Egg size variability between clutchesof Choughs  (Pyrrhocorax pyrrhocorax)

TELLA, J.L., JOVER, LL. and RUIZ, X.

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Abstract:

The main sources of egg-size variability al interclutch level (clutch size and female) have been analyzed for 57 pairs of Choughs breeding at the Ebro Valley (Monegros) area in 1992. Egg-size variability is not affected by clutch size variation (4,5 and 6 eggs), whereas it is influenced by female characteristics. These results are discussed in relation to the findings in other birds, particularly Corvidae, and a final hypothesis, taking into account the existence of sexual dimorphism and courtship feeding behaviour in these birds, is emitted to explain them.