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PubMed2006

Notes on the biology of Trypoxylon (Trypargilum) opacum Brèthes (Hymenoptera; Crabronidae) in Southern Brazil.

The present study investigated the abundance, seasonality and various life-history traits of Trypoxylon (Trypargilum) opacum. Using trap-nests, 320 nests of T. opacum were collected in the Parque Municipal das Araucárias in Southern Brazil (25 degrees 23' 36" S and 51 degrees 27' 19" W) over a 3 year period. Nesting was more frequent during the warm season. Nests consisted of a linear series of 1 to 8 brood cells separated by mud partitions, usually followed by an empty vestibular cell and final-closure mud plug. Brood cells were most commonly provisioned with spiders of the family Araneidae. Sex-ratio was strongly female biased, 3.4:1 females:males. Natural enemies attacking nests T. opacum included chrysidids, ichneumonids, sarcophagids, bombyliids and ants.

Animals↗
PubMed2006

Nesting biology of Trypoxylon (Trypargilum) lactitarse Saussure (Hymenoptera, Crabronidae) in trap-nests in Southern Brazil.

This study was carried in the Parque Municipal das Araucárias in the municipality of Guarapuava, state of Paraná, Southern Brazil. Three hundred and sixty five nests of T. lactitarse were obtained using trap-nests of 0.7, 1.0, and 1.3 cm in diameter. All of them had similar architecture, regardless of the diameter of the trap-nest. Completed nests consisted of a linear series of brood cells whose average number per nest was of 3.3, 4.0 and 3.6 for the nests with 0.7 cm, 1.0 cm and 1.3 cm in diameter, respectively. They were constructed more often during the summer. T. lactitarse had two types of life cycles: direct development (without diapause), and delayed development (with diapause during winter). Natural enemies included Chrysididae, Sarcophagidae, Dolichopodidae and Ichneumonidae. Out of 1,353 identified spider prey, 1,313 belonged to the Araneidae family.

Animals↗
PubMed2006

Effects of three-dimensional and color patterns on nest location and progeny mortality in alfalfa leafcutting bee (Hymenoptera: Megachilidae).

ABSTRACT In alfalfa, Medicago sativa L., seed production where high bee densities are released, alfalfa leafcutting bee, Megachile rotundata (F.) (Hymenoptera: Megachilidae), females may enter several nesting holes before locating their nests. Such levels of "wrong hole" visits lead to an increase in the time spent by females locating their own nests, thereby decreasing alfalfa pollination efficiency and possibly healthy brood production. The objectives of this study were to determine the effect of different nesting board configurations in commercial alfalfa leafcutting bee shelters (separating nesting boards, applying a three-dimensional pattern to the boards, applying a color contrast pattern, or applying a combination of three-dimensional and color contrast patterns) on nest location performance, on the incidence of chalkbrood disease, and on the incidence of broodless provisions. Separating the nesting boards inside shelters improved the ability of females to locate their nests. An increase in nest location performance also occurred in boards with the three-dimensional pattern and the combined three-dimensional and color contrast pattern, compared with the uniform board (a standard configuration currently used commercially). The percentage of provisioned cells that were broodless was not statistically different between treatments, but the percentage of larvae infected with chalkbrood decreased by half in the three-dimensional board design, compared with the uniform board.

Animals↗
PubMed1975

Influence of oestrogen on the initiation of nesting behaviour in female budgerigars.

Intact, breeding female budgerigars enter and occupy a nestbox 8-10 days before egg-laying. Ovariectomized budgerigars did not enter nestboxes. Oestradiol-17 beta monobenzoate (OB) (0-05 mg, i.m.) induced ovariectomized birds to enter nestboxes. Higher dosages (0-1 or 0-5 mg) did not facilitate this effect. The amount of time spent in nesting behaviour by all OB-treated groups did not differ from that shown by a group of intact females during the initial phase of the nesting sequence (first 4 days in the nestbox), but was significantly less than that of intact females undergoing later stages of nesting behaviour (4 days before and after laying the first egg). Oestradiol induced a increase in oviduct weight and size which was dose-dependent. With a low dose (0-05 mg OB), the oviducts were slightly larger than those of intact females which had been in the nestbox 1-2 days. With higher dose levels (0-1-0-5 mg OB), precursor albumen granules had formed in tubular glands of the magnum, a stage more typical of females which had been in the nestbox 4-6 days. The results indicate that low levels of oestrogen induce female budgerigars to enter nestboxes and initiate oviduct development. Subsequent phases of the nesting behaviour and oviduct development may be causally related to other hormones.

Animals↗
PubMed1975

The role of short days in the termination of photorefractoriness in female canaries (Serinus canarius).

