Ecology of Red-winged Blackbird parasitism by haematozoa

1991 ◽  
Vol 69 (9) ◽  
pp. 2352-2359 ◽  
Author(s):  
Patrick J. Weatherhead ◽  
Gordon F. Bennett
Keyword(s):  
Sexual Selection ◽  
Breeding Season ◽  
Parasite Prevalence ◽  
Agelaius Phoeniceus ◽  
Older Individuals ◽  
Parasite Resistance ◽  
Blood Samples ◽  
Prevalence Estimates ◽  
Males And Females ◽  
Breeding Seasons

We sampled haematozoa in Red-winged Blackbirds (Agelaius phoeniceus) over three consecutive breeding seasons in eastern Ontario to identify factors that affect the reliability of quantifying parasites as this pertains to testing Hamilton and Zuk's hypothesis of sexual selection. Parasite prevalence and intensity varied seasonally, indicating that for samples to be reliable they should not be taken either early or late in the breeding season, and analysis should be limited to prevalence (presence versus absence). Among males (but not females), parasite prevalence increased with age, indicating that all individuals are not exposed to parasites early in life, and therefore tests of the "parasite" hypothesis of sexual selection are best restricted to older individuals. Resampling of known individuals within and between years showed that some individuals changed from positive to negative. Prevalence estimates also varied by year, indicating that reliable estimates of prevalence for a species, necessary for interspecific tests of the parasite hypothesis, will require extensive sampling. Overall, parasite prevalence did not vary with habitat. Parasites were detectable in only 1 of 119 nestlings sampled, indicating either lack of exposure or inadequate time for infections to reach detectable intensities. In either case, it is not possible to test the assumption that parasite resistance is heritable using blood samples from nestlings. Although males and females were parasitized by the same array of parasites, the distribution of specific parasites differed significantly (males were more heavily parasitized by leucocytozoids). If males and females generally differ in either exposure or resistance to specific parasites, the coevolutionary dynamics between host and parasite and the implications for sexual selection will require reassessment.

2. Mating systems, or who goes with whom, and for how long

2018 ◽  
pp. 16-33
Author(s):  
Leigh W. Simmons
Keyword(s):  
Sexual Selection ◽  
Mating System ◽  
Social Relationships ◽  
Breeding Season ◽  
Mating Systems ◽  
Practical Applications ◽  
Multiple Partners ◽  
Monogamous Species ◽  
Genetic Techniques ◽  
Males And Females

‘Mating systems, or who goes with whom, and for how long’ examines the variation in how males and females associate during the breeding season, ranging from brief couplings with multiple partners to lifelong monogamy. It also shows how the discovery that females mate with many partners, even in supposedly monogamous species such as songbirds, was made possible by modern genetic techniques. Variation in mating systems holds considerable implications for the operation of sexual selection. The way that animal mating systems have been explained historically is outlined before considering how a more contemporary understanding of genetic and social relationships has reshaped our thinking and how understanding a species’ mating system can have practical applications.

Reproduction of Pseudomys novaehollandiae (Muridae) in the Wild

1980 ◽  
Vol 7 (3) ◽  
pp. 385 ◽  
Author(s):  
CM Kemper
Keyword(s):  
Breeding Season ◽  
New South ◽  
Reproductive Organs ◽  
First Year ◽  
Reproductive Condition ◽  
South Wales ◽  
In The Wild ◽  
Males And Females ◽  
Preputial Glands ◽  
Breeding Seasons

A total of 291 P. novaehollandiae were observed during a 4-y study in the Nelson Bay and Smith Lake regions of New South Wales. Reproductive organs were examined from males and females, May 1972-May 1974; reproductive condition of females was noted during a CMR study, August 1974-July 1976. Breeding seasons (conceptions and births) occurred between August and early January (4-5 months) in the first 3 years and between September and March (7 months) in the last year. Second-year females produced three or four litters in short seasons, four or five litters in the long season and up to 20 offspring per season. First-year females produced one litter in short seasons and one or two litters in the long season. Mean litter size was 4.56 (2-6). Ovarian follicles were largest in September and smallest in May. Small, inactive CL persisted in parous females until May. Placental scars were present in all sampled months. Vaginae remained closed during the non-breeding season. In mature males testes and epididymides contained sperm from July to March. Vesicular, prostate and preputial glands were enlarged and secretory from September to December. Testes were smallest and least developed in May and June. Males were divided into five categories depending on age and overall reproductive condition. Sexual maturity was reached in the breeding season of birth by some males (33%) and females (13-88%). More females matured early when population density was low. Food abundance and quality may have been important variables in regulating the timing of the breeding season.

A test of the condition-bias hypothesis using Brown-headed Cowbirds trapped during the breeding season

1991 ◽  
Vol 69 (10) ◽  
pp. 2686-2692 ◽  
Author(s):  
Kevin W. Dufour ◽  
Patrick J. Weatherhead
Keyword(s):  
Breeding Season ◽  
Molothrus Ater ◽  
Foraging Strategies ◽  
Feeding Response ◽  
Poor Condition ◽  
Males And Females ◽  
Using Data ◽  
Breeding Seasons ◽  
Mist Net ◽  
Trap Bias

We examined trap bias relative to body condition, age, and sex using data collected from Brown-headed Cowbirds (Molothrus ater) decoy trapped during the 1987 and 1988 breeding seasons. A condition bias was evident, as decoy-trapped birds were in poor condition relative to those caught by mist net in an adjacent roost. This occurred in both sexes and independently of study year and male age. Paradoxically, however, males in better condition when first trapped were more likely to be recaptured in the same season, possibly reflecting more widespread movement, and hence fewer encounters with traps, by birds in poor condition. Hatching-year birds were more likely than adults to be recaptured in the same season. Trapped samples were strongly male biased, which probably reflects a difference in nutritional requirements, and thus foraging strategies, between males and females during the breeding season. This study indicates that biases among birds trapped by methods that rely on a feeding response are likely to be widespread and difficult to predict, suggesting that interpretation of data from such samples always requires caution.

The testis is not the major source of circulating follistatin in the ram

1996 ◽  
Vol 149 (1) ◽  
pp. 55-63 ◽  
Author(s):  
A J Tilbrook ◽  
D M de Kretser ◽  
F R Dunshea ◽  
R Klein ◽  
D M Robertson ◽  
...  
Keyword(s):  
Breeding Season ◽  
Jugular Vein ◽  
Plasma Concentrations ◽  
Testicular Tissue ◽  
Blood Samples ◽  
Gonadotrophin Releasing Hormone ◽  
Physiological Dose ◽  
Significant Uptake ◽  
Breeding Seasons ◽  
Matched Samples

Abstract The aims of this study were to determine the plasma concentrations of follistatin in rams and to assess if the testis contributes to circulating follistatin and if there is uptake or production of follistatin by the head in rams. Catheters were inserted in the carotid artery, jugular vein and spermatic vein of intact rams during the non-breeding season (experiment 1; n=5) and breeding season (experiment 2; n=4). In experiment 1, blood samples were collected from 5 rams every 10 min for 4 h, commencing 20–60 min after surgery. After 2 h of sampling 1 μg gonadotrophin-releasing hormone (GnRH) was injected intravenously. In experiment 2, blood samples were collected from 4 of the rams used in experiment 1 by venipuncture 30 and 15 min before surgery and every 15 min throughout surgery. Commencing 1 h after surgery, matched samples were taken from each of the vessels every 10 min for 4 h (1–4 h after surgery), then every hour for 20 h (4–24 h after surgery) and then every 10 min for 4 h (24–28 h after surgery). In both experiments, follistatin secretion was non-pulsatile and there were no significant differences between the concentrations of follistatin in any of the vessels. There was a significant (P<0·05) increase in the concentrations of follistatin in each of the vessels throughout the 4 h of 10-min sampling in both experiments. In experiment 2 plasma concentrations of follistatin in the jugular vein were significantly (P<0·05) lower before surgery than at other stages of the experiment. During the non-breeding season (experiment 1) the concentrations of follistatin in all vessels were about 2-fold higher (P<0·001) than during the breeding season (experiment 2). Concentrations of follistatin were measured in the testicular tissue of the ram, bull, monkey and rat and were found to be 13·6, 2·1, 2·5, 0·8 ng/g testis respectively. In experiment 3, blood samples were collected every 15 min for 4 h from castrated rams (n=6) in the absence of treatment with testosterone propionate (TP) and after 7 days of treatment with a physiological dose of TP during the breeding and non-breeding seasons. There was no effect of stage of breeding season or TP on the plasma concentrations of follistatin and these concentrations in the castrated rams were similar to the concentrations in the intact rams in experiment 2. In experiment 4, the function of Leydig cells was stimulated by administration of human chorionic gonadotrophin but this had no effect on plasma concentrations of follistatin. These experiments show that the concentrations of follistatin in the plasma of rams are measurable, that the testis is not the major contributor to circulating follistatin and that there is no significant uptake or production of follistatin by the head in rams. It appears that the contribution of the testis to circulating follistatin may vary with the stage of the breeding season, being greater during the non-breeding season than the breeding season. The gonadotrophins and testosterone do not appear to have a direct effect on the secretion of follistatin in rams. The increase in concentrations of circulating follistatin during surgery and more frequent blood sampling suggest a stress-related effect on the production of follistatin. Journal of Endocrinology (1996) 149, 55–63

Population ecology of the Australian frog Crinia signifera: adults and juveniles

1996 ◽  
Vol 23 (3) ◽  
pp. 249 ◽  
Author(s):  
CM Bull ◽  
I Williamson
Keyword(s):  
Breeding Season ◽  
Population Ecology ◽  
South Australia ◽  
Adult Mortality ◽  
Large Size ◽  
Early Emergence ◽  
The Common ◽  
Males And Females ◽  
A Site ◽  
Breeding Seasons

A population of the common Australian frog Crinia signifera Girard, 1853 was studied over a 3.5 year period at a site near Bridgewater in South Australia. In this population, C. signifera are long lived and iteroparous, with some individual males and females participating in at least four consecutive breeding seasons. Adult survivorship was high (up to about 70% per annum) for both males and females. Metamorphosis occurred from October to January and some individuals reached maturity within a year. However, most individuals reached maturity in the second breeding season following metamorphosis. Survival of juveniles ranged from 5 to 72% per annum, with individuals emerging early having higher survival than those that metamorphosed late. However, it was not clear whether increased survival was associated with early emergence or large size at emergence. The data support the argument that iteroparity is favoured in situations in which preadult mortality is higher and less predictable than adult mortality.

scholarly journals Seasonal changes in the negative feedback regulation of the secretion of the gonadotrophins by testosterone and inhibin in rams

1999 ◽  
Vol 160 (1) ◽  
pp. 155-167 ◽  
Author(s):  
AJ Tilbrook ◽  
DM de Kretser ◽  
IJ Clarke
Keyword(s):  
Breeding Season ◽  
Negative Feedback ◽  
Plasma Concentrations ◽  
Feedback Regulation ◽  
Negative Feedback Regulation ◽  
Blood Samples ◽  
Vehicle Treatment ◽  
Breeding Seasons ◽  
Lh Secretion ◽  
Hypothalamic Level

Three experiments were conducted with castrated Romney Marsh rams (wethers) to investigate the ability of testosterone and inhibin to suppress the secretion of LH and FSH during the breeding and the non-breeding seasons. In Experiment 1, wethers (n=5/group) were treated every 12 h for 7 days with oil or 16 mg testosterone propionate (i.m.) and were then given two i.v. injections either of vehicle or of 0.64 microg/kg human recombinant inhibin A (hr-inhibin) 6 h apart. Blood samples were collected for 4 h before inhibin or vehicle treatment and for 6 h afterwards for the assay of LH and FSH. In Experiments 2 and 3 wethers underwent hypothalamo-pituitary disconnection (HPD) and were given 125 ng GnRH i.v. every 2 h. In Experiment 2, HPD wethers (n=3/group) were injected (i.m.) every 12 h with oil or testosterone and blood samples were collected over 9 h before treatment and 7 days after treatment. In Experiment 3, HPD (n=5/group) wethers were treated with vehicle or hr-inhibin, as in Experiment 1, after treatment with oil, or 4, 8 or 16 mg testosterone twice daily for 7 days. Blood samples were collected over 4 h before treatment with vehicle or hr-inhibin and for 6 h afterwards. Treatment of wethers with testosterone (Experiment 1) resulted in a significant decrease in the plasma concentrations of LH and number of LH pulses per hour but the magnitude of these reductions did not differ between seasons. Testosterone treatment had no effect on LH secretion in GnRH-pulsed HPD wethers in either season and treatment with hr-inhibin did not affect LH secretion in wethers or HPD wethers in any instance. Plasma concentrations of FSH were significantly (P<0.05) reduced following treatment with testosterone alone during the breeding season but not during the non-breeding season. FSH levels were reduced to a greater extent by treatment with hr-inhibin but this effect was not influenced by season. During the non-breeding season, the effect of hr-inhibin to suppress FSH secretion was enhanced in the presence of testosterone. These experiments demonstrate that the negative feedback actions of testosterone on the secretion of LH in this breed of rams occurs at the hypothalamic level and is not influenced by season. In contrast, both testosterone and inhibin act on the pituitary gland to suppress the secretion of FSH and these responses are affected by season. Testosterone and inhibin synergize at the pituitary to regulate FSH secretion during the non-breeding season but not during the breeding season.

Observation on the breeding biology of Polypedates teraiensis (Dubois, 1987) (Amphibia: Rhacophoridae)

2017 ◽  
Vol 17 (1) ◽  
pp. 25-32
Author(s):  
Jacinta Lalchhanhimi ◽  
Lalremsanga H.T.
Keyword(s):  
Sexual Dimorphism ◽  
Breeding Season ◽  
Sound Production ◽  
Reproductive Function ◽  
Breeding Biology ◽  
Tree Frog ◽  
University Campus ◽  
Morphometric Measurements ◽  
Advertisement Calls ◽  
Males And Females

The breeding biology of tree frog, Polypedates teraiensis was studied during the breeding season at Mizoram University Campus. It was found that sound production by male during the breeding season was primarily a reproductive function and advertisement calls attract females to the breeding areas and announce other males that a given territory is occupied. The aim of this study was to provide the detailed information on the breeding behaviour and the advertisement calls of Polypedates teraiensis. The morphometric measurements of the amplecting pairs (males and females) for sexual dimorphism along with clutch sizes were also studied.

