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Fledging Success (fledging + success)
Selected AbstractsSpatial differences in breeding success in the pied avocet Recurvirostra avosetta: effects of habitat on hatching success and chick survivalJOURNAL OF AVIAN BIOLOGY, Issue 4 2006Szabolcs Lengyel I studied the breeding biology of pied avocets Recurvirostra avosetta in natural habitats (alkaline lakes), and in semi-natural sites (dry fishpond, reconstructed wetlands) in Hungary to relate habitat selection patterns to spatial and temporal variation in breeding success. Colonies were initiated earlier in semi-natural sites than in natural habitats, and earlier on islands than on the mainland. Hatching success was higher on islands than on the mainland, in semi-natural sites than in natural habitats, in colonies of at least 15 pairs than in smaller colonies, and for nests initiated earlier than later within a colony. Fledging success was higher in the wet years (1999,2000) than in the dry year (1998), decreased strongly by season in both habitats and increased with average daily temperature in the first week post-hatch in 1999,2000. Most pairs hatching young in semi-natural sites attempted to lead their chicks to feeding areas in natural habitats, whereas no such movement occurred in the opposite direction. Chick mortality due to predation was high during brood movements and only 23% of the pairs moving their young produced fledglings, compared to 43% for pairs remaining in semi-natural sites and 68% for pairs hatching and rearing young in natural habitats (total n=192 broods). These results suggest that semi-natural sites were more suitable for nesting, whereas natural habitats were more suitable for chick-rearing. The opposing trends in habitat-related breeding success between nesting and chick-rearing suggest sub-optimal habitat selection by Pied Avocets due to an incorrect assessment of the potential for successful reproduction of semi-natural sites, which may thus function as ecological traps. [source] Hatching asynchrony and growth trade-offs within domesticated and wild zebra finch, Taeniopygia guttata, broodsBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2010MARK C. MAINWARING The Australian zebra finch, Taeniopygia guttata, is a widely used model organism, yet few studies have compared domesticated and wild birds with the aim of examining its relevance as an evolutionary model species. Domestic and wild broods hatch over approximately 4 and 2 days, respectively, which is important given that nestlings can fledge after as little as 12 days, although 16,18 days is common. We aimed to evaluate the extent to which the greater hatching asynchrony in domestic stock may effect reproductive success through greater variance in size hierarchies, variance in within-brood growth rates, and partial brood mortality. Therefore, by simultaneously controlling brood sizes and experimentally manipulating hatching intervals in both domesticated and wild birds, we investigated the consequences of hatching intervals for fledging success and nestling growth patterns, as well as trade-offs. Fledging success was similarly high in domestic and wild broods of either hatching pattern. Nonetheless, between-brood analyses revealed that domestic nestlings had significantly higher masses, larger skeletal characters, and longer wings than their wild counterparts, although wild nestlings had comparable wing lengths at the pre-fledging stage. Moreover, within-brood analyses revealed only negligible differences between domestic and wild nestlings, and larger effects of hatching order and hatching pattern. Therefore, despite significant differences in the hatching intervals, and the ultimate size achieved by nestlings, the domestication process does not appear to have significantly altered nestling growth trade-offs. The present study provides reassuring evidence that studies involving domesticated zebra finches, or other domesticated model organisms, may provide reasonable adaptive explanations in behavioural and evolutionary ecology. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 763,773. [source] Effect of abiotic factors on reproduction in the centre and periphery of breeding ranges: a comparative analysis in sympatric harriersECOGRAPHY, Issue 4 2001J. T. García Variables such as weather or other abiotic factors should have a higher influence on demographic rates in border areas than in central areas, given that climatic adaptation might be important in determining range borders. Similarly, for a given area, the relationship between weather and reproduction should be dissimilar for species which are in the centre of their breeding range and those that are near the edge. We tested this hypothesis on two sympatric ground-nesting raptors, the hen harrier Circus cyaneus and the Montagu's harrier Circus pygargus in Madrid, central Spain, where the hen harrier is at the southern edge of its breeding range in the western Palearctic and the Montagu's harrier is central in its distribution. We examined the reproductive success of both species during an 8-yr period, and looked at the influence of the most stressful abiotic factors in the study area (between-year variation in rainfall and within-year variation in temperature) on reproductive parameters. In the hen harrier, low levels of rainfall during the breeding season had a negative influence on annual fledging success and thus on population fledgling production. The relationship between rainfall and reproduction was probably mediated through food abundance, which