Effect of food deprivation on dominance status in blue-footed booby (Sula nebouxii) broods

A pecking hierarchy is normally established in the usual two-chickbrood of the blue-footed booby (Sula nebouxii). The senior (first-hatched)chick dominates its smaller sibling and receives a greater shareof parentally provided food. Experimental broods were createdby putting together two unrelated junior chicks of die sameage in a vacated foster nest The state of the chicks was manipulatedby a period of controlled artificial feeding so that each chickunderwent a different level of food deprivation. The resultingdominance relationship depended on the relative food deprivationlevel of the chicks: the hungrier chick normally became dominant.However, die effect of hunger was occasionally overruled bysize difference: when die hungrier chick was much smaller thanits foster sibling, it was unable to gain dominance over itslarger companion. Dominance status is likely to have greatervalue for die hungrier chick, while die cost of fighting shouldbe lower for die larger chick. These results conform to dieevolutionarily stable strategy predicted for games widi asymmetricpayoff and differences in resource holding power.     

Effects of breeding success, mate fidelity and senescence on breeding dispersal of male and female blue-footed boobies

1. Understanding the effects of individual and population factors on variation in breeding dispersal (the movement of individuals between successive breeding sites) is key to identifying the strategies behind breeders' movements. Dispersal is often influenced by multiple factors and these can be confounded with each other. We used 13 years of data on the locations, mates, breeding success and ages of individuals to tease apart the factors influencing breeding dispersal in a colonially breeding long-lived seabird, the blue-footed booby Sula nebouxii. 2. Breeding dispersal varied among and within years. Males dispersed further in years of higher population density, and late breeding males and females dispersed further than early breeders. This temporal variation related to changes in competition for territory was taken into account in all tests of individual factors influencing breeding dispersal. 3. Individuals that retained their mates from the previous year dispersed shorter distances than those that changed their mates. 4. The effect of previous breeding success depended on mate fidelity. Unsuccessful breeding induced greater dispersal in birds that changed their mates but not in birds that retained their mates, indicating that breeders who change mates may take their own previous breeding experience into account during habitat selection. Faithful individuals may have to stay close to their previous sites to encounter their mates. 5. Male divorcees dispersed over shorter distances than their former mates, possibly because males contribute more than females to establishing territories. 6. Dispersal of males and females declined with increasing age over the first 10-11 years of life, then increased in old age, possibly due to senescent decay in the ability to compete for mates and territories.     

Mammalian community structure in lowland, tropical Peru, as determined by removal trapping

Amazonian lowland rain forests are complex three-dimensional formations consisting of a variety of arboreal and terrestrial habitats. The small mammal faunas, particularly of arboreal habitats, are poorly studied, and field research generally has been limited to a few faunal inventories. We sampled the terrestrial and arboreal small mammal fauna in two floodplain forest study zones at Reserva Cuzco Amazonico, southeastern Peru, by removal trapping for 12 consecutive days in dry (June-July 1989) and rainy seasons (January-February 1990). Nineteen taxa of marsupials and rodents were captured. Small mammals were more abundant in the rainy season than in the dry season, but the relative proportions of the 11 most abundant species remained stable between seasons and study zones. Most species showed no decline in capture rates through the 12-day period, indicating that either population densities were high or animals were quite mobile. The small mammal fauna exhibited strong vertical stratification; among the 11 most abundant species, four exhibited strong biases toward terrestrial and five toward above-ground captures. The distinct arboreal small mammal community is grossly underrepresented if traps are placed only at ground level.     

Foraging dynamics of muskoxen in Peary Land, northern Greenland

Muskoxen Ovibos moschatus in northern Greenland (79-83°N) are at the northern limit of their distribution and exist under seasonal extremes dominated by nearly 10 months of winter, much of which is without sunlight. The period of summer vegetative growth is less than two months. In the Kap København area (82°30'N), diversity of plant species is low (76 species of vascular plants) and forage biomass in major vegetation types in summer varies from over 40 g m^-2 in sedge-dominated fens to ≤5 g m^-2 in polar barrens. Nonetheless, 90-95% of the ice-free area consists of barren ground or sparcely vegetated polar desert. During summer, muskoxen apparently foraged opportunistically to maximize intake, with sedges the major food item in fens while willows were the major dietary component when on willow-dominated slopes. Quality of summer forage was high during its early phenological stages, with 21-28% crude protein and 60-75% in vitro digestibility. Microhistological analysis of winter feces indicated dominance by graminoids. Muskoxen spent > 50% of their daily activity feeding, which fits a cline of increasing feeding time with increasing latitude in summer. Increased feeding times at high latitudes appears to be a function of both reduced forage biomass and need to maximize forage intake during the brief summer period when forage quality is high. Movement rates in summer while foraging were inversely related to available forage biomass. Seasonal activity of muskoxen peaks during the rutting period (July-September) and then declines gradually through early winter to a low in late winter (March-April).     

