Tawny owl reproduction and offspring sex ratios under variable food conditions |
| |
Authors: | Jaana Kekkonen Heikki Kolunen Hannu Pieti?inen Patrik Karell and Jon E Brommer |
| |
Institution: | (1) Bird Ecology Unit, Department of Biological and Environmental Sciences, University of Helsinki, (Viikinkaari 1), P.O. Box 65, Helsinki, 00014, Finland;(2) Nikkarinkatu 52, Lahti, 15500, Finland |
| |
Abstract: | Tawny owl reproduction and offspring sex ratios have been considered to depend on the abundance of small voles. We studied
reproductive performance (laying date, clutch and brood size) during 1995–2003 and offspring sex ratios from 1999 to 2003
in relation to the abundance of small voles and food delivered to the nest in a tawny owl population in southern Finland.
Abundance of small voles (field and bank voles) was based on trappings in the field, and estimates of food delivery was based
on diet analysis of food remains in the nest boxes. In this population, reproductive output was not related to the abundance
of small voles. Analysis of food delivered to the nest showed that the prey weight per offspring varied more than twofold
between years and revealed that this difference was mainly related to the proportion of water voles in the diet. Only the
number of water voles correlated with laying dates. Offspring sex ratios were weakly male biased (55%) but did not differ
from parity. Sex ratios were not related to the abundance of small voles, and we found no evidence that parents delivered
more food to nests with proportionally more offspring of the larger (female) sex. Our results underline the notion that populations
may differ in their sex allocation pattern, and suggest such differences may be due to diet. |
| |
Keywords: | Diet Food supply Life history Sex allocation Sexual dimorphism Water vole Arvicola terrestris |
本文献已被 SpringerLink 等数据库收录! |
|