Nest defence by song sparrows: methodological and life history considerations

Summary Several aspects of nest defence behavior were investigated in song sparrows (Melospiza melodia) in eastern Ontario. Two independent tests were made of the hypothesis that the increase in nest defence observed through a nesting attempt is due to the birds becoming familiar with the nest threat, rather than because the nest contents increase in value to the parents. Neither test supported the hypothesis. As predicted by life history theory for species with age-independent mortality, males did not defend their nest more vigorously as they become older. Parents defended their nests less vigorously through the breeding season, contrary to the expected pattern of increased nest defence in response to declining renesting potential. This result may be attributable to a decline in offspring value through the breeding season. Nest defence behavior of mated individuals was positively correlated, independent of factors such as offspring age, renesting potential and brood size. From this result it is proposed that a source of variation in nest defence behavior may be individuals basing their own response on their mate's response in a positive feedback fashion. Males defended nests less vigorously than females, consistent with the expectation that males have lower certainty of parentage in the offspring. It is proposed that variation in paternal uncertainty could contribute to the unexplained variation reported in nest defence studies.     

Reproductive cycle of the chiton Chiton iatricus and environmental control of its gonad growth

The annual reproductive cycle of the chiton Chiton iatricus was studied for the period from September, 1977 to December, 1978. Gametogenesis is initiated in the November – December period followed by rapid gonadal growth up to March. Breeding season of C. iatricus extends up to the beginning of August. Though the emission of the gametes halts in August, the gonad never enters into the quiescent phase owing to the time required for the gametogensis. The examination of correlation between the reproductive events during the annual reproductive cycle and existing environmental factors suggests that multiple environmental factors are involved in the control of different phases of gonad growth. The collected data are discussed in the light of the reproductive physiology of C. iatricus.     

Role of Genetic Background in the Success of Reintroduced Peregrine Falcons

Abstract: Peregrine Falcons (    Falco peregrinus ) of seven subspecies from four continents were bred in captivity, and approximately 1173 of their progeny were released in the midwestern United States and adjacent regions of Ontario and Manitoba in an attempt to replace the original population that was extirpated by chlorinated hydrocarbon poisoning in the 1950s. We analyzed the success of individuals of the different subspecies introduced to the Midwest. Five of the seven subspecies released have contributed to the current breeding population. Subspecies of breeding Peregrine Falcons were equally represented when breeding birds of high productivity were compared with less prolific breeders. The subspecific makeup of the breeding population did not differ significantly from that of the released population, suggesting that adaptability in this species was sufficient to override genetic differences between subspecies. Peregrines of widely different genetic stocks have thrived after release, making substantial genetic contributions to the new population.     

Distribution,habitat preferences and behaviour of the critically endangered Maltese top-shell <Emphasis Type="Italic">Gibbula nivosa</Emphasis> (Gastropoda: Trochidae)

The Maltese top-shell, Gibbula nivosa Adams 1851, is a critically endangered marine trochid gastropod endemic to the Maltese Islands (central Mediterranean). Previously unrecorded live since 1981, rediscovery of this species in 2006 has enabled the collection of basic biological data for the first time, based on a population in Sliema Creek. The field distribution and habitat preferences of G. nivosa were investigated via stratified random sampling, while aspects of its behaviour were studied through laboratory experiments. Gibbula nivosa occurred primarily in near-homogeneous or homogeneous infralittoral cobble/pebble beds, at an overall density of 17.6 ± 25.0 SD individuals m⁻²; however, large spatial and temporal variations in abundance were recorded. The snails did not exhibit gregarious behaviour and the slightly clumped dispersion pattern noted in the field appeared to result from patchiness of the habitat. Recruitment was observed in post-summer months, which, together with data on shell-size distributions, suggests that G. nivosa spawns in early summer and attains adult size (maximum shell width ~9 mm) in less than 1 year. Gibbula nivosa showed a circadian activity pattern with nocturnal foraging involving indiscriminate ingestion of particles browsed off the substratum; observations on responses to four potential predators suggest that nocturnal activity may have evolved in response to diurnal predation. Historical records of snail occurrence and the present study suggest that population declines of G. nivosa in the past were probably related to habitat alteration as a result of anthropogenic pressure.     

