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.

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.

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.

scholarly journals A difference between sexes: temporal variation in the diet of Carollia perspicillata (Chiroptera, Phyllostomidae) at the Macaregua cave, Santander (Colombia)

2020 ◽  
pp. 27-35
Author(s):  
A. Alviz ◽  
J. Pérez-Torres
Keyword(s):  
Time Series ◽  
Time Series Analysis ◽  
Breeding Season ◽  
Transition Period ◽  
Dietary Diversity ◽  
Foraging Strategies ◽  
Carollia Perspicillata ◽  
Series Analysis ◽  
Dietary Breadth ◽  
Males And Females

Organisms adjust their foraging strategies to optimize the energetic costs during foraging with respect to benefits gained. These strategies are usually different in males and females due to their specific requirements during reproduction. Knowing the temporal dietary composition and variation may help us understand how intrinsic factors can influence diet during the breeding season. Seba’s short–tailed fruit bat (Carollia perspicillata) plays an important role in seed dispersal throughout the Neotropics. Seasonal dietary changes related to resource availability have been documented but dietary differences between males and females have not been analyzed. We tested the hypothesis that dietary breadth increases and varies between males and females of Carollia perspicillata during the breeding season. We collected 295 fecal samples (from 236 males and 182 females) between June 2012 and April 2013 at the Macaregua cave (Santander, Colombia). Sex, diet and overlap were recorded. Time series analysis of dietary variation were estimated and related to food (fruits and flowers) availability. Males were found to include 18 seed morphospecies within their diet, while females included 16 seed morphospecies. Ficus, Vismia and Acacia were the most commonly consumed plant genera within the diet of both males and females. The time series analysis throughout the year indicated that males had greater dietary diversity than females. Dietary richness for males peaked multiple times, while dietary richness for females peaked only once during the transition period between pregnancy and lactation. We recorded significant sex differences in the value of importance of plants in the diet, evenness, and dominance of plant species consumed, as well as differential consumption over the seasons. Knowing the variations in the diet allows us to address the differences between the foraging strategies that females and males use in response to energy demands, movement patterns and habitat use. This is essential to understand all those processes that organisms must carry out for their survival and maintenance.

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.

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.

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.

scholarly journals Altitudinal movements and conservation of Bare-necked Umbrellabird Cephalopterus glabricollis of the Tilarán Mountains, Costa Rica

2003 ◽  
Vol 13 (1) ◽  
pp. 45-58 ◽  
Author(s):  
Johel Chaves-Campos ◽  
J. Edgardo Arévalo ◽  
Mariamalia Araya
Keyword(s):  
Costa Rica ◽  
Breeding Season ◽  
Protected Area ◽  
Radio Telemetry ◽  
Fruit Breeding ◽  
Potential Threat ◽  
Fruit Abundance ◽  
Transect Counts ◽  
Using Data ◽  
High Elevations

Bare-necked Umbrellabird Cephalopterus glabricollis is endemic to Costa Rica and western Panama. It eats fruit, breeding at high elevations (≥ 800 m) and migrating to lower elevations during the non-breeding season. Using data from transect counts and radio-telemetry, we monitored bird movements in a protected area (Monteverde–Arenal–San Ramón reserves) in the Tilarán Mountains, Costa Rica. We also monitored fruit abundance along an altitudinal gradient to explore the potential relationship between bird movements and the abundance of the fruits this species consumed. The presence and abundance of umbrellabirds at high elevations (1,400 m) during the breeding season (March–June) coincided with the highest peak of fruit abundance. The presence of umbrellabirds in the lowlands (400 m) during the non-breeding season overlapped with the period of highest fruit abundance at these elevations. At middle elevations, bird presence and abundance did not correlate with fruit abundance. Radio-tagged birds left the protected area during the non-breeding season and there were no umbrellabirds inside the protected area during this period. Habitats where this species bred were well represented in the protected area but the habitat where they spent the non-breeding season was poorly represented, and was not adequately protected. This represents a potential threat to this species in the Tilarán Mountains.

scholarly journals Trends in mortality from ill-defined causes among the elderly in Brazil, 1979-2013: ecological study

