PATERNITY GUARDING IN THE YELLOWHAMMER EMBERIZA-CITRINELLA - A DETENTION EXPERIMENT

The importance of male presence on their territories for maintaining p aternity in their mates' offspring was investigated in the Yellowhamme r. Males were experimentally detained for one hour before and during t heir mate's fertile period. When males were detained, their territorie s received an increased number of intrusions and intruding males. Also the duration of intrusions increased compared with when they were pre sent on their territories. No difference was found in intrusion patter ns between the prefertile and the fertile period. No intrusions were o bserved during the post-fertile period. The rate of intrusion was not related to number of neighbouring males although young males suffered from a higher intrusion rate when the number of young neighbouring mal es increased. Old males with much yellow were subject to more intrusio ns than other males, predominantly by other older males, indicating a cost of wearing colourful plumage. In spite of the low intensity, or a bsence, of mate guarding found in a previous study of the Yellowhammer , results indicate that male presence on their territories may reduce the potential for extra-pair fertilizations.