysis was based on regurgitates gathered in the colony during fieldwork between 2006 and 2016, see for more information references [23, 25]