Determinants of social dominance and inheritance of agonistic behavior in an island population of silvereyes,Zosterops lateralis

Summary We examined components of agonistic behavior and dominance in parents and offspring of silvereyes on Heron Island, Great Barrier Reef, to discover their determinants. The data were collected over four years on 1,235 juveniles and their parents. Of four behavioral characters used to compare juveniles and their parents, bill clattering was seen significantly more among young from female parents that exhibited bill clattering. The total absence of submissive behavior and the total absence of aggressive behavior were shown more often than not by young from dominant male parents and subordinate female parents, respectively. Young fledging early in the breeding season tended to be more dominant than those fledging late in the season. The number of brood-mates or the local nest density did not affect the dominance of young. Dominance status appears to be little affected by the performance of parents.     

Effect of near-bottom currents on detection of bait by the abyssal grenadier fishes Coryphaenoides spp., recorded in situ with a video camera on a free vehicle

Free vehicles carrying bait, video cameras and current meters were deployed at three sites in the abyssal North Pacific Ocean in 1983 and 1984 (at depths of 3 800, 4 400 and 5 800 m). From the recovered video recordings, we analyzed responses of the abyssal grenadier fishes Coryphaenoides spp. to the bait, and, from the recovered current meters, we determined the velocities of the nearbottom tidal currents. The grenadiers consistently arrived at the camera within minutes after it landed (7.5 to 41 min, N=9 deployments), but the times of the first arrivals tended to increase within increasing distance from shore (which was correlated with increasing depth). Faster responses occurred near times of peak, as opposed to slack, current velocities. Behavioral observations suggest that grenadiers primarily use olfaction in locating the bait, because 75% of early arrivals came from down-current. Those coming from up-current typically did not appear to sense the bait until arriving down-current from it. A wait rather than search strategy is proposed for the use of food falls by these deep-sea scavengers.     

Skeletal Sr content and density in Porites spp. in relation to environmental factors

The coral genus Porites was investigated to evaluate the use of skeletal strontium content as a recorder of seasonal and annual temperature oscillations. In the Hawaiian archipelago, the mean annual water temperature fluctuates by ±0.5C°, with seasonal temperature ranges of 4 to 8C°; the resolution of the Sr thermometer appears to be ±1.5C°. Of this error term, ±0.7C° is analytical, the remainder is biological. Corals from some locations yield temperatures which are consistently offset from the Sr vs temperature calibration line, suggesting genetic population differences. Analysis of cores collected in 1980 from Hawaiian Porites spp. showed no discernible long-term trends over a 100 yr period. Although absolute temperatures are poorly resolved, subannual oscillations in skeletal Sr values accurately reflect recorded seasonal temperature variations. The most useful application of the Sr thermometer is in deciphering the skeletal density band pattern. Subannual oscillations in Sr-temperature values when correlated with density values showed a consistent pattern. When the sections chosen for x-radiography closely followed the growth axis, an abrupt shift from minimum to maximum skeletal density was evident in September/October each year, followed by a gradual decrease in density. The density pattern, shown by microdensitometry, is independent of latitude or temperature range over the Hawaiian archipelago. The annual density shift coincides with high but declining water temperature and solar insolation. If low-density growth represents optimum calcification conditions, the density shift in Hawaiian Porites spp. reflects a change in conditions from optimal to suboptimal. Analyses of samples from other Indo-Pacific locations confirm the generality of this density pattern and suggest a complex relationship between density and environmental light and temperature.Hawaii Institute of Geophysics Contribution No. 1209; Hawaii Institute of Marine Biology Contribution No. 618     

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) and long (LFT, >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.     

Optimal pollution permit endowments in markets with endogenous emissions

In a permit market with endogenous emissions, both firms and citizens purchase permits. Presented here are static and dynamic models of pollution permit markets with endogenous emissions. The optimal permit endowments are characterized when the regulator faces uncertainty about damages and uncertainty about the severity of the citizens’ collective action problem. Due to the possibility of learning over time, the regulator issues a larger number of permits in the first period of the dynamic model than in the static model.     

