Foraging Trip Duration Research Articles

Annual variation in diets, feeding locations and foraging behaviour of gannets in the North Sea: flexibility, consistency and constraint

Many seabirds nesting in areas bordering the North Sea have recently experienced large annual variation in breeding success, including reproductive failures in some cases. In contrast, the breeding success of northern gannets Morus bassanus has remained remarkably stable. The present study examines data from the large gannet colony at the Bass Rock (southeast Scotland) across 3 years, to assess the extent to which such stability may reflect both flexibility and consistency in diets and foraging behaviour. Adults exhibited great flexibility both in the species and sizes of prey consumed and in foraging trip durations, ranges and total distances travelled. They also showed a high degree of consistency in bearings of foraging trips and in behaviour at sea; the sinuosity of foraging tracks and average speed of travel was very similar each year and birds in all years spent about half their time at sea in flight. Adults returned to the nest at higher speeds from more distant foraging locations up to ca. 300 km from the colony, but speeds decreased for the farthest destinations (>ca. 400 km). Moreover, the relationship between trip duration and distances travelled at sea was asymptotic beyond ca. 60 h. These non-linear relationships probably reflected constraints on energy expenditure during flight. As a result, nest attendance was low in years with long average trip durations and chicks were left unattended and vulnerable to attack by conspecifics. These data suggest that while adults have so far been able to maintain high reproductive success in years of low prey availability, they may not be able to do so in future years if providing sufficient food for chicks entails any further increases in trip duration or foraging effort.

The winter distribution of chinstrap penguins from two breeding sites in the South Shetland Islands of Antarctica

Satellite telemetry was used to determine the winter movements of eight chinstrap penguins from two breeding colonies in the South Shetland Islands, Antarctica during the 2000 and 2004 austral winters. Chinstrap penguins foraged largely inshore, on the shelf, north of the South Shetland Islands during 2000, but foraged mainly offshore in pelagic waters in 2004. Analyses of foraging trip durations during the chick-rearing periods that preceded the 2000 and 2004 winters suggest that prey were more abundant inshore during the summer of 2000 than in 2004. Oceanographic data further revealed the presence of a strong shelf-slope front in 2000 that was absent in 2004. In addition, two of the six chinstrap penguins from the colony in Admiralty Bay migrated from the South Shetland Islands region to the vicinity of the South Orkney and South Sandwich Islands, distances of 800 and 1,300 km, respectively. We postulate that the differences in winter migratory behavior among chinstrap penguins from this colony may reflect individual ties to different ancestral epicenters of chinstrap populations; one older and local in the South Shetland Islands and one relatively recent, arising from the emigration of chinstrap penguins that occurred during the expansion of this species in the mid-1900s.

Oceans apart: conservation models for two temperate penguin species shaped by the marine environment

Oceanographic productivity patterns in the breeding areas of Magellanic penguins Spheniscus magellanicus in the Atlantic differ from those of Humboldt penguins S. humboldti in the Pacific. We used satellite telemetry to compare foraging trips between 2 Humboldt penguin females with chicks and 44 Magellanic penguin females with eggs or chicks. The Humboldt penguins took trips of short duration and distance, with fewer than 10% of locations >25 km from the colony. Magellanic penguins traveled longer and more variable distances. Only 24% of locations during chick rearing were within 25 km of the colony; all 8 incubation trips reached distances greater than 100 km. Among Magellanic penguins, foraging trip duration was significantly correlated with distance from the colony during all stages of the breeding season (incubation r 2 = 0.66; early chick r 2 = 0.75; late chick r 2 = 0.91). For each hour of trip duration, penguins ranged nearly 1 km farther from the colony. For the 2 Humboldt females, trip duration was correlated with maximum distance from the colony for one female but not the other, whose trip duration varied little. Trip duration for Magellanic penguins determined by nest checks was correlated with duration determined by satellite telemetry (r 2 = 0.96), making nest checks a potentially inexpensive and minimally disturbing estimator of foraging trip distance and changing food availability. The large difference in foraging distance between the species reflects the distribution of productivity in their foraging areas and shows that protecting the species requires conservation models that are effective on different spatial scales.