Energetic cost of development through metamorphosis for the seastar<Emphasis Type="Italic"> Mediaster aequalis</Emphasis> (Stimpson)

Rates of oxygen consumption were measured for embryos, larvae and juveniles of the seastar Mediaster aequalis for 76 days post-fertilization. The rate increased from 0.65 nmol O₂ ind^–1 h^–1 at 6 h after fertilization to 2.8 nmol O₂ ind^–1 h^–1 at day 35. Larvae became competent to metamorphose around day 35 post-fertilization and began to decrease their metabolic rate after this time. Metamorphosed juveniles consumed 0.74 nmol O₂ ind^–1 h^–1. Eggs contained 138.6 µg lipid ind^–1 and 12.1 µg protein ind^–1. Lipid levels decreased in concentration throughout development while protein levels increased slightly. The lipid levels decreased by 88.5 µg from eggs to day 76 larvae, accounting for 3.5 J of energy. Total oxygen consumption to this point was 3.74 µmol O₂ ind^–1, accounting for 1.84 J. The energetic demand up to day 76 was met completely through the use of lipid reserves. Metamorphosed juveniles expended 0.5 J more than larvae at the same age. Tubes of the polychaete Phyllochaetopterus prolifica were able to induce metamorphosis in M. aequalis larvae and a non-polar extract of these tubes also triggered metamorphosis. Larvae that are delayed to metamorphose can sustain their metabolic rate with lipid reserves for a limited, yet undetermined, period.Communicated by P.W. Sammarco, Chauvin     

Polychlorinated biphenyls in marine sediments from the southern North Sea and Scheldt estuary: a ten-year study of concentrations, patterns and trends

The paper reports the concentrations and patterns of CBs in sediments of the Belgian part of the southern North Sea and the Scheldt estuary for the period 1991-2001. The long-term analytical performance was well within the quality assurance boundaries set at the outset of the study and is consistent with the state of the art for this type of analysis. The CB concentrations (given as the median of the sum of IUPAC Nos 28, 52, 101, 118, 138, 153 and 180) vary between 0.1 microg kg(-1) and 50 microg kg(-1) dry weight in the total sediment and it could be demonstrated that CB patterns in the fine fraction of the sediment were closely similar throughout the investigated area. Isolation of the fine fraction (<63 microm) by sieving can be regarded as a physical normalisation to reduce the differences in sediment granulometric composition. It allows for a better understanding of CB distribution and patterns and improves the trend analysis. A significant downward trend could not be found at any of the stations, which suggests that CB levels have not been changing in the area of interest in the past decade.     

Conservation Genetics of the Endangered Isle Royale Gray Wolf

Abstract. The small group of wolves on Isle Royale has been studied for over three decades as a model of the relationship between large carnivores and their prey. During the last ten years the population declined from 50 individuals to as few as 12 individuals. The causes of this decline may be food shortages, disease, or reduced genetic variability. We address the issues of genetic variability and relationships of Isle Royale wolves using allozyme electrophoresis, mtDNA restriction-site analysis, and multilocus hypervariable minisatellite DNA analysis (genetic fingerprinting). Our results indicate that approximately 50% of the allozyme heterozygosity has been lost in the island population, a decline similar to that expected if no immigration had occurred from the mainland. The genetic fingerprinting data indicate that the seven sampled Isle Royale wolves are as similar as captive populations of siblings. Surprisingly, the Isle Royale wolves have an mDNA genotype that is very rare on the mainland, being found in only one of 144 mainland wolves ThFF suggests that the remaining Isle Royale wolves areprobably derived from a single female founder     

Long-term variability in the structure of subtidal benthic communities in Puget Sound,Washington, USA

Data on benthic infauna from 4 permanent stations in Puget Sound off Seattle, USA, collected during 1963–1964, 1967, and 1969, revealed considerable stability in numbers of species and specimens and in diversity within stations among sampling dates. The species composition of the faunal assemblages also remained rather constant during the period of investigation, but the relative dominance among the numerically important species varied somewhat. Biomass data did not differ significantly in 1964 and 1969, but the 1967 data were considerably lower at all stations.