Squamate areas of endemism in Cuba as determined by parsimony analysis of endemicity

Cuba, the largest island in the Greater Antilles, hosts a high diversity of native squamate reptiles and is characterized by a complex geological history. The island has undergone repeated submergence and emergence, positioned on the dynamic border between the Caribbean and North American tectonic plates. Here, we infer current areas of endemism on Cuba based on squamate distributions using standard parsimony analysis of endemism under the “areas of endemism as individuals” hypothesis. We diagnose 29 areas of endemism, 14 of which are nested within other areas of endemism, from 52 squamate taxa. We suspect the current biotic pattern is a composite view of layered histories, and we summarize the geological history of the island to contemplate historical periods that left stronger marks on squamate distributions than others.     

Foraging patterns of breeding Dolphin Gulls Larus scoresbii at Punta Tombo, Argentina

The Dolphin Gull Larus scoresbii is a little-known, rare species endemic to southern South America. Knowledge of its feeding ecology is essential for development of management and conservation strategies. To obtain information on their use of food resources and on the frequency and duration of their foraging trips, we followed seven individuals by radiotelemetry during the breeding season of 2002 at the Punta Tombo Reserve, Argentina. In 99% of mapped locations ( n  = 4069) the Gulls were within 2.4 km of their colony. Dolphin Gulls foraged mostly at the colonies of three other species, feeding on Magellanic Penguin Spheniscus magellanicus and Imperial Cormorant Phalacrocorax atriceps regurgitates and on Southern Sea Lion Otaria flavescens faeces. The sea lion colony was the most frequently visited foraging area, accounting for 64% of the total ( n  = 260 trips). A similar trend was observed during both the incubation (60%, n  = 38 trips) and the chick (64%, n  = 40 trips) stages. The mean number of trips per day was 3.8 (range = 3–5), with a mean duration of 123 min (sd = ±27). Trip duration differed between foraging areas, being significantly longer at the sea lion than at the penguin and cormorant colonies. The small foraging range given by its particular feeding strategy suggests that Dolphin Gulls, in contrast to most other seabirds that range over large expanses of ocean in search of food, may be effectively conserved within protected areas during the breeding season.     

Perceived direction of motion determined by adaptation to static binocular images

In Li and Atick's [1, 2] theory of efficient stereo coding, the two eyes' signals are transformed into uncorrelated binocular summation and difference signals, and gain control is applied to the summation and differencing channels to optimize their sensitivities. In natural vision, the optimal channel sensitivities vary from moment to moment, depending on the strengths of the summation and difference signals; these channels should therefore be separately adaptable, whereby a channel's sensitivity is reduced following overexposure to adaptation stimuli that selectively stimulate that channel. This predicts a remarkable effect of binocular adaptation on perceived direction of a dichoptic motion stimulus [3]. For this stimulus, the summation and difference signals move in opposite directions, so perceived motion direction (upward or downward) should depend on which of the two binocular channels is most strongly adapted, even if the adaptation stimuli are completely static. We confirmed this prediction: a single static dichoptic adaptation stimulus presented for less than 1 s can control perceived direction of a subsequently presented dichoptic motion stimulus. This is not predicted by any current model of motion perception and suggests that the visual cortex quickly adapts to the prevailing binocular image statistics to maximize information-coding efficiency.     