Paternal care in the European starling,Sturnus vulgaris: nestling provisioning

The extent to which male birds in polygynous species with biparental care assist in nestling feeding often varies considerably between nests of different mating status. Both how much polygynous males assist and how they divide their effort between nests may have a profound effect on the evolution of mating systems. In this study we investigated how males in the facultatively polygynous European starling Sturnus vulgaris invested in their different nests. The amount of male assistance affected the quality of the offspring. Polygynous males invested as much as monogamous males, but divided their effort asymmetrically between nests, predominantly feeding nestlings of first-mated (primary) females. Although females partly compensated for loss of male assistance, total feeding frequency was lower at primary females’ nests than at monogamous females nests. Secondary females received even less assistance with nestling rearing, and the extent to which males assisted decreased with the length of the interval between the hatching of the primary and secondary clutches. These results are contrasted with those from a Belgian populations of starlings with a much more protracted breeding season and thus greater opportunities for males to attract additional mates during the nestling rearing period. The results show that both the “defence of male parental investment model” and the “asynchronous settlement model” have explanatory power, but that their validity depends on the potential length of the breeding season. Received: 21 July 1995/Accepted after revision: 13 July 1996     

Begging affects parental effort in the pied flycatcher, Ficedula hypoleuca

It has been suggested that nestlings use begging to increase their share of parental resources at the expense of current or future siblings. There is ample evidence that siblings compete over food with nestmates by begging, but only short-term effects of begging on parental provisioning rates have been shown. In this study, we use a new experimental design to demonstrate that pied flycatcher (Ficedula hypoleuca) nestlings that beg more are able to increase parental provisioning rates over the major part of the nestling period, thus potentially competing with future siblings. Parents were marked with microchips so that additional begging sounds could be played back when one of the parents visited the nest. By playing back begging sounds consistently at either male or female visits, a sex difference in provisioning rate that lasted for the major part of the nestling period was induced. If each parent independently adjusts its effort to the begging intensity of nestlings, begging may also be the proximate control mechanism for the sexual division of labour. Received: 24 January 1997 / Accepted after revision: 30 August 1997     

Adoption or infanticide: options of replacement males in the European starling

The behaviour of a male bird towards a potential mate and her clutch may depend both on his expected paternity and on the likelihood that she will produce a replacement clutch if he commits infanticide. In this study we evaluate the choices made by replacement male European starlings Sturnus vulgaris. By removing males before and during laying, we induced other males, mainly neighbours, to mate with the reproductively active females. When the original male was removed before laying, a new male adopted the subsequent clutch in 14 out of 15 cases. When ten females were widowed during their laying period, replacement males never adopted their clutches. The paternity of replacement males was a function of when they replaced the former male. When replacement occurred more than 3 days before egglaying, the new male fathered nearly all offspring; when it occurred the day before laying, the new male still fathered more than every second young. When the original male was removed during his mate’s laying period, in five out of ten cases a replacement male committed infanticide by throwing out the eggs, but this only occurred in one out of 15 cases when removal took place before laying. The evidence for infanticide actually being committed by the replacement male was circumstantial. Four out of six of the females affected by apparent infanticide produced replacement clutches in which the male presumably had higher paternity than in the original clutch. In all cases, the male adopted the replacement clutch. In five cases when the original male was removed during laying, the neighbours neither adopted the brood nor committed infanticide, although they sometimes were seen courting the widowed female and copulating with her. These cases occurred later during laying than those were males comitted infanticide. The time from infanticide to the laying of the replacement clutch tended to increase as infanticide was committed later in the laying sequence. We conclude that strategies of potential replacement males are influenced by their expected paternity in the current brood and the probability that the female will produce an early replacement clutch. Received: 10 March 1995 / Accepted after revision: 28 October 1995