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Breeding Date (breeding + date)
Selected AbstractsBrood reduction in the Red-necked Grebe Podiceps grisegenaIBIS, Issue 2 2003Janusz Kloskowski Brood reduction in Red-necked Grebes Podiceps grisegena breeding on fish ponds in south-eastern Poland occurred either through the desertion of the last-laid eggs after partial hatching of the clutch and/or the selective starvation of the smallest chicks. Abandonment of unhatched eggs was not influenced by the number of young already hatched or by the breeding date, but it was more likely in larger clutches and in families suffering chick starvation. Chicks from the largest broods had a higher probability of survival until fledging than those from single-chick broods. Larger chicks obtained food more successfully through better positioning during food delivery. In families that did not suffer brood reduction, chicks were better provisioned with food than in reduced broods. Although allocation of food among chicks in reduced broods was more skewed to the disadvantage of the younger siblings, dominant chicks obtained less food prior to brood reduction than dominant siblings in unreduced broods. Sibling aggression did not differ between unreduced and reduced broods before death of the weakest chicks. Post-laying adjustment of the number of offspring to prevailing feeding conditions occurred at two stages: by parental manipulation of the number of hatched eggs at the time when parents and chicks leave the nest and by competition between chicks. It is suggested that late egg desertion may be an adaptive mechanism of brood-size adjustment, when elimination of the weakest chicks through sibling competition is not very efficient. [source] Carry-over effects in a Pacific seabird: stable isotope evidence that pre-breeding diet quality influences reproductive successJOURNAL OF ANIMAL ECOLOGY, Issue 2 2009Marjorie C. Sorensen Summary 1Understanding the interactions between different periods of the annual cycle in migratory animals has been constrained by our inability to track individuals across seasons. In seabirds, virtually nothing is known about how diet quality during the non-breeding period, away from the breeding grounds, might influence subsequent reproductive success. 2We used stable nitrogen (,15N) and carbon (,13C) isotopes to evaluate the effects of non-breeding diet quality on the timing of breeding and egg size in a population of Cassin's auklets (Ptychoramphus aleuticus) breeding on Triangle Island, British Columbia. Adult feathers are grown during two different periods of the annual cycle, which allowed us to estimate diet quality from the previous fall (October,November) and pre-breeding (February,March) period. 3We found that the estimated proportion of energetically superior copepods (Neocalanus spp.) in the pre-breeding diet tended to be higher in females that bred earlier and laid larger eggs, whereas energetically poor juvenile rockfish (Sebastes spp.) were dominant in the pre-breeding diets of females that bred later and laid smaller eggs. We detected no effect of fall diet quality on breeding date or egg size, and no effect of pre-breeding diet quality on breeding date in males. 4Pre-breeding diet quality was not related to body condition measured 1,2 days after laying, which suggests that females may need to attain a threshold condition before they initiate breeding and successfully rear young. 5Our results suggest that changes in climatic conditions during the pre-breeding period may have severe consequences for reproductive success by influencing breeding date and egg size. Our work emphasizes the importance of determining how events are linked throughout the annual cycle for understanding the fitness and population dynamics of migratory animals. [source] Climatic effects on timing of spring migration and breeding in a long-distance migrant, the pied flycatcher Ficedula hypoleucaJOURNAL OF AVIAN BIOLOGY, Issue 5 2005Christiaan Both Climate change has advanced the breeding dates of many bird species, but for few species we know whether this advancement is sufficient to track the advancement of the underlying levels of the food chain. For the long-distance migratory pied flycatcher Ficedula hypoleuca the advancement in breeding time has been insufficient to maintain the synchrony with their main food sources. The timing of arrival in the breeding areas from their African wintering grounds is likely to constrain the advancement of breeding date. We hypothesise that this is because in Africa they cannot predict the advancement of spring in their breeding habitat. However, long-distance migrants may advance their arrival time by migrating faster when circumstances en route are favourable. In this study we show that both arrival and breeding date depend on temperatures at their main North African staging grounds, as well as on temperature at the breeding grounds. Male arrival and average laying date were not correlated, but the positive effect of temperature in North Africa on breeding dates suggests that breeding date is indeed constrained by arrival of females. Long-distance migrants thus are able to adjust arrival and hence breeding by faster spring migration, but the degree of adjustment is probably limited as timing schedules in spring are tight. Furthermore, as climate change is affecting temperatures differently along the migratory flyway and the breeding areas, it is unlikely that arrival dates are advanced at the same rate as the timing of breeding should advance, given the advancement of the underlying levels of the food chain. [source] Intrapopulation variation in reproduction by female eastern kingbirds Tyrannus tyrannus: the impacts of age, individual performance, and breeding siteJOURNAL OF AVIAN BIOLOGY, Issue 3 2004Michael T. Murphy I used data from a 13-year study of eastern kingbirds Tyrannus tyrannus from central New York, USA, to evaluate the relative impact of female age and body size on reproduction. I also calculated repeatabilities of reproductive traits for both females and the sites where they bred in an attempt to evaluate the relative contribution of each to intrapopulation variation in reproduction. Female age had a strong influence on timing of breeding (breeding date advanced by one day for each year of life), but was not a significant source of variation for clutch size, egg mass, number of young to hatch or fledge, or total seasonal production. Repeatabilities of breeding date for females and sites were both significant (0.284 and 0.181, respectively), but the only other significant repeatabilities were for female clutch size (0.282) and female egg mass (0.746). Among-year repeatabilities of breeding date for females who bred at two or more sites over their lifetime were as high as those for females that were site faithful. Thus, breeding date was probably affected independently by the female and site. No measure of productivity exhibited a repeatable pattern in comparisons made among females or sites. All reproductive traits were entered as dependent variables in a series of stepwise multiple regression analyses in an attempt to identify female properties (size, lifespan and condition) that might be linked proximately to differences in breeding statistics. I found that (a) large birds tended to breed the earliest, (b) clutch size was independent of female size, condition and lifespan, (c) female body size and egg size were correlated positively, but (d) production of young was independent of all measured female properties. Reproduction appears to be linked more closely to the female than to the site. Body size accounts for a portion of the repeatable portion of breeding date and egg mass, but most of the intrapopulation variation in these and other traits remained unexplained. [source] Variable reproductive effort for two ptarmigan species in response to spring weather in a northern alpine ecosystemJOURNAL OF AVIAN BIOLOGY, Issue 3 2010Scott Wilson Predicting how animal populations respond to climate change requires knowledge of how species traits influence the response of individuals to variation in anuual weather. Over a four-year study with two warm and two cold years, we examined how sympatric rock ptarmigan Lagopus muta and white-tailed ptarmigan L. leucura in the southern Yukon Territory respond to spring weather in terms of breeding phenology and the allocation of reproductive effort. The onset of breeding was approximately synchronous; for each one-degree rise in spring temperature, mean breeding dates of rock and white-tailed ptarmigan advanced by about 2.7 and 4 days respectively. Although onset of breeding was similar, the two species differed in their reproductive effort. As breeding was delayed, average first clutch sizes of rock ptarmigan declined from 9.4 to 5.8 eggs over the breeding period, while those of white-tailed ptarmigan only declined from an average of 7.8 to 6.8. Rock ptarmigan were also less likely to re-nest if their first clutch was lost to predators and as a consequence they had shorter breeding seasons. White-tailed ptarmigan produced about 25% more offspring annually than rock ptarmigan and contributed more young through re-nesting. While white-tailed ptarmigan had higher annual reproductive output, adult rock ptarmigan had a 20,25% higher annual survival rate, which may indicate a reproduction,survival trade-off for the two species. These results show that even within the same location, closely related species can differ in how they allocate effort as environmental conditions fluctuate. [source] Climatic effects on timing of spring migration and breeding in a long-distance migrant, the pied flycatcher Ficedula hypoleucaJOURNAL OF AVIAN BIOLOGY, Issue 5 2005Christiaan Both Climate change has advanced the breeding dates of many bird species, but for few species we know whether this advancement is sufficient to track the advancement of the underlying levels of the food chain. For the long-distance migratory pied flycatcher Ficedula hypoleuca the advancement in breeding time has been insufficient to maintain the synchrony with their main food sources. The timing of arrival in the breeding areas from their African wintering grounds is likely to constrain the advancement of breeding date. We hypothesise that this is because in Africa they cannot predict the advancement of spring in their breeding habitat. However, long-distance migrants may advance their arrival time by migrating faster when circumstances en route are favourable. In this study we show that both arrival and breeding date depend on temperatures at their main North African staging grounds, as well as on temperature at the breeding grounds. Male arrival and average laying date were not correlated, but the positive effect of temperature in North Africa on breeding dates suggests that breeding date is indeed constrained by arrival of females. Long-distance migrants thus are able to adjust arrival and hence breeding by faster spring migration, but the degree of adjustment is probably limited as timing schedules in spring are tight. Furthermore, as climate change is affecting temperatures differently along the migratory flyway and the breeding areas, it is unlikely that arrival dates are advanced at the same rate as the timing of breeding should advance, given the advancement of the underlying levels of the food chain. [source] | ||||||||||