Juvenile dispersal in Gray Jays: dominant brood member expels siblings from natal territory

1991 ◽  
Vol 69 (12) ◽  
pp. 2935-2945 ◽  
Author(s):  
Dan Strickland
Keyword(s):  
Sex Ratio ◽  
Weight Distribution ◽  
Brood Size ◽  
Food Storage ◽  
Brood Reduction ◽  
Juvenile Dispersal ◽  
Storage Season ◽  
Unrelated Pair ◽  
Gray Jays ◽  
Perisoreus Canadensis

Breeding pairs of Gray Jays (Perisoreus canadensis) in Quebec and Ontario were accompanied in the autumn significantly more often by one nonbreeder, and less often by none or two, than expected from initial brood size frequencies. Among the rare cases of two nonbreeders accompanying a pair, there was no evidence that both were from the same brood. These observations, and the fact that 30.6% of single nonbreeders closely associated with autumn pairs of known, same-year breeding history were unrelated to those adults, indicated the division of juvenile Gray Jays into "stayers," which remained with their parents at no more than one per pair, and "leavers," which left their natal territory and sometimes joined an unrelated pair. The weight distribution of 62 stayers indicated that about two-thirds were males. Leavers had a more equal sex ratio and showed a strong tendency to associate with failed breeders. Stayers apparently had much higher first-summer survival than leavers but no significant chance to inherit their natal territory. Gray Jay broods broke up in June, through intrabrood aggression, when the young were 55–65 days old. Stayers were the dominant juveniles that forced out the leavers. Partial June dispersal may function as a type of brood reduction that permits the dominant juvenile to have exclusive access to a parental subsidy of stored food that is reliably adequate for the survival of only one extra bird on the territory. The best models describing the origin and winter acquisition of such a subsidy postulate recovery of stored food by memory and require that the expulsion of subordinate siblings occur at the beginning of the food storage season. The models predict that food stored by Gray Jays in June survives in significant enough quantities to enhance winter survival.

Population dynamics of Stenothoe valida Dana, 1852 (Amphipoda, Stenothoidae) at Cheongsapo beach of Busan, Republic of Korea

Crustaceana ◽  
2021 ◽  
Vol 94 (4) ◽  
pp. 413-429
Author(s):  
Ye Ji Lee ◽  
Won Gyu Park
Keyword(s):  
Population Dynamics ◽  
Life History ◽  
Sex Ratio ◽  
Brood Size ◽  
Ovigerous Female ◽  
Seasonal Pattern ◽  
Recruitment Rate ◽  
Republic Of Korea ◽  
Female Size ◽  
History Of

Abstract The population dynamics of Stenothoe valida Dana, 1852 were studied at Cheongsapo beach of Busan, Republic of Korea, from March 2019 to March 2020. Sampling was conducted once a month at low tide during spring tides. Specimens were grouped by the cephalic length at 0.025 mm intervals, and classified into four categories: females, ovigerous females, males and juveniles. The sex ratio, defined as females : total males + females, exceeded 0.5 during most of the study period. Brood size was significantly coupled with ovigerous female size. Two to four cohorts appeared at each study period. New cohorts occurred at almost every sampling except in the samples Jun-2, and Nov-2. Life span was estimated at 1-2 months. The juvenile ratio, the ratio of ovigerous females, and the recruitment rate estimated by FiSAT were commonly high in summer and winter. The life history of S. valida was not coupled with water temperature, but had a strong seasonal pattern.

Erroneous choice and foregone gains in hoarding gray jays ( Perisoreus canadensis )

2000 ◽  
Vol 3 (3) ◽  
pp. 127-134 ◽  
Author(s):  
T. A. Waite ◽  
K. L. Field
Keyword(s):  
Gray Jays ◽  
Perisoreus Canadensis

scholarly journals Weight-carrying Ability and Caching Behavior of Gray Jays, Perisoreus canadensis: Adaptations to Boreal Winters

2005 ◽  
Vol 119 (1) ◽  
pp. 101 ◽  
Author(s):  
Lynn L. Rogers
Keyword(s):  
Body Weight ◽  
Boreal Forest ◽  
Corvus Corax ◽  
Gray Jays ◽  
Risk Of Predation ◽  
Perisoreus Canadensis ◽  
Flight Loads ◽  
Insect Activity ◽  
Weight Carrying ◽  
Ability And Willingness

During 16 August to 21 September 1984, I determined how Gray Jays (Perisoreus canadensis) carried flight-loads of different weights. Three individually identifiable Gray Jays weighing 60, 68, and 80 grams, used their bills to carry flight-loads weighing up to 33 percent of bodyweight but transferred heavier flight-loads from their bills to their feet 1-2 meters after takeoff. They had difficulty carrying flight-loads over 57 percent of bodyweight, and none attempted to carry flight-loads over 66 percent of bodyweight. By using their feet to bring heavy flight-loads closer to the center of lift, Gray Jays can carry heavier loads of meat, relative to body weight, than can Common Ravens (Corvus corax) which compete with Gray Jays at carcasses in winter and which do not carry objects with their feet. During 1969-2003, year-round observations near the southern edge of the Gray Jay range in northeastern Minnesota showed that caching behavior begins in August, continues over-winter, and ends at the onset of insect activity and green-up in early May. Gray Jays’ propensity to approach larger animals, including people, may not indicate unwariness but rather a superior ability and willingness to assess risks and food benefits. In the boreal forest in winter, risk of starvation is greater and risk of predation is lower than in relatively food-rich ecoregions farther south.

