Return Rate Of Males Research Articles

Agonistic song rate positively correlates with male breeding success and avian malaria infection in Acrocephalus paludicola (Aquatic Warbler), a promiscuous songbird with female-only parental care

Abstract The link between male song and reproductive success has been explored at length in socially monogamous birds, but results were inconsistent and under-represented socially non-monogamous species with uniparental care. Here, we evaluated whether metrics of male song in Acrocephalus paludicola (Aquatic Warbler), a promiscuous songbird with female-only care and large repertoires, are associated with fitness- and quality-related traits. We showed that the number of 9-day-old nestlings fathered and probability of avian malaria infection increased with the rate of agonistic song, produced in male–male interactions, and that male-scaled mass index (proxy for energy reserves) positively correlated with the repertoire size. The male breeding success was not explained by repertoire size and song duty cycle. None of the song variables clearly explained the male return rate or change in the tarsus length (proxy for structural body size) and scaled mass index of the fathered chicks between days 2 and 9 post-hatch. No other relationships between the song characteristics and the inbreeding coefficient, scaled mass index, wing-length and Trypanosoma infection status of the males were supported, and Plasmodium infection was unrelated to the song duty cycle and repertoire size. We conclude that in male A. paludicola the repertoire size could be a signal of early developmental stress or current body condition, and the agonistic song rate could be shaped by sexual selection and signal to females a genetic makeup that enhances survival upon infection by Plasmodium.

Sea buckthorn berries Hippophae rhamnoides L. predict size and composition of a great tit population Parus major L

In seasonal environments variation in food abundance in the non‐breeding season is thought to affect songbird population dynamics. In a unique tit‐sea buckthorn berry system we can estimate the berry abundance and both the tit consumption and population dynamics. Six hundred nest boxes were available to great and blue tits Cyanistes caeruleus for breeding in spring and roosting in winter. We followed the dynamics including the recapture histories of individually marked great tits from 2008 to 2014. In each year we estimated 1) the winter sea buckthorn berry availability, 2) an index of berry consumption in December based on the colour of the faeces of roosting birds, 3) the number of breeding great and blue tits, 4) both recapture probability and the return rate of the great tits and 5) immigration rates. December berry abundance positively predicted the number of breeding pairs of both species in the subsequent season and great tit return rates in the second half of the winter. There was support for a sex specific berry effect on the adult return rate in the great tit: female return rate was associated less strongly to berry abundance than male return rate. This skewed the sex ratio of the local breeders in the following breeding season. Intriguingly, annual berry consumption in December was not related to berry abundance, and individuals consuming more berries tended to have slightly lower return rates. Reproductive rate was not related to berry abundance. There was hardly support for a relation between immigration rates of first year breeders and berry abundance. Taken together these results imply that berry stock not only affected population size but also the population composition through sex specific exchange with the surroundings. Since population density covaried with berry abundance, density dependent effects provide an alternative explanation for the patterns observed.

Estimation of the Wage and Employment Equation Model on Urban Labor Market by the Simultaneous Maximum Likelihood Method

This paper estimates wage and employment equation model on urban labor market by the simultaneous maximum likelihood method with CHIP-2002. The results show: human capital, personal ability and father’s education background of a person will affect his/her market wage; Partner’s income and preschool children have a negative effect on female employment probability but have no effect on male employment probability; Female return rate to education is 9.65% and employment elasticity to wage is 1.27; Male return rate to education is 5.93% and employment elasticity to wage is 0.45; Conventional Heckman two step procedure and Probit MLE underestimate the return rate to education and employment elasticity to wage.

Telomere length, non‐breeding habitat and return rate in male American redstarts

Summary Telomeres are long repetitive noncoding sequences of DNA located at the ends of chromosomes. Recently, the study of telomere dynamics has been increasingly used to investigate ecological questions. However, little is currently known about the relationships that link environmental conditions, telomere dynamics and fitness in wild vertebrates. Using a small migratory bird (American redstart, Setophaga ruticilla), we investigated how telomere dynamics can be affected by non‐breeding habitat quality and to what extent telomere length can predict the return rate of males. We show that telomeres shorten in most individuals over a 1‐year period and, importantly, that telomeres of individuals wintering in a low‐quality habitat shorten more than those of individuals wintering in a high‐quality habitat. In addition, we found that longer telomeres are associated with a higher return rate than shorter telomeres, although the relationship between return rate and telomere length did not depend on habitat quality. Our study suggests that telomere dynamics are affected by environmental conditions and are related to indices of fitness in a migratory bird species.