Photorefractory intact female canaries were exposed to a photoperiod of 8 h light: 16 h darkness (8L: 16D) for 0, 2, 4 or 6 weeks before photostimulation with 14L: 10D for 4 weeks. Photoresponsiveness was measured in terms of plasma immunoreactive LH, ovary and oviduct weights, follicle size and nest-building behaviour. Birds not exposed to 8L: 16D were unresponsive to photostimulation while those exposed for 6 weeks to 8L: 16D were as fully photosensitive as females similarly treated immediately before their first breeding season. Birds exposed for 2 or 4 weeks to 8L: 16D responded to subsequent photostimulation but were not as responsive as birds exposed to short days for 6 weeks. Positive correlations between the two ovarian parameters and between these ovarian parameters and oviductal weight existed in all groups exposed to short days, but not in birds not exposed to short days. It is concluded that the restoration of photosensitivity at the end of the refractory period is a function of the number of short days experienced; about 6 weeks of short days are needed for its completion. In another experiment photorefractory birds exposed for 6 weeks to short days without subsequent photostimulation, although potentially photosensitive, were indistinguishable (in terms of the above parameters) from refractory birds kept on long days for the same period; in these birds refractoriness was not broken.

Animals↗
PubMed1975

Effects of ovarian steroids and prolactin on the sequential development of nesting behaviour in female budgerigars.

As intact, breeding female budgerigars approach egg-laying, they spend an increasing amount of time in the nestbox and nest hollow. The brood patch area begins to defeather and becomes vascular and the oviduct increases in weight. Precursory albumen forms in the tubular glands of the oviduct. Oestradiol (OB) treatment in combination with prolactin (OB+PL) induced ovariectomized budgerigars to display nesting behaviour which did not differ from that shown by intact females in the 3 days immediately preceding egg-laying. In contrast, OB induced only the initial phase of the nesting sequence and the effects of OB in combination with progesterone (OB+PR) were intermediate between treatments with OB alone and OB+PL. Incubation of artificial eggs occurred only in the OB+PL group and the latency to display of the incubation posture was shorter in the OB+PL group than in the OB+PR group. No incubation posture was displayed by the OB-treated group. Oviduct development was not influenced by prolactin, but progesterone induced precocious development of tubular glands in the magnum region of the oviduct. Treatment with OB+PR induced uniform development of precursor albumen in the tubular glands. Development of the brood patch occurred with both OB+PL and OB+PR treatment. However, OB+PR resulted in defeathering which was advanced in relation to vascularity when compared with intact breeding females, whereas defeathering and vascularity of the OB+PL group did not differ from that of intact females at egg-laying. These results indicate that prolactin in combination with oestradiol was more effective than progesterone not only in inducing the later phases of nesting behaviour but also in initiating incubation behaviour and defeathering of the brood patch area.

Abdomen↗
PubMed1976

Effect of a skeleton photoperiod on the daylength-dependent response to oestrogen in canaries (Serinus canarius).

Previous studies have shown that ovariectomized canaries, injected with 50 mug oestradiol benzoate thrice weekly, show more oestrogen-induced nest-building on a long day than on a short day. In this study the same effect was obtained with castrated canaries. The influence of time available for building was assessed first by comparing castrated males on skeleton long days with birds on short days, the total number of light hours being equal. More birds in the skeleton long-day group placed material in the nest, and did so with a shorter latency, than birds in the short-day group. Thus the differences between short- and long-day birds are unlikely to be due entirely to differences in the time available. However, some of the long-day birds were no more active than the short-day ones suggesting that the skeleton long-day schedule does impose some constraint. In a third experiment photorefractory females (whose ovaries do not secret oestrogen in response to long days) kept on a long skeleton-day scored similarly on all measures of building as birds kept on a full 14 h day and significantly more than birds on a short day. The results also indicate that the birds are measuring daylength by means of a diurnal rhythm of photosensitivity, an effect comparable to that of longer photoperiods on gonadal growth.

Animals↗
PubMed1981

Concentrations of prolactin and luteinizing hormone in plasma of doves in relation to incubation and development of the crop gland.

The concentrations of prolactin and LH were measured in the plasma of male and female ring doves (Streptopelia risoria) during the breeding cycle. Prolactin concentrations were low during courtship and early incubation but increased markedly (P less than 0.01 in both sexes) between days 7 and 15 of incubation, during the period of rapid growth of the crop sac. Levels remained raised for 4 days after the young had hatched but then declined as the crop sacs gradually regressed. These observations showed that concentrations of prolactin were high at the time when the crop sacs were proliferating and producing 'milk' for feeding the young, but that there was no increase in prolactin secretion at the onset of incubation as occurs in ducks, hens and other birds. In samples taken from doves at various times of the day and night there was no increase in plasma prolactin during the first few days of incubation. Concentrations of LH in plasma were generally higher in male doves than in females, but in both sexes were significantly higher during courtship than during incubation and brooding the young. Concentrations increased again when the young were independent and the parents began a second round of courtship.

