AVIS-IBIS

Birds of Indian Subcontinent

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

Publication Type:Journal Article
Year of Publication:2005
Authors:Ležalová, R, Tkadlec, E, Oborník, M, Šimek, J, Honza, M
Journal:Journal of Avian Biology
Volume:36
Issue:6
Date Published:2005
ISBN Number:1600-048X
Keywords:Chroicocephalus, Chroicocephalus ridibundus, Laridae, Larus, Larus ridibundus
Abstract:In birds with hatching asynchrony and sexual size dimorphism, 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. Time of breeding had no effect on offspring sex or hatchling sex ratios.
URL:http://dx.doi.org/10.1111/j.0908-8857.2005.03466.x
Short Title:Journal of Avian Biology
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith