caa a22 4500 463174933 CHVBK 20180406164823.0 cr unu---uuuuu 170326e20070101xx s 000 0 eng 10.1007/s10336-006-0112-2 doi (NATIONALLICENCE)springer-10.1007/s10336-006-0112-2 Impaired hatching success and male-biased embryo mortality in Tree Sparrows [Elektronische Daten] [Magnus Svensson, Pekka Rintamäki, Tim Birkhead, Simon Griffith, Arne Lundberg] During the past 30years, many species of farmland birds have declined dramatically in numbers in Northern Europe, a trend coinciding with a tremendous intensification of agriculture, although the exact causes of these declines remain unclear. One of the worst affected species is the Tree Sparrow (Passer montanus). We studied two Swedish Tree Sparrow populations during the years 1996-2004 and found that in both populations, almost half of all laid eggs remained unhatched. This led us to investigate whether the eggs failed to hatch because of: (1) eggs not being fertilised or (2) embryo mortality. Our analyses showed that all of the eggs investigated contained sufficient number of sperm for fertilisation and that they also had other visible signs indicating that fertilisation had occurred. Hatching failure was instead shown to result from embryo mortality. Using molecular techniques, we were able to determine that embryo mortality is more likely to affect male embryos than females and that the fledgling sex ratio was consequently highly female biased. The cause of this sex-biased embryo mortality remains unknown, but various potential explanations are discussed. Dt. Ornithologen-Gesellschaft e.V., 2006 Eggs nationallicence Embryo mortality nationallicence Fertilisation nationallicence Passer montanus nationallicence Sex ratio nationallicence Svensson Magnus Population Biology and Conservation Biology, Department of Ecology and Evolution, Uppsala University, Norbyvägen 18D, 75236, Uppsala, Sweden aut Rintamäki Pekka Population Biology and Conservation Biology, Department of Ecology and Evolution, Uppsala University, Norbyvägen 18D, 75236, Uppsala, Sweden aut Birkhead Tim Department of Animal and Plant Sciences, University of Sheffield, S10 2TN, Sheffield, UK aut Griffith Simon School of Biological, Earth and Environmental Sciences, University of New South Wales, Kensington, 2052, Sydney, NSW, Australia aut Lundberg Arne Population Biology and Conservation Biology, Department of Ecology and Evolution, Uppsala University, Norbyvägen 18D, 75236, Uppsala, Sweden aut Journal of Ornithology Springer-Verlag 148/1(2007-01-01), 117-122 0021-8375 148:1<117 2007 148 10336 https://doi.org/10.1007/s10336-006-0112-2 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s10336-006-0112-2 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Svensson Magnus Population Biology and Conservation Biology, Department of Ecology and Evolution, Uppsala University, Norbyvägen 18D, 75236, Uppsala, Sweden aut NATIONALLICENCE 700 1- Rintamäki Pekka Population Biology and Conservation Biology, Department of Ecology and Evolution, Uppsala University, Norbyvägen 18D, 75236, Uppsala, Sweden aut NATIONALLICENCE 700 1- Birkhead Tim Department of Animal and Plant Sciences, University of Sheffield, S10 2TN, Sheffield, UK aut NATIONALLICENCE 700 1- Griffith Simon School of Biological, Earth and Environmental Sciences, University of New South Wales, Kensington, 2052, Sydney, NSW, Australia aut NATIONALLICENCE 700 1- Lundberg Arne Population Biology and Conservation Biology, Department of Ecology and Evolution, Uppsala University, Norbyvägen 18D, 75236, Uppsala, Sweden aut NATIONALLICENCE 773 0- Journal of Ornithology Springer-Verlag 148/1(2007-01-01), 117-122 0021-8375 148:1<117 2007 148 10336 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer