Ardea
Official journal of the Netherlands Ornithologists' Union

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Soler M., Soler J.J. (1992) Latitudinal trends in clutch size in single brooded hole nesting bird species a new hypothesis. ARDEA 80 (2): 293-300
In the Jackdaw Corvus monedula clutch size decreases significantly with increasing latitude. Our data provide an exception to the commonly accepted observation that avian clutch size tends to increase with latitude. We suggest that (1) the advantages of small clutches are not important in The Jackdaw, since larger clutches are the most productive ones, and (2) an opposite latitudinal trend between clutch size and egg size suggests a trade-off between laying few large eggs or many small eggs. We hypothesize that in the Jackdaw, and in general, in other single brooded hole nesters, large clutches are advantageous, and clutch size decreases with latitude because it is limited by proximate constraints put on the females of producing large eggs given that in the north large eggs provide a selective advantage.


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