title: Terrestrial and Marine Foraging Strategies of an Opportunistic Seabird Species Breeding in the Wadden Sea.
abstract: Lesser black-backed gulls Larus fuscus are considered to be mainly pelagic. We assessed the importance of different landscape elements (open sea, tidal flats and inland) by comparing marine and terrestrial foraging behaviours in lesser black-backed gulls breeding along the coast of the southern North Sea. We attached GPS data loggers to eight incubating birds and collected information on diet and habitat use. The loggers recorded data for 10-19 days to allow flight-path reconstruction. Lesser black-backed gulls foraged in both offshore and inland areas, but rarely on tidal flats. Targets and directions were similar among all eight individuals. Foraging trips (n = 108) lasted 0.5-26.4 h (mean 8.7 h), and ranges varied from 3.0-79.9 km (mean 30.9 km). The total distance travelled per foraging trip ranged from 7.5-333.6 km (mean 97.9 km). Trips out to sea were significantly more variable in all parameters than inland trips. Presence in inland areas was closely associated with daylight, whereas trips to sea occurred at day and night, but mostly at night. The most common items in pellets were grass (48%), insects (38%), fish (28%), litter (26%) and earthworms (20%). There was a significant relationship between the carbon and nitrogen isotope signals in blood and the proportional time each individual spent foraging at sea/land. On land, gulls preferentially foraged on bare ground, with significantly higher use of potato fields and significantly less use of grassland. The flight patterns of lesser black-backed gulls at sea overlapped with fishing-vessel distribution, including small beam trawlers fishing for shrimps in coastal waters close to the colony and large beam-trawlers fishing for flatfish at greater distances. Our data show that individuals made intensive use of the anthropogenic landscape and seascape, indicating that lesser black-backed gulls are not a predominantly marine species during the incubation period.
authors.affiliation: Research & Technology Centre (FTZ), University of Kiel, Hafentörn 1, D-25761 Büsum, Germany.
authors.forename: Stefan
authors.identifier: http://orcid.org/0000-0003-0548-9346
authors.initials: S
authors.lastname: Garthe
authors.affiliation: Research & Technology Centre (FTZ), University of Kiel, Hafentörn 1, D-25761 Büsum, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Schwemmer
authors.affiliation: Institute of Marine Research (IMAR) and Marine and Environmental Sciences Centre (MARE), Department of Life Sciences, University of Coimbra, 3004-517 Coimbra, Portugal.
authors.forename: Vitor H
authors.initials: VH
authors.lastname: Paiva
authors.affiliation: Research & Technology Centre (FTZ), University of Kiel, Hafentörn 1, D-25761 Büsum, Germany.
authors.forename: Anna-Marie
authors.initials: AM
authors.lastname: Corman
authors.affiliation: Thünen-Institute of Sea Fisheries, Palmaille 9, D-22767 Hamburg, Germany.
authors.forename: Heino O
authors.initials: HO
authors.lastname: Fock
authors.affiliation: Department of Evolutionary Ecology, Leibniz Institute for Zoo and Wildlife Research, Alfred-Kowalke-Str. 17, 10315 Berlin, Germany.
authors.forename: Christian C
authors.initials: CC
authors.lastname: Voigt
authors.affiliation: Research & Technology Centre (FTZ), University of Kiel, Hafentörn 1, D-25761 Büsum, Germany.|Swedish University of Agricultural Sciences, Umeå, Sweden.
authors.forename: Sven
authors.initials: S
authors.lastname: Adler
mesh_terms: D000818:Animals; D059001:Aquatic Organisms; D001267:Atlantic Ocean; D001522:Behavior, Animal; D001717:Birds; D001947:Breeding; D017753:Ecosystem; D005060:Europe; D005398:Fisheries