The three-dimensional flight of red-footed boobies: adaptations to foraging in a tropical environment?

The Humboldt Current System is the most productive upwelling system globally in terms of fish and sustains huge populations of guano-producing birds as well as the world's largest single-species fishery targeting the Peruvian anchovy Engraulis ringens. Peruvian boobies Sula variegata and Guanay cormorants Phalacrocorax bougainvillii are the most abundant seabird species in the system and feed mainly on anchovies. By using high precision GPS and time−depth recorders, we compared the horizontal and vertical movements of the 2 species to examine whether segregation occurs between their foraging areas and whether there is any evidence for prey depletion close to large colonies. A simultaneous acoustic cruise in the foraging area of the 2 bird species estimated the vertical and horizontal distributions of anchovy schools. During the study period in austral spring 2008, the 2 bird species foraged in the same area, at relatively short distance from the colony (average, 19 to 20 km). Both species foraged at similar times of the day, although Peruvian boobies tended to leave earlier in the morning and return later in the evening than did the cormorants. Foraging trips were similar in duration, distance covered and range. Peruvian anchovies were abundant and schools occurred at shallow depths (median, 7 m; range, 3 to 34 m), mainly to the north and west of the colony where foraging bouts of the 2 species overlapped extensively. Cormorants are mainly pelagic surface divers, diving at shallow depths (median, 4 m) but reaching up to 32 m depth, and are thus able to track all the depths at which anchovies occurred during the study period. Peruvian boobies are plunge divers able to reach occasionally 10 m (median, 2 m), and are thus able to reach only shallow anchovy schools. No sexspecific differences in horizontal or vertical movements occurred between males and females in the 2 species. We suggest that the absence of significant differences between horizontal movements of boobies and cormorants, the relative short duration of their trips and the high number of chicks fledged were probably explained by the high abundance and accessibility of anchovies. Differences may be exacerbated during years of low anchovy abundance or accessibility, especially El Niño years. KEY WORDS: Peruvian anchovy · Telemetry · Phalacrocorax bougainvillii · Sula variegataResale or republication not permitted without written consent of the publisher

Section: Sex-specific Differencesmentioning

confidence: 52%

Foraging in Guanay cormorant and Peruvian booby, the major guano-producing seabirds in the Humboldt Current System

Weimerskirch¹,

Bertrand²,

Silva³

et al. 2012

“…The annotation of behaviours was based on 2 input variables: the speed and the turning angle, obtained from successive locations. First, all tracks were linearly interpolated with 1 location every 2 min and the maximum speed was set to 90 km h −1 (Weimerskirch et al 2005b). Each location was clustered by the algorithm into 4 behaviour categories (Table 2): High velocity/Low turn (HL), High velocity/High turn (HH), Low velo city/Low turn (LL), Low velocity/High turn (LH).…”

Section: Track Parameters and Behaviour Labellingmentioning

confidence: 99%

Geographical variation in the foraging behaviour of the pantropical red-footed booby

Mendez¹,

Borsa²,

Cruz³

et al. 2017

While interspecific differences in foraging behaviour have attracted much attention, less is known about how foraging behaviour differs between populations of the same species.Here we compared the foraging strategy of a pantropical seabird, the red-footed booby Sula sula, in 5 populations breeding in contrasted environmental conditions. The foraging strategy strongly differed between sites, from strictly diurnal short trips in Europa Island (Mozambique channel) to long trips including up to 5 nights at sea in Genovesa Island (Galapagos archipelago). The Expectation Maximisation binary Clustering (EMbC) algorithm was used to determine the different behaviours of individuals during their foraging trips (travelling, intensive foraging, resting and relocating). During the day, the activity budget was similar for all the breeding colonies. During the night, birds were primarily on the water, drifting with currents. At all sites, birds similarly performed intensive foraging in zones of area-restricted search (ARS), although the size and duration of ARS zones differed markedly. Red-footed boobies foraged over deep oceanic waters, with chlorophyll a concentrations varying between sites. Birds did not appear to target areas with higher productivity. We suggest that range differences between populations may be linked to other factors such as intra-and interspecific competition.

“…breed and forage in a wide range of habitats, from coastal upwelling environments to a gradient of tropical and subtropical environments. Although all booby species generally have a limited foraging range when breeding (Weimerskirch et al 2005a, 2009c, Zavalaga et al 2008, 2010, Ludynia et al 2010, tropical boobies are also unable to dive deeper than a few meters (Lewis et al 2005, Weimerskirch et al 2005b. Consequently, tropical boobies rarely have access to their prey, and require subsurface marine predators such as tunas or dolphins to force prey towards the surface to enable capture (Au & Pitman 1986).…”

Section: Introductionmentioning

confidence: 99%

Variability of resource partitioning in sympatric tropical boobies

Kappes¹,

Weimerskirch²,

Pinaud³

et al. 2011

Inter-and intraspecific competition can lead to resource partitioning in sympatric species, processes likely affected by environmental productivity and population size. We investigated the foraging behaviour and diet of masked (Sula dactylatra) and red-footed (S. sula) boobies at Tromelin Island, western Indian Ocean, to examine the role of resource partitioning in the foraging strategies of these sympatric species in an extreme oligotrophic environment. We compared our results to published studies with differing environmental conditions or population sizes. We used GPS loggers and Argos transmitters to track foraging movements and used time-depth recorders to estimate dive depths. Masked boobies travelled further and at faster rates than redfooted boobies, and sexes did not differ in foraging behaviour. Based on randomization tests, the foraging range of each species (95% utilization distribution; UD) overlapped significantly. However, at core foraging areas (50% and 25% UD), interspecific segregation was greater than expected by chance alone. No intraspecific spatial segregation was detected between sexes. Environmental characteristics of area-restricted search zones differed between species, but not sexes; masked boobies utilized warmer, deeper, and less windy oceanic environments than red-footed boobies. Masked boobies attained greater diving depths than red-footed boobies and consumed primarily flying fish, whereas red-footed boobies consumed mostly squid. Red-footed and masked boobies breeding in the extreme oligotrophic environment near Tromelin demonstrated greater dietary partitioning differences in foraging ranges compared to a less oligotrophic environment. This suggests that environmental productivity may play a role in processes of resource partitioning in these sympatric species.KEY WORDS: Resource partitioning · GPS · Satellite tracking · Area-restricted search · Diet · Sula dactylatra · Sula sula Resale or republication not permitted without written consent of the publisher