in Mediterranean habitat depends directly on rainfall levels. In the Montagu's harrier, no negative effect of dry seasons on productivity was found. Additionally, in the hen harrier, the proportion of eggs that did not hatch in each clutch increased with higher temperatures during the incubation period. No such relationship was found in the Montagu's harrier. We interpret these between-species differences in terms of differences of breeding range and adaptations to the average conditions existing there. Hen harriers, commonest at northern latitudes, are probably best adapted to the most typical conditions at those latitudes, and have probably not developed thermoregulatory or behavioural mechanisms to cope with drought and high temperatures in Mediterranean habitats, in contrast to Montagu's harrier. Thus hen harrier distribution might be constrained by these variables, due to lower reproductive success or higher reproductive costs. Accordingly, a logistic regression analysis of the presence or absence of both species in 289 random points throughout the western Palearctic showed that the distribution of both species was related to temperature, but the relationship was in opposite directions for the two species: hen harriers had lower probability of breeding in areas with higher temperature (as expected in a species with a more northerly distribution). [source] Experimentally Constrained Virulence is Costly for Common Cuckoo ChicksETHOLOGY, Issue 1 2009Grim Chicks of some avian brood parasites show high virulence by eliminating all host progeny in the nest whereas others develop in the presence of host nestmates. Common cuckoo (Cuculus canorus) chicks are typically highly virulent parasites as they attempt to evict all host eggs and chicks soon after hatching. However, several features of nest design, including steep walls and/or cavity nests, may effectively prevent cuckoo hatchlings from evicting nestmates. A previous observational study showed low success of cuckoo chicks in evicting progeny of a cavity nester host, the redstart (Phoenicurus phoenicurus) but cuckoo chicks showed low survival both when reared alone or in mixed broods with host nestmates. Whether poor cuckoo performance was caused by eviction costs and/or by the effect of presence of host chicks per se remains unclear. We experimentally cancelled any potential eviction costs by removing host eggs immediately after the cuckoo hatched and creating mixed broods 5 days later when the eviction instinct of the cuckoo already ceased. Cuckoos that were forced to compete with host nestlings experienced lower provisioning rates, poorer growth, and lower fledging success than control lone cuckoos. Cuckoos in mixed broods that survived until fledging fledged later, and at lower masses, than those in the sole cuckoo group. Thus, the cuckoo gens specializing on redstarts is similar to other cuckoo gentes, whose chicks are more successful in evicting host nestmates, and it does not benefit from the presence of host brood. Cohabitation with host nestlings then should be viewed as a maladaptive by-product of host cavity nest design. [source] Islands in a desert: breeding ecology of the African Reed Warbler Acrocephalus baeticatus in NamibiaIBIS, Issue 4 2001CORINE M. EISING The continental African Reed Warbler Acrocephalus baeticatus, like its relative the Seychelles Warbler Acrocephalus sechellensis, breeds in isolated patches. We studied the mating system of the African Reed Warbler to see whether this species, like the Seychelles Warbler, shows co-operative breeding. The African Reed Warbler is not polygynous. The majority breed monogamously (88%, n= 65), however in 12% of the territories three adult unrelated birds (mostly males) were observed participating in the brooding and feeding of nestlings, suggesting a polyandrous breeding system. Multilocus DNA fingerprinting revealed that the helping bird was unrelated to the pair birds. The percentage of nests with helpers was low compared to rates found in the Seychelles Warbler or Henderson Reed Warbler Acrocephalus vaughani taiti. This could be due to the scarcity of potential helpers or to the fact that, although limited, birds still had the opportunity to disperse within a meta-population structure in search of vacant territories. The presence of helpers was associated with increased hatching success due to lower predation rates, but not with increased fledging success. Another possible benefit of helping behaviour in this species could be improved predator detection and mobbing. Nest predation was high and warblers tended to build their nests in the highest, most dense reed patches available in their territory. There was no relation between habitat quality, measured as insect food availability, and the occurrence of helpers. [source] Breeding biology and breeding success of the Lesser Grey Shrike Lanius minor in a stable and dense populationIBIS, Issue 2 2000ANTON KRISTIN The Lesser Grey Shrike Lanius minor is highly endangered throughout Europe, having declined markedly in abundance and range. Long-term changes in climate and agricultural practices have been identified as the main reasons for its decline. To determine which factors influence short-term changes in breeding success, we examined several aspects of its breeding biology. Our investigation revealed that our study area bears a large and stable population of this species. In 1996 and 1997, we recorded 84 and 77 breeding pairs in an area of 20 km2, with an average of 4.20 and 3.85 pairs/km2 respectively. Data on breeding density, clutch