Manipulation of Life-History Decisions Using Leptin in a Wild Passerine

Seasonal timing of reproduction and the number of clutches produced per season are two key avian life-history traits with major fitness consequences. Female condition may play an important role in these decisions. In mammals, body condition and leptin levels are correlated. In birds, the role of leptin remains unclear. We did two experiments where we implanted female great tits with a pellet releasing leptin evenly for 14 days, to manipulate their perceived body condition, or a placebo pellet. In the first experiment where females were implanted when feeding their first brood offspring we found, surprisingly, that placebo treated females were more likely to initiate a second brood compared to leptin treated females. Only one second brood fledged two chicks while five were deserted late in the incubation stage or when the first egg hatched. No difference was found in female or male return rate or in recruitment rate of fledglings of the first brood, possibly due to the desertion of the second broods. In our study population, where there is selection for early egg laying, earlier timing of reproduction might be hampered by food availability and thus nutritional state of the female before egg laying. We therefore implanted similar leptin pellets three weeks before the expected start of egg laying in an attempt to manipulate the laying dates of first clutches. However, leptin treated females did not initiate egg laying earlier compared to placebo treated females, suggesting that other variables than the perceived body condition play a major role in the timing of reproduction. Also, leptin treatment did not affect body mass, basal metabolic rate or feeding rates in captive females. Manipulating life history decisions using experimental protocols which do not alter individuals' energy balance are crucial in understanding the trade-off between costs and benefits of life history decisions.

Factors Responsible for the Long-Term Dynamics of the Pied FlycatcherFicedula hypoleucaPopulations in the Taiga of Karelia, Russia

Abstract. A Pied Flycatcher population breeding in nest-boxes in a Karelia forest was studied from 1981 to 2007. Breeding density varied between 47.3 and 94.6 pairs/km2. The density of the breeding population was influenced by three demographic factors: maximum summer population density in the previous season, male return rate and immigration rate. Three relatively independent processes play a significant part in the population dynamics of the study area: 1) initial abundance and reproductive intensity, 2) survival rate between breeding seasons, and 3) redistribution of birds across their range. The weather in spring, when the birds arrive and settle, was found to be equally important. The population density, nest site fidelity of adults and yearlings, and immigration rate were related to temperature patterns in May. It may be assumed that the spring weather influences the birds' survival and their distribution across the northern part of their range, as well as the participation of one-year old birds in ...

A PIT tag based analysis of annual movement patterns of adult fire salamanders (Salamandra salamandra) in a Middle European habitat

AbstractWe studied patterns of annual movement of individual adult fire salamanders (Salamandra salamandra) during the years 2001 and 2002 in Western Germany in a typical middle European habitat for this species. We tested whether salamanders inhabit small home ranges and move little during the activity period as predicted for a species that shows strong site fidelity to a limited area. Initially, 98 individuals were collected in their natural habitat and marked with passive integrated transponder (PIT) tags. Of those individuals 88 were released at the collection site for recapture during the activity periods of the years 2001 and 2002. Ten marked individuals were kept in captivity to test for the tolerance of PIT tags. We did not find any negative impact of PIT tags on marked individuals of S. salamandra, neither under captive nor natural conditions. Forty-seven of the marked individuals (corresponding to 53% of the 88 released ones) were recaptured at least once and 28 individuals (corresponding to 32%) were recaptured multiple times. The return rate of males (78%) was higher than for females (43%). Mean home range size (and standard deviation) was estimated to 494 ± 282 m2 for 4 individuals as the minimum convex polygon based on 5 to 6 recapture events for each individual per year and to 1295 ± 853 m2 for 3 individuals with 8 records over two years. Minimum distances moved inferred from individual recaptures increased during the activity period of both years with time, indicating that individuals have more of a tendency to disperse than to stay within a limited area. Our data suggest therefore that S. salamandra adults display site fidelity, but use a much larger area than hitherto documented for this and other terrestrial salamander species.

