Distribution and foraging behaviour of the Peruvian Booby (Sula variegata) off northern Chile

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: Comparison With Other Sitesmentioning

confidence: 72%

Section: Comparison With Other Sitesmentioning

confidence: 99%

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

Weimerskirch¹,

Bertrand²,

Silva³

et al. 2012

“…Likewise, trip length was not a good predictor of maximum foraging distance on LT because birds spent a considerable amount of time exploring waters along the coast- line. Coastal feeding has also been observed in Peruvian boobies from Isla Pajaros (< 25 km offshore) in northern central Chile (Ludynia et al 2009). However, birds from the offshore island of LA never approached the mainland coast, indicating that breeding Peruvian boobies are not exclusively inshore feeders.…”

Section: Discussionmentioning

confidence: 83%

“…The Peruvian booby Sula variegata is recognized as one of the most abundant seabirds of the Humboldt Current System , Weichler et al 2004, with a population size in Peru at the end of 1999 of approximately 1.5 million birds (Goya 2000). Peruvian boobies in northern central Chile feed mainly on anchoveta, mackerel Trachurus murphyi and king gar Scomberesox saurus that are captured in coastal areas relatively close to their colonies (Ludynia et al 2009). In Peru, they feed almost exclusively on anchoveta (Jahncke & Zileri 1998, Tovar & Guillén 1988, Jahncke & Goya 2000 obtained by rapid, shallow plunge dives (Nelson 1978, Duffy 1987.…”

Section: Introductionmentioning

confidence: 99%

At-sea movement patterns and diving behavior of Peruvian boobies Sula variegata in northern Peru

Zavalaga¹,

Halls²,

Mori³

et al. 2010

GPS loggers and time-depth recorders were used to characterize the foraging behavior of the sexually dimorphic Peruvian booby Sula variegata on 2 islands in northern Peru. We evaluated whether (1) its foraging behavior differed from tropical boobies and temperate gannets (the Peruvian boobies feed in areas of enhanced productivity and high fish density), and (2) females and males exploited different foraging habitats as a consequence of size dimorphism. Birds foraged only during daylight hours, 1 to 3 times a day, in trips of short duration (median = 1.8 h). Overall, 92% of the total foraging time was spent flying. They fed exclusively on anchovetas Engraulis ringens, which were captured in shallow dives (median = 2.5 m, max = 8.8 m) with a dive median rate of 11 dives h -1 (max = 37 dives h -1 ). The median foraging range was 25 km (max = 68 km), whereas the median total distance traveled was 69 km (max = 179 km). Foraging site fidelity was high, and the orientation of foraging flights in any given day was similar among birds that departed at the same time. There were no sex-specific differences in 13 of 15 foraging variables; however, females dived slightly deeper and spent a larger proportion of time sitting on the water. We speculate that (1) the foraging behavior of Peruvian boobies contrasts with that of their tropical and temperate relatives as a result of the proximity and predictability of food sources, elevated energetic demands of the brood (up to 4 chicks) and high prey encounter rate in the Peruvian upwelling system, and (2) the lack of spatial segregation between sexes may be related to the attraction of birds to feeding aggregations that are formed in the vicinity of the colonies. Once the foraging patches are localized, females dive deeper because of passive mechanisms associated with a heavier mass.

“…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