Snavelafwijking bij een ééndagskuiken van de Sperwer Accipiter nisus

Beak anomalies occur in 5% of all dead Sparrowhawk embryos obtained from failed eggs (n= 184). In some cases, the upper mandible is lengthened and not bend downwards at the tip. In 2001, for the first time a dead hatchling displaying this feature was found near Ede in the central Netherlands. Its siblings were 6-8 days older (as shown by tarsi measurements), making the anomalous chick unfit to compete for food. The absence of yolk in its abdomen indicates that it did not die immediately after hatching. As beak anomalies may be linked to nutritional shortages that also cause retarded growth, the position of the abnormal chick in the clutch cannot be deduced from its developmental age.