Bearded vultures lay 1-3 eggs but tend to favor the oldest chick, even allowing it to cannibalize the other chicks.
Female bearded vultures lay one to three eggs per breeding cycle, with usually only one egg surviving. In the Pyrenean population, there is extremely low breeding productivity with only an average of 0.4 fledglings per pair per year.
Mean hatching asynchrony between eggs in bearded vultures is estimated to be six days, longer than in any other raptor.
The first chick is usually larger, more active, has a more erect posture, and can call more insistently than the second chick. Parental favoritism towards the first chick is common among bearded vultures, and parents may only feed the first born.
The second chick often dies very quickly, and is frequently fed to the first chick for nourishment. The poor ability of the second chick to fend for itself may be an adaptation to a quick death if the first chick survives. At the same time, the second egg may act as insurance in case the first does not survive.
Sources: (Margalida & Bertran, 2005; Margalida, Garcia, Bertran, & Heredia, 2003; Tenenzapf, 2011)
Image: Cloudtail the Snow Leopard