size and fledging success from 1989 to 1997 (excluding 1992) indicate a stable breeding population with a constant high breeding success. Reproductive success declined through the season, mainly through seasonal variation in clutch size rather than chick mortality. However, breeding success was generally high (69% and 79% of the nests produced chicks], with low hatching failure and few nest losses. The main cause of breeding failure was nest predation (at least 50% of nest losses), mainly by magpies (at least 66% of depredated nests). Although in this population the Lesser Grey Shrike tends to aggregate in clusters, breeding density had no obvious effect on breeding success and nest predation. [source] Density dependence in a recovering osprey population: demographic and behavioural processesJOURNAL OF ANIMAL ECOLOGY, Issue 5 2008V. Bretagnolle Summary 1Understanding how density-dependent and independent processes influence demographic parameters, and hence regulate population size, is fundamental within population ecology. We investigated density dependence in growth rate and fecundity in a recovering population of a semicolonial raptor, the osprey Pandion haliaetus [Linnaeus, 1758], using 31 years of count and demographic data in Corsica. 2The study population increased from three pairs in 1974 to an average of 22 pairs in the late 1990s, with two distinct phases during the recovery (increase followed by stability) and contrasted trends in breeding parameters in each phase. 3We show density dependence in population growth rate in the second phase, indicating that the stabilized population was regulated. We also show density dependence in productivity (fledging success between years and hatching success within years). 4Using long-term data on behavioural interactions at nest sites, and on diet and fish provisioning rate, we evaluated two possible mechanisms of density dependence in productivity, food depletion and behavioural interference. 5As density increased, both provisioning rate and the size of prey increased, contrary to predictions of a food-depletion mechanism. In the time series, a reduction in fledging success coincided with an increase in the number of non-breeders. Hatching success decreased with increasing local density and frequency of interactions with conspecifics, suggesting that behavioural interference was influencing hatching success. 6Our study shows that, taking into account the role of non-breeders, in particular in species or populations where there are many floaters and where competition for nest sites is intense, can improve our understanding of density-dependent processes and help conservation actions. [source] Prevalence of avian pox virus and effect on the fledging success of Laysan AlbatrossJOURNAL OF FIELD ORNITHOLOGY, Issue 1 2008Lindsay C. Young ABSTRACT Avian pox virus (Poxvirus avium) is a mosquito-borne disease that occurs worldwide in a variety of bird species, but little is known about its prevalence or effect on seabirds. We monitored prevalence of pox virus and its effect on fledging success of Laysan Albatross (Phoebastria immutabilis) on Oahu, Hawaii, from 2003 to 2007. Pox prevalence in albatross chicks averaged 88% in years with high rainfall and 3% in years with low rainfall. Diagnosis of pox virus was clinically confirmed in two birds by Muscovy Duck (Cairina moschata) fibrolast cultures. Severity of infection ranged from small wart-like nodules and lesions on the bill, face, eyes, tarsus, and feet, to large tumorous growths that completely covered both eyes and caused deformation of the bill and skull. Most chicks recovered from infection, and the fledging rate in pox epizootic years (82%) did not differ from that in years with low pox prevalence (80%) or the average fledging rate on Midway Atoll (86%). Three chicks with severe infections were resighted as healthy adults on Kauai and Oahu in 2007, confirming postfledging survival of at least some birds. The high recovery rate, fledging success, and postfledging survival indicate that Laysan Albatross have strong immunity to avian pox virus. SINOPSIS La viruela aviar (Poxvirus avium) es una enfermedad que afecta muchas especies de aves a nivel mundial. La enfermedad es transmitida por mosquitos y se sabe poco de su prevalencia y efecto en aves acuáticas. Monitoreamos la prevalencia de este virus y su efecto en volantones de albatros (Phoebastria immutabilis) en Oahu, Hawaii, en trabajo que se llevo a cabo desde el 2003,2007. Encontramos una prevalencia de 88% en pichones de albatros en años lluviosos y de 3% en años de poca lluvia. Se diagnosticó el virus, clínicamente, en dos patos comunes (Cairina moschata) mediante la técnica de cultivo fibroblástico. La severidad de la infección varió desde leve con algunas lesiones en el pico, cara, ojos, tarso y patas, hasta casos severos con grandes tumores que cubrían los ojos y causaron malformación de pico y craneo. La mayoría de los pichones se recobraron de la infección. La tasa de pichones que dejaron el nido (82%) en años de alta incidencia (82%) fue similar (80%) a los años de pocas infecciones y al promedio de volantones (86%) en el Atolón de Midway. Tres individuos observados como pichones con infecciones severas fueron avistados posteriormente como adultos saludables en Kauai y Oahu en el 2007, lo que confirma la sobrevivencia post-volanton de al menos algunas aves. La tasa tan alta de recobro, éxito en dejar el nido y sobrevivencia post-volantón indican que en el Albatros de Laysan hay una alta inmunidad hacia la viruela aviar. [source] | ||||||||||