Foraging behaviour of sympatric Antarctic and subantarctic fur seals: does their contrasting duration of lactation make a difference?

The duration of periods spent ashore versus foraging at sea, diving behaviour, and diet of lactating female Antarctic (Arctocephalus gazella, AFS) and subantarctic (A. tropicalis, SFS) fur seals were compared at Iles Crozet, where both species coexist. The large disparity in lactation duration (SFS: 10 months, AFS: 4 months), even under local sympatry, has led to the expectation that AFS should exhibit higher foraging effort or efficiency per unit time than SFS to allow them to wean their pups in a shorter period of time. Previous evidence, however, has not supported these expectations. In this study, the distribution of foraging trip durations revealed two types of trips: overnight (OFT, 1 day), in common with other results from Macquarie Island. However, diving behaviour differed significantly between foraging trip types, with greater diving effort in OFTs than in LFTs, and diving behaviour differed between fur seal species. OFTs were more frequent in SFS (48%) than in AFS (28%). SFS performed longer LFTs and maternal attendances than AFS, but spent a smaller proportion of their foraging cycle at sea (66.2 vs. 77.5%, respectively). SFS dove deeper and for longer periods than AFS, in both OFTs and LFTs, although indices of diving effort were similar between species. Diel variation in diving behaviour was lower among SFS, which foraged at greater depths during most of the night time available than AFS. The diving behaviour of AFS suggests they followed the nychthemeral migration of their prey more closely. Concomitant with the differences in diving behaviour, AFS and SFS fed on the same prey species, but in different proportions of three myctophid fish (Gymnoscopelus fraseri, G. piabilis, and G. nicholsi) that represented most of their diet. The estimated size of the most important fish consumed did not vary significantly between fur seal species, suggesting that the difference in dive depth was mostly a result of changes in the relative abundance of these myctophids. The energy content of these fish at Iles Crozet may thus influence the amount and quality of milk delivered to pups of each fur seal species. These results contrast with those found at other sites where both species coexist, and revealed a scale of variation in foraging behaviour which did not affect their effort while at sea, but that may be a major determinant of foraging efficiency and, consequently, maternal investment.

Effects of Dummy Global Location Sensors on Foraging Behavior of Cook's Petrel (Pterodroma cookii)

The effect of 4.5-g dummy geolocation loggers on the foraging ability of Cook's Petrel (Pterodroma cookii) was assessed over single foraging trips from Little Barrier Island, New Zealand. I compared foraging trip duration and chick provisioning between equipped and unequipped birds and could not detect a detrimental effect of loggers on either parameter. The lack of effect of these loggers may be the result of their small size, the short-term nature of their use, and foraging strategies used by Cook's Petrel. Geolocation studies involving Cook's Petrel and other small gadfly petrel species may be feasible for single foraging trips.

Conservation implications of the apparent mismatch between population dynamics and foraging effort in French northern gannets from the English Channel

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 319:15-25 (2006) - doi:10.3354/meps319015 Conservation implications of the apparent mismatch between population dynamics and foraging effort in French northern gannets from the English Channel David Grémillet1,2,*, Lorien Pichegru1,3, François Siorat4, Jean-Yves Georges1 1Centre National de la Recherche Scientifique, DEPE-IPHC, 23 rue Becquerel, 67087 Strasbourg Cedex 02, France 2DST/NRF Centre of Excellence, Percy FitzPatrick Institute, University of Cape Town, 7701 Rondebosch, South Africa 3Université Louis Pasteur, 4 rue Blaise Pascal, 67070 Strasbourg, France 4Station Ornithologique de l’Ile Grande, Ligue Pour la Protection des Oiseaux, 22560 Pleumeur-Bodou, France *Email: david.gremillet@c-strasbourg.fr ABSTRACT: Human activities affect all trophic levels of marine food webs and threaten numerous species. The status of such populations can be assessed via monitoring of their size. However, in long-lived species such as most marine top predators, environmental stress on a population only affects its size after several years. It has therefore been suggested that behavioural proxies such as foraging effort could be used to assess the short-term effects of environmental conditions on the wellbeing of a predator population. We demonstrate the potential of this approach in northern gannets Morus bassanus from the Sept-Iles Archipelago, France. This colony has been expanding rapidly for the past 60 yr, and is still growing faster than predicted from its size. However, using miniaturised GPS & time-depth recorders attached to 21 breeding adults, we show that their foraging effort (assessed during the 2005 breeding season in terms of foraging trip duration and diving frequency) is higher than that of their British relatives. Further parameters such as foraging path length, path sinuosity, maximum foraging range, flight speed, flight time, dive depth, dive duration, and diet were also recorded. Using these field data and energetics modelling we predict that northern gannets breeding at the Sept-Iles will be highly sensitive to alterations of their foraging conditions. GPS-tracking indicates that birds from this colony forage exclusively within the western English Channel, with a strong preference for the tidal front between eastern and western Channel waters, northwest of Guernsey. This frontal zone attracts a wide range of marine organisms. It is also heavily fished, and a major oil spill hotspot. We conclude that the conservation of this marine area is critically important for northern gannets breeding at the Sept-Iles Archipelago. KEY WORDS: GPS tracking · Interactions with fisheries · Marine protected areas · Marine top predators · Morus bassanus · Seabird oiling · Tidal front Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 319. Online publication date: August 18, 2006 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2006 Inter-Research.

Foraging trip duration of bumblebees in relation to landscape‐wide resource availability

Abstract 1. The study tested the hypotheses that bumblebees have shorter foraging trips in environments that provide abundant resources than in environments that provide sparse resources, and that shorter foraging trips translate into greater colony growth.2. Six even‐aged Bombus terrestris colonies were established in contrasting resource environments. Three colonies had access to abundant resources (Phacelia tanacetifolia fields with high flower densities), and three colonies were placed in an environment with sparse resources (scattered semi‐natural habitats with food plants at lower densities).3. A total of 870 foraging trips of 220 marked B. terrestris foragers were observed using automated camcorder recordings.4. The duration of foraging trips was shorter in environments with abundant resources (66 ± 4.6 min) than in environments with sparse resources (82 ± 3.7 min). Within 34 days colonies that had access to abundant resources gained significantly more weight (129 ± 40 g) than colonies foraging on sparse resources (19 ± 7 g).5. Thus, the spatial distribution and quality of resources at landscape level affected the duration of foraging trips and the colony growth. It was concluded that future conservation schemes need to improve the spatial and temporal availability of resources in agricultural landscapes to counteract the ongoing decline of bumblebees.

Effects of Flipper Bands on Foraging Behavior and Survival of Adélie Penguins (Pygoscelis Adeliae)

Abstract Since the 1950s, flipper bands have been used widely to mark penguins (Spheniscidae), but not without concerns regarding possible negative effects on survival and fitness. As part of a demographic study of Adélie Penguins (Pygoscelis adeliae) in the western Ross Sea, Antarctica, we investigated effects of flipper bands on foraging-trip duration and food loads, as well as apparent survival, during four breeding seasons (2000-2003), using mark-recapture and radio-frequency identification (RFID) technology. Foraging-trip durations were ∼8% (3.5 h) longer, on average, for banded compared with unbanded birds, but the effect varied among years. Food loads did not differ between banded and unbanded birds, but males carried heavier food loads than females. Flipper bands decreased apparent annual survival by 11–13% during 2000-2003, but over a longer time period (1996-2003) we observed high annual variability, including years of high survival for banded birds. Males had slightly higher survival than females in both banded and unbanded birds. Mechanisms resulting in band effects on foraging behavior and survival, the variable effect of bands by season, and the potential ameliorating effect of age or experience on the effects of bands need further investigation in Adélie and other penguin species. We recognize a need to understand and balance the negative consequences of flipper bands for penguins against the beneficial gains in information associated with their use. Effets du Baguage à l'Aileron sur le Comportement de Recherche Alimentaire et la Survie de Pygoscelis adeliae

INTERSEASONAL AND INTERANNUAL MEASURES OF MATERNAL CARE AMONG INDIVIDUAL STELLER SEA LIONS (EUMETOPIAS JUBATUS)

