Egg burial in penduline tits, Remiz pendulinusr.its role in mate desertion and femalepolyandry

One important component in the mating strategy of an already-mated individual is the decision to remain with the partner and care for the offspring or to desert. Almost all research on nest desertion has focused on the costs and benefits of continued parental care versus desertion of both parents. However, if it pays both parents to desert, the timing of desertion is most important In birds, where all eggs are fertilized well before the last egg is laid, males should be the first to desert. Even if females try to hide their fertile period, it is likely that the appearance of eggs acts as a cue that males can use to calculate the timing of their desertion. Here we examine egg burial behavior in penduline tits and its possible effects on parental behavior and desertion. Penduline tits perform uniparental care from the earliest point of breeding, and both sexes try to become polygamous. We found that 36% of investigated males were polygynous and deserted as soon as the first egg appeared in their nest, and 12-5% of females became poryandrous. About 27% of the nests were deserted by both sexes, which means high costs for females in terms of wasted energy in eggs and for males in terms of wasted energy and time in building elaborate nests. Females cover the eggs, and several facts indicate that egg covering is a deceptive ‘behavior of females: (1) females cover the eggs in the morning before leaving the nest for the first time, (2) females are more aggressive toward their mates during the laying period than before laying, (3) females try to prevent males from entering the nest when eggs have been experimentally uncovered, and (4) females uncover the eggs as soon as males are experimentally removed. Finally, we found that a female can only desert the nest before the male deserts when she covers the eggs. We conclude that the higher the proportion of eggs a female can hide, the greater her chance of becoming potyandrous

F. Valera, H. Hoi, and B. Schleicher, Behavioral Ecology VoL 8 No. 1: 20-27