Variation in the Mating System of a Biparental Cichlid Fish, Cichlasoma Panamense

Behaviour ◽  
1985 ◽  
Vol 95 (3-4) ◽  
pp. 181-197 ◽  
Author(s):  
R.J. Wootton ◽  
T.J. Townshend
Keyword(s):  
Game Theory ◽  
Sex Ratio ◽  
Parental Care ◽  
Attack Rate ◽  
Brood Size ◽  
Cichlid Fish ◽  
Dry Season ◽  
Water Levels ◽  
Time Away ◽  
A Current

AbstractCichlasoma panamense is a biparental, substrate-spawning cichlid which breeds during the dry season in Panamanian streams. In one population some males helped to defend their offspring throughout the period of parental care but many deserted their mates to achieve additional spawnings leaving females to guard alone. The proportion of C. panamense guarding in pairs increased throughout the breeding season. This was associated with an increase in the rate with which parental cichlids attacked potential brood predators and an increase in brood size. The increase in attack rate was due to the crowding of fishes as water levels receded during the dry season and especially to the increasing numbers of newly independent cichlids which congregated in the shallow water areas where C. panamense brood. The sex ratio in the population was strongly biased towards females. Males spent more time away from the brood than females which enabled them to find and spawn with unmated females. The attack rate of females brooding alone was not significantly higher than that of those with mates and their foraging rate not significantly lower although they spent less time away from their brood. In a more productive stream where population density was high, breeding was almost entirely in monogamous pairs. The rate at which parents attacked potential predators was higher, the sex ratio was 1:1 and brood size was large. The male's decision to guard or desert appears to depend on his opportunities for further matings, the ability of the female to guard alone and the value of a current brood. These results agree with the predictions of game theory models of parental care.

scholarly journals Absence of complementary sex determination in Trichogramma dendrolimi Matsumura (Hymenoptera: Trichogrammatidae)

2019 ◽  
Author(s):  
Quan-quan Liu ◽  
Jin-cheng Zhou ◽  
Chen Zhang ◽  
Qian-jin Dong ◽  
Su-fang Ning ◽  
...  
Keyword(s):  
Sex Ratio ◽  
Sex Determination ◽  
Brood Size ◽  
Indirect Evidence ◽  
Parasitoid Wasp ◽  
Mass Rearing ◽  
Diploid Male ◽  
Diploid Males ◽  
Offspring Sex Ratio ◽  
Complementary Sex Determination

Over 60 species in Hymenoptera have been reported to possess a complementary sex determination (CSD) system. Under CSD, sex is determined by allelic complementation at one or several sex loci. But this mechanism is still uninvestigated in parasitoid wasp Trichogramma dendrolimi, one of the most important biocontrol agents widely used against Lepidopteran pests. We tested CSD in this species by conducting ten consecutive generations of inbreeding, to monitor both direct evidence (diploid male production) and indirect evidence (brood size, sex ratio, mortality). In total 475 males detected from this inbreeding regime, only one was determined as diploidy. The observed proportions of diploid male offspring significantly differed from expected values under CSD model involving up to ten independent loci, allowing us to safely reject CSD in T. dendrolimi. Meanwhile, the possibility of unviable diploid males was excluded by the absence of significant differences in brood size, offspring sex ratio and offspring mortality among different generations. Our study of sex determination in T. dendrolimi provides useful information for the mass rearing conditions in a biofactory and the quality improvement of this biocontrol agent. It also brings necessary background to further study of the sex determination in Trichogramma.

scholarly journals No Evidence for Adaptive Differential Sex Allocation in Red Junglefowl (Gallus Gallus)

The Auk ◽  
2005 ◽  
Vol 122 (4) ◽  
pp. 1161-1168
Author(s):  
Timothy H. Parker
Keyword(s):  
Sex Ratio ◽  
Brood Size ◽  
Sex Allocation ◽  
Gallus Gallus ◽  
Ratio Analysis ◽  
Maternal Condition ◽  
Sperm Donor ◽  
Sex Ratio Bias ◽  
Red Junglefowl ◽  
Ratio Data

Abstract In many situations, selection should favor females that bias the sex ratio of their offspring. Two commonly examined factors potentially influencing off- spring sex ratio are paternal ornamentation and maternal condition. Male junglefowl with larger combs are attractive to females. I housed female Red Junglefowl (Gallus gallus) with sterile male consorts and artificially inseminated them with sperm from other males that the females never saw. I found no relationship between either the comb size of the consort or the comb size of the sperm donor and the sex ratio of the offspring. I previously reported a significant sex ratio bias related to maternal mass in Red Junglefowl. However, that analysis was based on sex ratio data not weighted for brood size and assuming a normal distribution. Here, I show that this effect disappears when I conduct a more appropriate analysis weighting sex ratio according to brood size and accounting for the binomial error distribution. I also failed to find evidence that male chicks hatch from larger eggs than female chicks. These results suggest that Red Junglefowl females may not bias the sex ratio of their brood in response to either their own condition or the attractiveness of the males with whom they copulate. Furthermore, these results demonstrate the importance of choosing the correct methods of sex ratio analysis. Falta de Evidencia de Asignación Adaptativa Diferencial entre Sexos en Gallus gallus

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