Catecholamine biosynthesis in specific brain areas of the rat as determined by liquid chromatography and amperometric detection

Catecholamine turnover is examined using both steady and non-steady state methods. The steady state technique involved the injection of 5 μCi of ³H-tyrosine into the lateral cerebral ventricle in chronically cannulated rats. Catecholamines were separated by high performance reverse phase liquid chromatography and content analyzed with amperometric detection. Catecholamine synthesis was examined in the anterior hypothalamus, medial basal hypothalamus, brain stem and caudate-putamen. Dopamine synthesis was greater than norepinephrine in all areas but the brain stem. The decline in catecholamine content was demonstrated with a synthesis inhibitor, αMpT, and comparisons were made between the two methods. This study indicated that tyrosine hydroxylase inhibition alters catecholaminergic neuronal activity in the brain areas that we examined.     

Foraging behaviour of chick-rearing rhinoceros auklets Cerorhinca monocerata at Teuri Island, Japan, determined by acceleration-depth recording micro data loggers

Flight and diving activity of rhinoceros auklets Cerorhinca monocerata breeding on Teuri Island, Japan, were monitored during the summers 1999 and 2000 using miniaturized time-depth and acceleration recorders. Birds made 14.5 dive bouts per day of on average 15.4 min duration, which consisted of on average 16.2 dives of 12.1 m depth and 42.7 s duration. Birds made 13.8±7.3 flight bouts per day, which lasted on average 11.5±4.5 min. Daily total flight duration was 2.7±1.7 h (range 54 s–5.1 h) and the mean potential foraging range was estimated to be 87 km (maximum 164 km). Most birds stayed at the colony or rested on the water surface during the night. Rhinoceros auklets dived more actively in early morning and in late afternoon than during mid-day. Compared to results from studies of time allocation in other alcids species, rhinoceros auklets spent longer time flying (3.3 hd⁻¹) and resting on water (13.1 hd⁻¹), and less time diving (3.1 hd⁻¹) and staying at the colony (4.4 hd⁻¹). These foraging patterns are probably related to the nest attendance pattern of rhinoceros auklets, i.e. leaving the colony early in the morning, staying at sea all the day and returning to the colony in the evening to provision their chicks.     

Foraging ecology of an assemblage of birds in lowland rainforest in northern Queensland

This paper presents an analysis of the foraging ecologies and hence means of partitioning resources amongst the twenty-eight most conspicuous species of birds in lowland tropical rainforest at Lacey's Creek, North Queensland. The height and site of foraging and the type of behaviour used by the species were compared. The height at which species foraged appeared to be more important for separating species than the site of foraging or the behaviour used. There appeared to be a greater proportion of species with generalized foraging behaviour at Lacey's Creek than in bird communities in the neotropics. Frugivorous species had very similar foraging ecologies but there were differences in the species of fruit eaten by some species. There were seasonal shifts in foraging by some species. It is postulated that the relative shortage of terrestrial species at Lacey's Creek compared with highland forest in North Queensland is due to the harsh dry season in the lowlands. The structure of this bird community appeared to be strongly affected by seasonality of climate.     

Observations on the biogeography of the Amotape-Huancabamba Zone in northern Peru

Some scientists have suggested that the Huancabamba Depression in northern Peru—i.e., the partial interruption of the Andean chain by the Rio Chamaya drainage system—represents a major biogeographical barrier to montane taxa. Others have suggested that the Amotape-Huancabamba Zone in the Andes of northern Peru and the extreme south of Ecuador is an area of particular biological diversity and possibly a phytogeographical zone in its own right. The phytogeography of this area is investigated here with data mainly from the Loasaceae, supplemented by data on other plant and animal groups and by some new data fromPassiflora L. (Passifloraceae) andRibes L. (Grossulariaceae). The Huancabamba Depression itself does not seem to have been a major dispersal barrier for these groups. However, a phytogeographical zone—the Amotape-Huancabamba Zone—between the Río Jubones system in Ecuador and the Río Chamaya system in Peru can be recognized from the available data. This zone seems to be home to numerous endemic species and species groups and has a high level of diversity (6–8 times as high as adjacent areas to the north and to the south in the groups studied). The species of this area show narrow endemicity and often strikingly aberrant morphological characters, compared with representatives of the same groups from other areas. The overlap between northern and southern groups in the area, the mosaic nature of its habitats (geology, geography, and climate), and a varied geological history (habitat fragmentation, secondary contact) seem to be the three most important factors contributing to these patterns of diversification. At least some phylogenetically old taxa appear to have survived in the Amotape-Huancabamba Zone. The region thus seems to be home to a high number of both neoendemics and paleoendemics.     

