Data from: Study "GPS tracking of guanay cormorants"

Abstract

Foraging movements are commonly driven by both extrinsic (e.g. climate or food availability) and intrinsic (e.g. breeding status or nutritional state) factors. In the Humboldt Current System (HCS), a highly productive upwelling system, Peruvian boobies (Sula variegata) and guanay cormorants (Phalacrocorax bougainvillii), are the most abundant guano seabirds. They prey mainly on Peruvian anchovy (Engraulis ringens), a cold-water fish species whose availability decreases during El Niño events (warmer conditions). We studied the relationship between extrinsic and intrinsic factors linked with foraging movements by means of biologging and analysis of metabolites, which reflect the nutritional states of both species during two contrasting breeding seasons (2018 [warm, high nest abandonment]; 2019 [normal, low nest abandonment]) at Guañape Norte Island, Peru (8°32’02.0"S 78°57’47.0"W). Peruvian boobies traveled greater distances on average (69.7 +/- 2.90 km) than guanay cormorants (50.5 +/- 2.13 km). Mean foraging trip duration for both species was greater during the warmer year (2.63 h +/- 0.15 in 2018 vs. 1.97 h +/- 0.1 in 2019), as expected due to reduced prey availability. Ketone concentrations were lower in boobies during the warm year, and cholesterol concentrations decreased with search effort. We conclude that Peruvian seabirds respond to warming of the HCS by increasing foraging effort, which is strongly linked to their nutritional status. Therefore, these warming effects on the system may be detrimental for population recovery in the long-term and need to be addressed in conservation planning such as protected area delimitation and fisheries management during the breeding season.