We studied maternal care in Steller sea lions (Eumetopias jubatus) at a small rookery in the northern Gulf of Alaska over the course of 4 summers, 2001–2004 and 3 autumn seasons, 2002–2004, using remotely operated video cameras. Perinatal periods were long (� 10.0 days); although varied between years. Timing of parturition was earlier and perinatal periods longer for multiparous females compared to females considered to be primiparous. Summer foraging trip durations were short (X ¼ 16.5 h), increased during August, then did not change significantly over the course of the autumn (X ¼ 55.7 h). Individual lactating females spent a greater proportion of their time on shore during the summer and a greater proportion of their time at sea during the autumn. The amount of time that females nursed their pups also increased significantly from the summer to autumn. Long perinatal periods and short foraging trips during summer indicate that sea lions are likely finding sufficient food nearby. Our data also suggest that Steller sea lions reach an upper plateau in duration of foraging cycles as early as mid-August and large increases above that plateau may indicate difficulty finding sufficient food during the winter months.

Impact of El Niño on the foraging behavior of female northern elephant seals

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 309:1-10 (2006) - doi:10.3354/meps309001 Impact of El Niño on the foraging behavior of female northern elephant seals Daniel E. Crocker1,*, Daniel P. Costa2, Burney J. Le Boeuf2, Paul M. Webb3, Dorian S. Houser1 1Department of Biology, Sonoma State University, 1801 East Cotati Road, Rohnert Park, California 94928, USA 2Department of Biology, Institute of Marine Sciences, University of California, Santa Cruz, California 95064, USA 3Department of Biology, Roger Williams University, One Old Ferry Road, Bristol, Rhode Island 02809, USA *Email: crocker@sonoma.edu ABSTRACT: Our aim was to examine the foraging behavior of northern elephant seals Mirounga angustirostris during the 1997–98 El Niño and compare it to foraging in others years. Given their deep diving and spatial distribution, their immediate response to a severe El Niño was expected to give insight into the timing, scale and magnitude of El Niño Southern Oscillation impacts on a large marine predator. Time-depth records and Argos-linked satellite tracks were obtained from adult females departing on post-breeding foraging migrations from 1990 to 1999, including females foraging during the 1998 El Niño. Rates of mass gain and trip duration were recorded for females from 1983 to 1999. Movement tracks of females in 1998 were similar to those observed in non-El Niño years. Rate of mass gain at sea was 0.29 ± 0.36 kg d–1 in 1998, the lowest measured since 1983. Marked declines in the mass gain rate of females were noted in severe El Niño years, but not in moderate El Niño years. Females increase spring foraging trip duration to compensate for decreases in foraging success. In 1998, the frequency distribution and temporal pattern of dive shapes suggested reduced residence time in prey patches and increased travel time between patches and these parameters showed a strong relationship with rates of mass gain. Our data confirm that the immediate ecological impact of the 1997–98 El Niño was not limited to the near-shore coastal margin, but extended far out into the North Pacific Ocean. KEY WORDS: El Niño · Foraging · Seals · Water temperature · Prey patches Full text in pdf format NextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 309. Online publication date: March 15, 2006 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2006 Inter-Research.

EFFECTS OF FLIPPER BANDS ON FORAGING BEHAVIOR AND SURVIVAL OF ADÉLIE PENGUINS (PYGOSCELIS ADELIAE)

Abstract Since the 1950s, flipper bands have been used widely to mark penguins (Spheniscidae), but not without concerns regarding possible negative effects on survival and fitness. As part of a demographic study of Adelie Penguins (Pygoscelis adeliae) in the western Ross Sea, Antarctica, we investigated effects of flipper bands on foraging-trip duration and food loads, as well as apparent survival, during four breeding seasons (2000-2003), using mark-recapture and radio-frequency identification (RFID) technology. Foraging-trip durations were ∼8% (3.5 h) longer, on average, for banded compared with unbanded birds, but the effect varied among years. Food loads did not differ between banded and unbanded birds, but males carried heavier food loads than females. Flipper bands decreased apparent annual survival by 11–13% during 2000-2003, but over a longer time period (1996-2003) we observed high annual variability, including years of high survival for banded birds. Males had slightly higher survival than femal...