Frequencies of genotypes of relatives,as determined by stochastic matrices

The ITO method ofLi & Sacks (1954) is extended to simply closed inbreeding systems. Two new matrices I^* and D are introduced. These matrices give the probabilities of descendent genotypes when the ancestor is given and vice versa. The computations of the transition matrices are made less cumbersome by the introduction of an operator-method. The results are extended to multiple alleles (section 2) and to sex-linked loci (section 3). As applications, the computation of genetic correlations (section 4) and of unconditional probabilities (section 6) are considered.     

Molecular areas of phospholipids as determined by 2H NMR spectroscopy. Comparison of phosphatidylethanolamines and phosphatidylcholines.

The role of lipid diversity in biomembranes is one of the major unsolved problems in biochemistry. One parameter of possible importance is the mean cross-sectional area occupied per lipid molecule, which may be related to formation of nonbilayer structures and membrane protein function. We have used 2H NMR spectroscopy to compare the properties of 1,2-diperdeuteriopalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE-d62) and 1,2-diperdeuteriopalmitoyl-sn-glycero-3-phosphocholine (DPPC-d62) in the L alpha phase. We find that DPPE has greater segmental order than DPPC, and that this increase in order is related to the smaller area per acyl chain found for DPPE. Values of the mean cross-sectional chain area are calculated using a simple diamond lattice model for the acyl chain configurational statistics, together with dilatometry data. The results obtained for the mean area per molecule are comparable with those from low angle x-ray diffraction studies.     

Diel locomotor activity of brook charr, as determined by radiotelemetry

Locations by radiotelemetry during eight 24–h sampling periods in 1991, 1992, and 1993 were used to evaluate the diel activity patterns of adult brook charr Salvelinus fontinalis in two lakes of the Laurentian Shield (Québec, Canada). Based on the minimum distance travelled between two consecutive locations, adult brook charr were more active at dusk and at night than during the day. During daylight periods, individual fish displayed strong site selection, remaining in the same area along the shore from day to day. The fish left their inshore position at dusk, were highly mobile during the night, and returned to their focal point at sunrise, exhibiting diel homing behaviour. These results are supported by an increase in gillnet captures of adult brook charr in Lac Melchior at night. Data obtained by gillnet fishing in lakes Bondi and Simpson showed that juvenile (1+) brook charr were active throughout the diel cycle and that young-of-the-year were active mainly during the day, suggesting that there is an ontogenetic change in the diel activity of brook charr. Despite its limitations (restrictions on the number and size of tracked individuals, post-manipulation mortality, lifetime of transmitter battery), radiotelemetry allows for collection of multiple behavioural observations (distances travelled, instantaneous activity, site selection and homing) during the activity cycle of individual fish, and thus provides a finer degree of spatial resolution than alternative methods such as gillnetting.     

Foraging location and range of White-chinned Petrels Procellaria aequinoctialis breeding in the South Atlantic

The foraging range and principal feeding areas of White‐chinned Petrels breeding at South Georgia were determined using satellite telemetry. Foraging trips during incubation lasted 12–15 days and covered 3000–8000 km and 2–11 days and 1100–5900 km during chick‐rearing. Adults covered less distance per day during chick‐rearing (71 km) than during incubation (91 km) but the proportion covered at night (47%) was the same. Mean (31–34 km/h) and maximum (80 km/h) flight velocities were similar during both periods of the breeding season and during day and night. Between incubation shifts, White‐chinned Petrels travelled to the Patagonian shelf; during chick‐rearing they foraged more extensively. Most locations were between 30° to 55°W and 52° to 60°W around South Georgia/Shag Rocks and south to the South Orkney Islands. Diet samples from known foraging locations suggested birds fed mainly on krill and squid. They caught the squid Brachioteuthis? picta and Galiteuthis glacialis around Shag Rocks/South Georgia and also at sites close to the South Orkney Islands; Illex argentinus on the Patagonian shelf. Dispersal of adults after breeding failure was south to the South Orkney Islands then west to the Falkland Islands. This study confirms that breeding White‐chinned Petrels are amongst the widest‐ranging of seabirds; they may minimise competition with other Procellariiformes in the South Atlantic by their more extensive foraging range. The nature and extent of their range also brings substantial risk of high mortality rate in South Atlantic long‐line fisheries.