Reproductive behavior

2018 ◽  
Author(s):  
Rachel Olzer ◽  
Rebecca L. Ehrlich ◽  
Justa L. Heinen-Kay ◽  
Jessie Tanner ◽  
Marlene Zuk
Keyword(s):  
Sexual Selection ◽  
Sexual Conflict ◽  
Female Choice ◽  
Reproductive Behavior ◽  
Mating Systems ◽  
Insect Behavior ◽  
Sequential Approach ◽  
Evolutionary Mechanisms ◽  
Anatomy And Physiology ◽  
Males And Females

Sex and reproduction lie at the heart of studies of insect behavior. We begin by providing a brief overview of insect anatomy and physiology, followed by an introduction to the overarching themes of parental investment, sexual selection, and mating systems. We then take a sequential approach to illustrate the diversity of phenomena and concepts behind insect reproductive behavior from pre-copulatory mate signalling through copulatory sperm transfer, mating positions, and sexual conflict, to post-copulatory sperm competition, and cryptic female choice. We provide an overview of the evolutionary mechanisms driving reproductive behavior. These events are linked by the economic defendability of mates or resources, and how these are allocated in each sex. Under the framework of economic defendability, the reader can better understand how sexual antagonistic behaviors arise as the result of competing optimal fitness strategies between males and females.

scholarly journals Evidence for use of both capital and income breeding strategies in the mangrove tree crab, Aratus pisonii

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jade Carver ◽  
Morgan Meidell ◽  
Zachary J. Cannizzo ◽  
Blaine D. Griffen
Keyword(s):  
Breeding Season ◽  
Breeding Strategy ◽  
Reproductive Period ◽  
Breeding Strategies ◽  
Mangrove Tree ◽  
Income Breeding ◽  
Aratus Pisonii ◽  
Breeding Seasons ◽  
And Storage ◽  
Capital And Income Breeding

AbstractTwo common strategies organisms use to finance reproduction are capital breeding (using energy stored prior to reproduction) and income breeding (using energy gathered during the reproductive period). Understanding which of these two strategies a species uses can help in predicting its population dynamics and how it will respond to environmental change. Brachyuran crabs have historically been considered capital breeders as a group, but recent evidence has challenged this assumption. Here, we focus on the mangrove tree crab, Aratus pisonii, and examine its breeding strategy on the Atlantic Florida coast. We collected crabs during and after their breeding season (March–October) and dissected them to discern how energy was stored and utilized for reproduction. We found patterns of reproduction and energy storage that are consistent with both the use of stored energy (capital) and energy acquired (income) during the breeding season. We also found that energy acquisition and storage patterns that supported reproduction were influenced by unequal tidal patterns associated with the syzygy tide inequality cycle. Contrary to previous assumptions for crabs, we suggest that species of crab that produce multiple clutches of eggs during long breeding seasons (many tropical and subtropical species) may commonly use income breeding strategies.

The effects of moonlight on nocturnal activity in bushy-tailed wood rats (Neotoma cinerea)

1999 ◽  
Vol 77 (3) ◽  
pp. 480-485 ◽  
Author(s):  
Michael G Topping ◽  
John S Millar ◽  
James A Goddard
Keyword(s):  
Light Level ◽  
Intermediate Level ◽  
Nocturnal Activity ◽  
Risk Of Predation ◽  
Increased Risk ◽  
Neotoma Cinerea ◽  
Two Measures ◽  
Males And Females ◽  
Rocky Outcrops ◽  
Breeding Seasons

The nocturnal activity of bushy-tailed wood rats (Neotoma cinerea) was monitored for two breeding seasons (1993 and 1994) in the Canadian Rockies. Radiotelemetry was used under three levels of moonlight to assess two measures of nocturnal activity: (i) the proportion of animals crossing rocky outcrops and entering the surrounding forest to forage, search for mates, or both, and (ii) the distance moved from the den site while in the forest. Males and females exhibited significant differences among moonlight levels, with greater activity on nights of intermediate-level moonlight and less activity on nights with bright or dark moonlight. There was no difference in the proportions of males and females active at any moonlight level. The distances moved from the den did not differ among moonlight levels for either males or females. Having traversed the rocks and entered the forest, individuals moved similar distances regardless of light level. These results suggest that wood rats respond to moonlight only when making the decision to cross rocks and enter the forest. This behaviour presumably serves to counteract the increased risk of predation on bright nights.

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