Study On Breeding Tactics And Fitness Of Double-Breeding In Great Tits(Parus Major)in Temperate Regions

The fecundity of birds could be maximized by increasing the clutch size in a given nesting attempt or by increasing the number of breeding attempts during breeding season.Producing two broods within the same season is a common reproductive strategy among temperate passerines.However,it is necessary to mark,track and recapture individual to conduct the research on birds double-breeding,which leads to less related research in domestic and abroad,therefore,the research double-breeding of lag behind the current overall level of ornithological research.Our team previous found that a part of individuals in the Great Tit(Parus major)population produced a second clutch after successfully raising a first clutch within breeding seasons.However,the time allocation tactics of different breeding stages and the tactics of mate selection on double breeding Great Tit have not been clarified yet.From March to July in 2014 to 2016,the researchers conducted relevant research in Zuojia Nature Reserve,employing artificial nest box to attract Great Tit,parents birds were marked with standard aluminium rings.In this study,the reproductive parameters,phenotypic characteristics,characteristics of the nest site,dawn song of the male,genetic quality of mate and fecundity of Great Tit have been analyzed.The hypotheses of time allocation,reproductive investment and mate choice for double-breeding of Great Tit have been tested systematically.The breeding tactics and fitness of double-breeding Great Tits in temperate regions have been explored.In this study,we monitored 606 artificial nesting boxes and recorded the breeding parameters of the Great Tits such as nesting-build date,first egg laying date,hatching data and fledgling date.We tracked that 22(30.1%)of the 73 successful nests of Great Tit produced a second clutch after successfully raising a first clutch within breeding seasons.This study found that: the probability of double breeding decreased with prolonged nest building period and nestling period,the laying date delay.Double breeding Great Tit did not reduce the length of egg period and nestling period,but shortened the length of nesting building period to shortened the breeding cycle.They were initiation second clutch with an extraordinary short inter-brood interval by reproduce with original mate and nesting in the vicinity of their first nest.All period of second broods were shorter than first broods.The results showed that there were trade-offs and adjustments in the time allocation between the first and second brood,double breeding Great tits might adopt multiple breeding tactics to ensure the time required to reproduce twice in the same year.By analyzing the tarsus length,breast black stripe width,repertoire size and genetic similarity between spouses of the males in breeding and also the individual heterozygosity and individual F of the males and their offspring,found that double-breeding females prefer males with large breast stripes,high heterozygosity,and lower relatedness,offspring of double-breeding with higher heterozygosity and lower individual F.The results showed that the mate choice of female Great Tits in double-breeding considered both good genes and compatibility genes,which may improve the quality of the offspring.By compared and analyzed the nest-entrance angle,nest entrance orientation,nest height,coverage of nest,tree number within ten meters and average shrub height between the single and double-breeding nest,found that,there was no significant difference in nest characteristics except that nest-entrance angle of the first nest of the double-breeding was more downward than that of the single-breeding.In the second nest of the double-breeding Great Tits,the nest was rebuilt near the first original nest,and the nest-entrance angle was relatively upward than that of the first original nest.The results indicate that nest-entrance angle and distance from the original nest may affect the nest selection of double-breeding Great tit,the pattern may be conducive to reduce the time and energy consuming for re-evaluating the territory quality and the nest selection.By compared the number of offspring and paternity,individual F and individual heterozygosity of the offspring and parents,genetic similarity between spouses,tarsus length,breast black stripe width and repertoire size of males among single-breeding and double-breeding Great Tits,found that no extramarital offspring was found belong to double-breeding males and female,the number of hereditary offspring of the double-breeding Great Tit was significantly more than that of the single-breeding male engaged in extra-pair copulations and not,the heterozygosity of offspring of double-breeding was significantly higher and individual F was significantly lower than single-breeding female engaged in extra-pair copulations and not.Double-breeding pairs with lower relatedness,double-breeding males with higher heterozygosity than single-breeding male engaged in extra-pair copulations and larger breast stripes than single-breeding male not engaged in extra-pair.The results indicate that double breeding could significantly increase the fitness of the Great Tits,pair with higher quality may choose higher fitness breeding tactics,and double-breeding Great tits without extramarital mate which may be due to the time and energy were consumed in the current breeding offspring.In this study,the results have revealed that: Great Tit could adjust the breeding tactics of the breeding time allocation,select high-quality mates,and reduce the investment in nest site selection to ensure the time required to reproduce twice in the same breeding season.In addition,double-breeding Great Tit not only has the largest number of genetic progeny,but also has high genetic quality of offspring.Therefore,double breeding is efficient breeding tactics in the research population.