Long-term decline in a red-winged blackbird population: ecological causes and sexual selection consequences

Habitat loss and large-scale climate phenomena are widely implicated as causing decline in animal populations. I examined how both factors contributed to a precipitous decline in an Ontario red-winged blackbird (Agelaius phoeniceus) population using 16 years of data collected between 1974 and 1995. The decline was manifested as an almost 50% reduction in mean harem size, which reduced the opportunity for sexual selection threefold. Regional hay production, which should affect recruitment into the study population, also declined substantially. Correlation between blackbirds and hay may be coincidental, however, because annual changes in harem size were not associated with annual changes in hay production. This study coincided with an unprecedented positive phase of the North Atlantic Oscillation (NAO). Changes in harem size were correlated with winter NAO index values, suggesting that winter mortality contributed to the population decline. Positive correlation between harem size change and male return rates also supported the winter mortality hypothesis. Continued declines will cause this blackbird population to change from socially polygynous to socially monogamous. Study of red-winged blackbird winter ecology is needed to identify the proximate causes of mortality, whereas breeding studies can explore the consequences of relaxed sexual selection.

REPRODUCTIVE EFFORT AND RETURN RATES IN THE MOUNTAIN WHITE-CROWNED SPARROW

Abstract We analyzed return rates of high-altitude-breeding Mountain White-crowned Sparrows (Zonotrichia leucophrys oriantha) in relation to five components of their previous season's reproductive effort: number of fledglings produced, double brooding, number of nesting attempts (first nests plus renests), total number of eggs laid, and fledging date. No relationship of return rate to reproductive effort occurred except in the case of fledging date. Fledging dates spanned a 2-month period from mid-June to mid-August. Returns of females to the study area held steady no matter when their chicks fledged in the previous breeding season, but male return rates increased significantly when their chicks fledged after 20 July. Coincident with that time frame, they entered molt and often withdrew parental care. We hypothesized that males in this montane environment, where thermoregulatory costs are high, traded off reproductive effort (parental care) with survival (return rates). This fits well with models of life-...

Homing of Translocated Brown Bears (Ursus arctos) in Coastal South-Central Alaska

Sixteen brown bears (Ursus arctos) were translocated an average of 148 km from the Copper River Delta, Alaska, in 1987. Of 13 bears that were radio collared, 6 returned to their original home range, 3 remained in the release area, and the final locations of 4 were unknown. Overall homing success was similar to that observed in interior Alaska; however, contrary to the findings of others, the return rate of males >3 yr old (2 of 5) was less than that of females >3 yr old (4 of 4). This may have been the result of a vacuum created by a higher harvest of bears in the release area, relative to the Copper River Delta, during the 5 yr prior to the study. The results of this study provide additional evidence that translocation of nuisance bears has a high probability of failure due to their strong homing instinct.

Numbers and Production of Eurasian Wigeon in Relation to Conditions in a Breeding area, Lake Myvatn, Iceland

