INTRASPECIFIC VARIATION IN LENGTH OF INCUBATION PERIOD IN AVOCETS RECURVIROSTRA-AVOSETTA

This paper investigates factors influencing the intraspecific variabil ity of incubation periods in Avocets Recurvirostra avosetta. The lengt h of the incubation period of 278 clutches ranged from 19 to 34 days w ith an average of 23.1 days. Incubation period was influenced by clutc h size. There was a seasonal decrease in incubation period resulting i n a difference of 1.7 days between the earliest and the latest clutche s. The seasonal trend could not be explained by ambient temperature. N o relationships could be found between incubation period and colony si ze, nest density, or habitat. There were significant positive correlat ions between incubation period and bill length and foot length of the neonates. The possibility that incubation period is influenced by a tr ade-off between egg and chick mortality rates and embryonic and chick growth rates is discussed.