Is food availability limiting African Penguins Spheniscus demersus at Boulders? A comparison of foraging effort at mainland and island colonies

The African Penguin Spheniscus demersus (Vulnerable) formed three new colonies during the 1980s, two on the South African mainland (Stony Point and Boulders) and one on Robben Island. One of the mainland colonies, at Boulders, Simon's Town, is in a suburban area, resulting in conflict with humans. Growth of the Boulders colony was initially rapid, largely through immigration, but has since slowed, possibly as a result of density‐dependent effects either on land (where there has been active management to limit the spread of the colony) or at sea. We test the latter hypothesis by comparing the foraging effort of Penguins feeding small chicks at island and mainland sites, and relate this to the foraging area available to birds. Three‐dimensional foraging paths of African Penguins were reconstructed using GPS and time–depth loggers. There were no intercolony differences in the rate at which birds dived during the day (33 dives/h), in diving depths (mean 17 m, max. 69 m) or in travelling speeds. The maximum speed recorded was 2.85 m/s, with birds travelling faster when commuting (average 1.18 m/s) than when foraging (0.93 m/s) or resting at sea (0.66 m/s during the day, 0.41 m/s at night). There were strong correlations between foraging trip duration, foraging range and total distance travelled. Foraging effort was correlated with chick age at Robben Island, but not at Boulders. Contrary to Ashmole's hypothesis, birds from Boulders (c. 1000 pairs) travelled further (46–53 km) and foraged for longer (13.2 h) than did birds from Robben Island (c. 7000 pairs) and Dassen Island (c. 21 000 pairs) (33 km, 10.3 h). The mean foraging range also differed significantly between mainland (18–20 km) and island colonies (9 km). The area available to central‐place‐foraging seabirds breeding on the mainland is typically less than that for seabirds breeding on islands, but the greater foraging range of Boulders birds results in an absolute foraging area roughly twice that of island colonies, and the area per pair is an order of magnitude greater for the relatively small Boulders colony. Ashmole's hypothesis assumes relatively uniform prey availability among colonies, but our results suggest this does not apply in this case. The greater foraging effort of Boulders birds probably reflects reduced prey availability in False Bay, and thus the recent slowing in growth at the colony may be the result of differential immigration rather than management actions to limit the spatial growth of the colony.

Breeding and Overwintering Ecology of Shy Albatrosses in Southern Australia: Year-Round Patterns of Colony Attendance and Foraging-Trip Durations

AbstractWe used radio-transmitters to study year-round patterns of colony attendance and foraging trip duration of Shy Albatrosses (Thalassarche cauta) at Albatross Island (1995–1997) and Pedra Branca (1997), Tasmania, Australia. Colony activity was largely diurnal, and foraging trip, incubation, and brooding shift durations were relatively short throughout the breeding season, consistent with foraging just a few hundred kilometers from the colonies. Shift durations decreased from 2.9 days early in incubation to an average of 24 hr during brooding. Foraging trip durations were similarly short in the first month postbrooding, but then doubled thereafter to approximately 2 days. Attendance and foraging-trip characteristics were similar between years and at both breeding sites. Both early in incubation and late in chick-rearing, females tended to undertake longer foraging trips than males. There was also an increased probability of failure if females spent as much time on the nest as males during incubation. Outside the breeding season, adults were relatively sedentary. Successful parents from Albatross Island forage off southeast Australia for just nine weeks before returning to spend much of the nonbreeding period attending the colony. The close proximity of the feeding and breeding grounds and near year-round presence of adults at the colony reflects locally favorable foraging conditions. Operating within this environment, Shy Albatrosses exhibit breeding, foraging, and provisioning characteristics that represent an extreme within the Diomedeidae.Ecología de Cría y del Período Invernal de Thalassarche cauta en el Sur de Australia: Patrones Anuales de Presencia en la Colonia y Duración de los Viajes de ForrajeoResumen. Usamos radio-transmisores para estudiar los patrones anuales de presencia en la colonia y la duración de los viajes de forrajeo de Thalassarche cauta en Albatross Island (1995–1997) y en Pedra Branca (1997), Tasmania, Australia. La actividad de la colonia fue mayormente diurna, y los viajes de forrajeo, la incubación y la duración de los turnos para empollar fueron relativamente cortos durante la estación de cría, lo que es consistente con que las aves forrajean a unos pocos cientos de kilómetros de la colonia. La duración de los turnos disminuyó de 2.9 días al principio de la incubación a un promedio de 24 hr durante el período de empollamiento. La duración de los viajes de forrajeo fue similarmente corta en el primer mes luego del período de cría, pero después se duplicó hasta aproximadamente 2 días. Las características de la presencia en la colonia y de los viajes de forrajeo fueron similares entre años y en ambos sitios de cría. Las hembras tendieron a realizar viajes de forrajeo más prolongados que los machos tanto a principios de la incubación como a fines del período de cría de los pichones. También hubo una probabilidad mayor de fracaso si las hembras permanecieron en los nidos durante el período de incubación la misma cantidad de tiempo que los machos. Fuera del período de cría, los adultos fueron relativamente sedentarios. Los padres exitosos de Albatross Island forrajearon en el mar del sudeste de Australia solamente durante nueve semanas antes de regresar a pasar gran parte del período no reproductivo en la colonia. La proximidad de los sitios de alimentación y de cría y la presencia casi completa a lo largo del año de los adultos en la colonia reflejan condiciones locales favorables de forrajeo. En sintonía con el ambiente, T. cauta presenta características reproductivas, de alimentación y de aprovisionamiento que son extremas entre los Diomedeidae.

Sex‐specific foraging behaviour in tropical boobies: does size matter?

Sex differences in the foraging behaviour of adults have been observed in a number of sexually size‐dimorphic birds, and the usual inference has been that these sex‐specific differences are driven primarily by differences in body size. An alternative explanation is that foraging differences result from sex differences unrelated to size, such as sex‐specific nutritional requirements. To examine these alternative hypotheses, the foraging behaviour of parents was compared between two sympatric and congeneric species of seabird, the Brown Booby Sula leucogaster, which is highly sexually size‐dimorphic (females 38% larger) and the Red‐footed Booby S. sula, in which sex differences in body size are less marked (females 15% larger). Using temperature and depth loggers, we found that there were highly significant differences in the foraging trip durations and diving behaviour of male and female Brown Boobies. These sex differences were less marked in Red‐footed Boobies. Thus, our interspecies comparison revealed that the magnitude of the difference between the sexes matched the sexual size dimorphism of the species, providing support for the size hypothesis.

Orientation in the wandering albatross: interfering with magnetic perception does not affect orientation performance

After making foraging flights of several thousands of kilometers, wandering albatrosses (Diomedea exulans) are able to pinpoint a specific remote island where their nests are located. This impressive navigation ability is highly precise but its nature is mysterious. Here we examined whether albatrosses rely on the perception of the Earth's magnetic field to accomplish this task. We disturbed the perception of the magnetic field using mobile magnets glued to the head of nine albatrosses and compared their performances with those of 11 control birds. We then used satellite telemetry to monitor their behavior. We found that the ability of birds to home specific nest sites was unimpaired by this manipulation. In particular, experimental and control birds did not show significant differences with respect to either foraging trip duration, or length, or with respect to homing straightness index. Our data suggest that wandering albatrosses do not require magnetic cues to navigate back to their nesting birds.

Spatial and temporal variation in the provisioning behaviour of female rockhopper penguins Eudyptes chrysocome filholi

As seabirds are central place foragers during breeding, their provisioning behaviour and their ability to face variable energy demand from the chicks is expected to vary with environmental conditions. The provisioning behaviour of female rockhopper penguins Eudyptes chrysocome filholi was recorded over the chick‐rearing period at Kerguelen (KER) and Crozet (CRO) archipelagoes (two very distinct marine environments), using time‐depth recorders, or VHF transmitters coupled with an automatic recording station. No influences of the method have been found on the average foraging trip durations. Some previously undescribed short and multiple trips within a day were recorded using the automatic recording system. These multiple trips (6.8 h) were mostly performed with <5 days old chicks, a period during which feeding rates were the highest (1.1 meals per day), at both sites. During the brooding period, both KER and CRO females mainly performed daily trips of increasing duration (2 h longer at CRO) and at decreasing frequency. During the crèche compared to the brooding period, females from KER performed slightly fewer daily trips (0.6 per day) and more (<3 days) overnight trips, while females from CRO performed very few daily trips (0.1 per day) and more overnight trips, some of them being long trips lasting 5 to 29 days, mostly initiated during the transition between the brooding and the crèche periods. The result fit the hypothesis that long trips permit females to restore and/or maintain their body condition at more distant foraging places. It seemed that chick developement during the brooding period and environmental factors during the crèche period conditioned trip duration of females. Due to more long trips at CRO, the female feeding frequency was twice as high at KER than at CRO during the crèche period, while males participated in the feeding duties. Based on differences in female behaviour, we hypothesize that the male's contribution is likely to differ strongly from one site to another, and may buffer the possible decrease in female feeding frequency by feeding the chicks if food is less abundant.

Foraging performance and reproductive success of Humboldt penguins in relation to prey availability

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 296:173-181 (2005) - doi:10.3354/meps296173 Foraging performance and reproductive success of Humboldt penguins in relation to prey availability J. C. Hennicke1,*, B. M. Culik2 1Zoologisches Institut und Museum, Universität Hamburg, Martin-Luther-King-Platz 37, 20146 Hamburg, Germany2Institut für Meereskunde, Düsternbrooker Weg 20, 24105 Kiel, Germany *Email: janos.hennicke@uni-hamburg.de ABSTRACT: During the austral summer 1998/1999, we compared foraging ecology and reproduction between chick-rearing Humboldt penguins Spheniscus humboldti at 2 colonies in Chile. At Pan de Azúcar in northern Chile prey availability was assumed to be lower than at Puñihuil, 1500 km further south, according to oceanographic data. Fifteen adult penguins were equipped with temperature-depth recorders and stomach-temperature-loggers in order to investigate foraging effort and foraging success in relation to differences in prey availability. There were no differences between colonies in diving behaviour. At Pan de Azúcar, foraging trips were longer than at Puñihuil (mean duration 36.5 ± 7.8 h vs. 19.0 ± 8.7 h), resulting in higher energy expenditure per foraging trip (on average 8092.7 ± 2216.7 kJ vs. 3934.5 kJ, range: 3071 to 7930 kJ). Catch per unit effort at Pan de Azúcar equalled 2.2 ± 1.4 g min–1 under water, which was significantly less than 10.0 ± 7.3 g min–1 at Puñihuil. As a result of higher energetic costs and lower foraging success, the gross foraging efficiency per foraging trip (GFE) was lower at Pan de Azúcar than at Puñihuil (on average 0.94 ± 0.52 vs. 4.61 ± 3.4 [kJ gained/kJ invested]). The chick growth rates at Pan de Azúcar (mass: 40.0 ± 18.4 g d–1 vs. 63.0 ± 23.0 g d–1; bill length: 0.32 ± 0.07 mm d–1 vs. 0.47 ± 0.12 mm d–1), as well as chick survival (40% vs. 100%) and reproductive success (0.33 vs. 0.81 fledglings nest–1), were lower compared to Puñihuil. A GFE threshold of 1.08 was calculated for chick survival at Pan de Azúcar. We conclude that due to physiological and morphological constraints the penguins at Pan de Azúcar could not increase diving effort to compensate for lower prey availability, but took extended foraging trips instead. Therefore, foraging efficiency and meal delivery rate decreased, resulting in less chick growth and lower reproductive success. KEY WORDS: Gross foraging efficiency · Humboldt penguin · Diving behaviour · Foraging trip duration · CPUE · Reproductive success Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 296. Online publication date: July 12, 2005 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2005 Inter-Research.

