1 June 2004 Foraging Patterns of Breeding Olrog’s Gull at Golfo San Jorge, Argentina
Pablo Yorio, Flavio Quintana, Alejandro Gatto, Nora Lisnizer, Nicolás Suárez
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The spatial distribution and use of feeding areas by Olrog’s Gull (Larus atlanticus) breeding within a 34 km2 inlet at Golfo San Jorge, Argentina was investigated. Radio-transmitters were deployed on eight breeding adult birds during the late incubation period in 2001. Feeding areas were identified by means of radio-telemetry on the basis of 93 bird locations during a total of 89 foraging trips, and by direct observation of instrumented birds on 23 occasions. Both telemetry and visual data indicated that Olrog’s Gull fed almost exclusively within the inlet. In all, 85% of mapped locations (N = 93) were within 3 km of the colony, near the mouth of the inlet. The birds were consistent in the use of one particular area, and most of the tracked birds foraged mainly in one or two areas. Mean number of trips per day was 4.1 ± 0.99 (range = 1-9) and mean trip duration was 109 ± 31.2 min (range = 15-645 minutes). Both variables differed significantly among individuals. Gulls foraged at all states of the tide, although all eight individuals were more likely to forage during mid and low tides than during high tides. The small foraging range of Olrog’s Gull is defined by the spatial extension of intertidal habitats with crabs, being their main prey during the breeding season. Our results confirm the relatively high ecological specialization of Olrog’s Gulls shown in previous diet studies and their dependence on intertidal areas with grapsid crabs.

Pablo Yorio, Flavio Quintana, Alejandro Gatto, Nora Lisnizer, and Nicolás Suárez "Foraging Patterns of Breeding Olrog’s Gull at Golfo San Jorge, Argentina," Waterbirds 27(2), 193-199, (1 June 2004). https://doi.org/10.1675/1524-4695(2004)027[0193:FPOBOG]2.0.CO;2
Received: 28 November 2003; Accepted: 1 February 2004; Published: 1 June 2004
foraging patterns
Larus atlanticus
Olrog’s Gull
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