2016 ◽  
Vol 134 (5) ◽  
pp. 437-445 ◽  
Author(s):  
Davi Félix Martins Junior ◽  
Ridalva Dias Martins Felzemburg ◽  
Acácia Batista Dias ◽  
Tania Maria Costa ◽  
Pedro Nascimento Prates Santos
Keyword(s):  
Ecological Study ◽  
Temporal Trend ◽  
Health Indicators ◽  
The Elderly ◽  
Simple Linear Regression ◽  
Geographical Regions ◽  
Proportional Mortality ◽  
Males And Females ◽  
Using Data ◽  
Health Situation

ABSTRACT CONTEXT AND OBJECTIVE: Mortality measurements are traditionally used as health indicators and are useful in describing a population's health situation through reporting injuries that lead to death. The aim here was to analyze the temporal trend of proportional mortality from ill-defined causes (IDCs) among the elderly in Brazil from 1979 to 2013. DESIGN AND SETTING: Ecological study using data from the Mortality Information System of the Brazilian Ministry of Health. METHODS: The proportional mortality from IDCs among the elderly was calculated for each year of the study series (1979 to 2013) in Brazil, and the data were disaggregated according to sex and to the five geographical regions and states. To analyze time trends, simple linear regression coefficients were calculated. RESULTS: During the study period, there were 2,646,194 deaths from IDCs among the elderly, with a decreasing trend (ß -0.545; confidence interval, CI: -0.616 to -0.475; P < 0.000) for both males and females. This reduction was also observed in the macroregions and states, except for Amapá. The states in the northeastern region reported an average reduction of 80%. CONCLUSIONS: Mortality from IDCs among the elderly has decreased continuously since 1985, but at different rates among the different regions and states. Actions aimed at improving data records on death certificates need to be strengthened in order to continue the trend observed.

Age, stucture, growth rates and movements of sea mullet, Mugil cephalus L., and Yellow-eye Mullet, Aldrichetta forsteri (Valenciennes), in the Swan-Avon river system, Western Australia

1981 ◽  
Vol 32 (4) ◽  
pp. 605 ◽  
Author(s):  
CF Chubb ◽  
IC Potter ◽  
CJ Grant ◽  
RCJ Lenanton ◽  
J Wallace
Keyword(s):  
Growth Rates ◽  
River System ◽  
First Year ◽  
Length Frequency ◽  
Frequency Distributions ◽  
Using Data ◽  
The Times ◽  
First Year Of Life ◽  
Breeding Seasons ◽  
System 1

The age structure, growth rates and movements of M. cephalus and A forsteri in the Swan-Avon river system have been investigated using data obtained from beach seining and gill netting carried out between February 1977 and June 1980. Length-frequency data and scale readings show that the populations of both species consist predominantly of 0+ and 1 + fish. From the times when the smallest fry (20-30 mm) were present in the lower part of the river system, and from the condition of the gonads of older fish, the breeding seasons of the sea and yellow-eye mullets have been estimated as extending from March to September and from March to August respectively. The bimodality or polymodality exhibited by the length-frequency distributions for the 0 + year classes suggest that in both species groups of individuals spawn at slightly different times. The range of mean total lengths and weights of animals caught in May near the end of the first year of life was 178-222 mm and 64-119 gin M. cephalus and 136-154 mm and 19-30 g in A. forsteri, which shows that the growth of each of these two species of mullet is relatively very rapid in the Swan-Avon river system. 1 + and 2 + fish tend to leave the estuary for varying periods. Although 0+ fish of both species utilized the shallow banks of the estuary throughout the year. the sea mullet moved further upstream and were not as consistently abundant in the lower estuary. Since 0+ yellow-eye mullet 40-100 mm long were also abundant in marine coastal waters between January and May. and sea mullet of comparable age were rarely observed in these regions, it would appear that M. cephalus is the more estuarine-dependent of the two species. Commercial catches of M. cephalus were greater than those of A. forsteri. This feature can be related in part to the much faster growth rate of M. cephalus, which results in a larger proportion of its youngest year classes reaching the minimum legal size for capture prior to the time when they leave the estuary in large numbers.

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