Inter-sexual differences in New Zealand fur seal diving behaviour

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 304:249-264 (2005) - doi:10.3354/meps304249 Inter-sexual differences in New Zealand fur seal diving behaviour Brad Page1,2,*, Jane McKenzie1, Simon D. Goldsworthy1,2 1Sea Mammal Ecology Group, Zoology Department, La Trobe University, Bundoora Campus, Victoria 3086, Australia2Present address: South Australian Research and Development Institute (Aquatic Sciences), PO Box 120, Henley Beach,South Australia 5022, Australia *Email: b.page@latrobe.edu.au ABSTRACT: We studied the diving behaviour of adult male and lactating female New Zealand fur seals Arctocephalus forsteri to determine inter-sexual differences in their foraging strategies. Adult male fur seals are significantly longer and heavier than lactating females. Lactating females are central place foragers that regularly provision dependent pups, and consequently females conducted shorter duration foraging trips (5.0 ± 3.7 d) compared to the relatively unconstrained adult males (9.0 ± 3.9 d). Male trip durations were not correlated to variables that measured individuals’ dive effort. In lactating females, foraging trip duration was significantly, positively correlated to the number of dives h–1 and negatively correlated with the mean dive duration at night. This indicates that females on longer trips invested relatively more time searching for prey patches, which they utilised on relatively short duration dives. Males and females typically dived at night and appeared to utilise both pelagic and benthic habitats. Males dived deeper (max = 380+ m, mean = 52.1 ± 59.3 m) and for longer (max = 14.8 min, mean = 3.6 ± 2.5 min) than females (max = 312 m and 9.3 min, mean = 41.5 ± 26.8 m and 2.7 ± 1.3 min). Inter-sexual foraging competition is likely to be minimal in this species, because females typically utilised continental shelf waters and males foraged in deeper waters over the continental shelf break, beyond female foraging grounds. Inter-sexual differences in fur seal diving behaviour most likely result from sexual dimorphism, which places different physiological constraints on the diving performance of males and females. KEY WORDS: Arctocephalus · Sexual segregation · Foraging ecology · Resource partitioning Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 304. Online publication date: December 08, 2005 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2005 Inter-Research.

BREEDING AND OVERWINTERING ECOLOGY OF SHY ALBATROSSES IN SOUTHERN AUSTRALIA: YEAR-ROUND PATTERNS OF COLONY ATTENDANCE AND FORAGING-TRIP DURATIONS

Abstract We used radio-transmitters to study year-round patterns of colony attendance and foraging trip duration of Shy Albatrosses (Thalassarche cauta) at Albatross Island (1995–1997) and Pedra Branca (1997), Tasmania, Australia. Colony activity was largely diurnal, and foraging trip, incubation, and brooding shift durations were relatively short throughout the breeding season, consistent with foraging just a few hundred kilometers from the colonies. Shift durations decreased from 2.9 days early in incubation to an average of 24 hr during brooding. Foraging trip durations were similarly short in the first month postbrooding, but then doubled thereafter to approximately 2 days. Attendance and foraging-trip characteristics were similar between years and at both breeding sites. Both early in incubation and late in chick-rearing, females tended to undertake longer foraging trips than males. There was also an increased probability of failure if females spent as much time on the nest as males during incubation...

Flexible foraging patterns under different time constraints in tropical boobies

The foraging behaviour of any animal is intricately linked to ecological constraints. Extrinsic factors, such as daylength, may limit the time available for foraging. Intrinsic factors, such as the coordination of mates at a nest site, may exacerbate this limitation. Using activity loggers, we examined the effects of extrinsic and intrinsic limitations on the foraging behaviour of the sympatric red-footed booby, Sula sula, and brown booby, Sula leucogaster, during incubation, and tested the prediction that individuals would work harder when time available for foraging was limiting. Both species share incubation duties and forage by day. Brown boobies made significantly shorter foraging trips than red-footed boobies, and thus, both parents could forage during the same day. Therefore, departure time and time available for foraging will also be influenced by when the partner returns to the colony. Overall foraging trip duration decreased linearly with respect to departure time. Our study suggests that the time available for foraging is limited by a combination of extrinsic and intrinsic processes in both species. Crucially, the rate of flying and diving, indicators of prey search and pursuit, respectively, increased with decreasing time available for foraging, whereas time spent inactive on the sea surface decreased, as did the time between departure and diving. Our data therefore suggest that boobies adjust their foraging behaviour according to extrinsic constraints.