Egg Morphology and Clutch Size in Shrikes (Laniidae) From Historical Oological Collections: Interspecific Patterns...

Avian eggs reflect life-history trade-offs, and museum collections provide a valuable historical resource for examining how egg morphology and clutch size vary across species, space and time. However, shrikes (Laniidae), despite their ecological distinctiveness and broad distribution, still lack a comparative analysis of egg morphology and clutch size across species. Using historical oological collections spanning 1888-1973, we quantified inter- and intraspecific variation in egg morphology and clutch size in four shrike species: red-backed shrike (Lanius collurio), woodchat shrike (L. senator), lesser grey shrike (L. minor) and great grey shrike (L. excubitor). Across the historical collection period, clutch size increased over time only in the lesser grey shrike, whereas no robust temporal trend was detected in the other species. Where temporal trends in egg morphology occurred, size-related traits generally declined, whereas shape descriptors, including sphericity and shape index, remained comparatively stable. Among species, the great grey shrike laid the largest eggs and had the smallest clutches, while the lesser grey and woodchat shrikes had the largest clutches with smaller eggs, consistent with a broad size-number trade-off in reproductive allocation. Within species, spatial variation in egg-size traits was evident, particularly in the red-backed shrike and woodchat shrike, whereas evidence for a size-number relationship was weak. Overall, temporal change in shrike reproductive traits was limited and species-specific, while museum collections proved valuable for reconstructing long-term patterns of reproductive variation.