Animals↗
PubMed1988

Relationships between prolactin, LH and broody behaviour in bantam hens.

The interactions between broody behaviour and changes in concentrations of plasma prolactin and LH were investigated in bantam hens. Adoption of newly hatched chicks caused incubating hens to leave their nests and prevented plasma prolactin decreasing as rapidly as in hens deprived of their nests and not given chicks. Further, the hens allowed to rear chicks came back into lay later (P less than 0.001) than the hens not allowed chicks. Plasma prolactin decreased and plasma LH increased in hens deprived of their nests: these changes were reversed when the hens re-nested. The changes in plasma LH and prolactin in nest-deprived and re-nesting birds were not always synchronous; this was particularly clear immediately after nest deprivation when the increase in plasma LH preceded the decrease in the plasma prolactin. Readiness to incubate disappeared between 48 and 72 h after nest deprivation and corresponded with the time when plasma prolactin decreased to baseline values. Administration of ovine prolactin depressed (P less than 0.01) the initial increase in plasma LH after nest deprivation, but repeated administration of prolactin for up to 72 h failed to suppress plasma LH to the values found in incubating hens. Repeated administration of ovine prolactin at 5- to 8-h intervals for 72 h maintained readiness to incubate in nest-deprived hens. It is concluded that the secretion of prolactin in broody hens is facilitated by the presence of chicks and that increased concentrations of plasma prolactin maintain incubation behaviour. In incubating hens the secretion of LH and prolactin may be partly regulated independently. In addition, LH secretion may also be inhibited by increased plasma prolactin.

Animals↗
PubMed2006

Costs of an immune challenge and terminal investment in a long-lived bird.

An induced immune challenge can have two counteracting effects on an individual's reproductive investment. (1) The resource demand could increase to "fuel" the immunologic reaction, which in turn can lead to an adaptive decrease in investment in resource-costly activities, such as reproduction. One the other hand, (2) the individual could assume that the immune activity it experiences is indicative of a serious infection. The latter can lead to an adaptive increase in reproductive investment in response to the reduced prospects of survival and future reproduction, so called "terminal investment." To measure such life-history-related consequences of increased immune activity, one group of incubating female Common Eiders (Somateria mollissima) was injected with a nonpathogenic antigen (sheep red blood cells, SRBC) while controls were injected with sterile saline. The eider is a long-lived sea-duck. Females, who incubate the eggs and care for young without assistance from the male, engage in facultative anorexia during incubation leading to a large reduction in body mass. Eiders can abandon their young to other females at the cost of reduced young survival. The immune challenge resulted in a larger mass loss, a prolonged incubation period, and reduced return rate, demonstrating both short- and long-term costs of immune challenge. Additionally, in response to what might have been interpreted as reduced survival chances in immune-challenged females, these females more often tended their own brood after hatching, despite having suffered higher costs during incubation.

Animals↗
PubMed2006

Songbird abundance and parasitism differ between urban and rural shrublands.

Many studies have examined differences in avian community composition between urban and rural habitats, but few, if any, have looked at nesting success of urban shrubland birds in a replicated fashion while controlling for habitat. We tested factors affecting nest survival, parasitism by the Brown-headed Cowbird (Molothrus ater), and species abundance in shrubland habitat in rural and urban landscapes. We found no support for our hypothesis that nest survival was lower in urban landscapes, but strong support for the hypothesis that survival increased with nest height. We found strong support for our hypothesis that cowbird parasitism was greater in urban than rural landscapes; parasitism in urban sites was at least twice that of rural sites. We found strong support for an urban landscape effect on abundance for several species; Northern Cardinal (Cardinalis cardinalis) and Brown-headed Cowbirds were more abundant in urban landscapes, whereas Field Sparrow (Spizella pusilla) and Blue-winged Warbler (Vermivora pinus) were more abundant in rural sites. There was support for lower abundances of Blue-gray Gnatcatcher (Polioptila caerulea) and Indigo Bunting (Passerina cyanea) with increased housing density. For six other species, edge and trail density or vegetation parameters best explained abundance. Lower abundances and greater parasitism in habitat patches in urban landscapes are evidence that, for some species, these urban landscapes do not fulfill the same role as comparable habitats in rural landscapes. Regional bird conservation planning and local habitat management in urban landscapes may need to consider these effects in efforts to sustain bird populations at regional and local scales.

Animals↗