1. A migratory breeding population of Eurasian wigeon Anas penelope L., was studied over the period 1975-95 on 54 km 2 of freshwater habitat at Lake Myvatn, northern Iceland. Spring numbers of males averaged 1076 (range 526-1887). The sex ratio was 0.97 females per male and the proportion of yearling males averaged 0.21. The mean brood was 3.93 and a mean of 2.83 young per female (range 0.09-5.14) was produced. Production of young was positively related to chironomid abundance and negatively to cold and wet weather. 2. Both sexes seem to be faithful to their winter range, but males are much less faithful to the summer range than are females. The apparent return rate of males is presumably an expression of the return rate of females, which had previously bred locally or been produced at Myvatn. 3. The apparent return rate of old males (2 years or older), mean 0.84 (range 0.58-l.22), was positively correlated with chironomid abundance in the previous summer, which varied greatly. It is suggested that abundant chironomids in late summer may provide a source of highly nutritious food which would increase the probability of wigeon returning to Myvatn or favour the survival of Myvatn wigeon on winter grounds shared with birds originating from other breeding areas. Chironomid numbers showed serial correlation, hence it may be advantageous for the birds to assess the food supply before departure and return accordingly. 4. The apparent return rate of yearling males, mean 0.22 (range 0.06-0.56), was negatively related to the number of young produced in the year before. 5. The density of breeding wigeon at Lake Myvatn was mainly determined by food conditions in the breeding area, as experienced by the adults 1 year previously, and events in the winter range appeared to have less influence. Flyway populations may be limited by a complex set of local and global fluctuations in resources in (i) breeding localities, determining density and production in each, coupled with (ii) staging and wintering localities in each of which local resources would determine density.

Low male return rate due to clutch enlargements in the pied flycatcher (Ficedula hypoleuca)

:Increased investment in reproduction during current breeding event may entail future fitness costs. Even though a wide array of both theoretical and empirical work has been devoted to solve the problem of optimal reproductive rate, evidence for costs of reproduction has been equivocal. In the present study we examined the survival of pied flycatcher parents after a clutch size manipulation where we altered clutch size with one or two eggs. We monitored return rates and dispersal of parents during subsequent years after manipulation. An artificial increase in reproductive effort caused lowered return rates of males. Results on breeding dispersal did not support the explanation that observed low return rate was due to differences in dispersal. Thus, it seemed that low return rate of males with increased reproductive effort was due to lower local survival. No survival cost on females was evident, but return rate of females was too low for a proper test. An analysis on reproductive success revealed that within treatment groups the returning males tended to be more successful in their previous reproductive event than non-returning ones. These results together imply that phenotypic quality of individuals varies considerably causing fitness differences between individuals.

SITE FIDELITY IN HIGH ARCTIC BREEDING WADERS

Summary Tomkovich, P.S. & Soloviev, M.Yu. 1994. Site fidelity in High Arctic breeding waders. Ostrich 65:174-180. The return rate and fluctuations in density between years were determined for colour-marked populations of Grey Plover Pluvialis squatarola. Little Stint Calidris minuta, Curlew Sandpiper C. ferruginea, Sanderling C. alba and Knot C. canutus in a study in the Knipovich Bay area, northern Taimyr, Central Siberia (76°05'N. 98°32'E) during three breeding seasons, June 1990 to August 1992. No birds marked as chick were recorded as returning to the study area. Females of all species exhibited low site fidelity. The return rate of males varied between species. No marked male Curlew Sandpiper or Little Stint were recorded in the season following the marking, which is compatible with the nomadic behaviour of these two species. In contrast, males of Grey Plover and Knot were site faithful and had return rates of 78% and 8% respectively (though the latter value may have been underestimated). Site fideli...

Breeding ecology of the Aquatic Warbler Acrocephalus paludicola on the Biebrza marshes, northeast Poland

Aquatic Warblers Acrocephalus paludicola were studied in a natural fen mire in the Biebrza River valley, the main breeding ground of the species in its entire distribution range. The number of males present and singing at the sample plot changed considerably during the breeding season. Individual identified colour‐ringed males sang with unchanged intensity throughout the breeding season. The period of daily singing activity differed from other species of Acrocephalus; males sang at dusk rather than at dawn. Males took no part in rearing nestlings but remained on territory and showed vigilance behaviour. The density of males in the breeding season ranged from 1.0 to 10.9 per 10 ha. The density of nesting females ranged from 1.3 to 15.7 per 10 ha. In the most suitable habitat females were more numerous than males. The distribution of females (nests) was clumped where potential food resources were higher. Nests were well hidden in places with deeper water between sedge tufts and an abundance of old dry sedge. Females feeding nestlings collected most food within a 5–60‐m radius (mean 31.7 m). The return rate of males was higher than that of females. The results suggest a mating system that is intermediate between facultative polygyny and promiscuity.