Should males come first? The relationship between offspring hatching order and sex in the black-headed gull Larus ridibundus

0024396 - ÚBO 2006 RIV GB eng J - Journal Article
Ležalová, R. - Tkadlec, Emil - Oborník, M. - Šimek, J. - Honza, Marcel
Should males come first? The relationship between offspring hatching order and sex in the black-headed gull Larus ridibundus.
[Měli by se samci líhnout první? Vztah mezi pořadím líhnutí a pohlavím u racka chechtavého (Larus ridibundus).]
Journal of Avian Biology. Roč. 36, č. 6 (2005), s. 478-483. ISSN 0908-8857. E-ISSN 1600-048X
R&D Projects: GA ČR(CZ) GD206/05/H012
Institutional research plan: CEZ:AV0Z60930519
Keywords : black-headed gull * egg sequence
Subject RIV: EG - Zoology
Impact factor: 1.752, year: 2005

In birds with hatching asynchrony, chicks hatched earlier and later in the laying sequence usually suffer different mortalities due to uneven abilities to compete for food, especially in poor years. If sexes differ in vulnerability to environmental conditions, e.g., by having different food requirements due to differential growth rates, mothers can increase fitness by allocating sex according to the laying order, producing less vulnerable sex later rather than early in the clutch. By analysing variation in primary sex ratio using a PCR-based DNA technique, we tested this prediction in black-headed gull Larus ridibundus chicks where males may be the less viable sex under adverse conditions. The overall primary sex ratio of the population did not depart from parity. However, first hatched chicks were more likely to be males whereas last hatched chicks were more likely to be females. Both egg volume and hatchling body mass decreased with laying order irrespective of sex.

U ptáků s asynchronním líhnutím mláďata vykazují rozdílnou mortalitu ovlivněnou pořadím snesené vajec. Za určitých podmínek jsou samice schopny alokovat pohlaví ve snášení. Analýzou poměru pohlaví pomocí PCR DNA technikou jsme analyzovali poměr pohlaví u racka chechtavého. Zjistili jsme, že více nákladné pohlaví samčí se objevovalo ve snůškách dříve než pohlaví samičí.
Permanent Link: http://hdl.handle.net/11104/0114945