Action: Provide supplementary food to allow the rescue of a second chick
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A small controlled study in Spain found that second chicks from lammergeier Gypaetus barbatus nests survived longer if nests were provided with food, allowing one chick to be rescued.
Many vultures and birds of prey lay more eggs each year than they can raise, with the final chick hatching several days after the first. This chick will always be weaker and is almost always killed by its siblings or starves to death as it cannot compete for food. It is thought that this chick acts as ‘insurance’ in case the older chicks die.
In very rare species, it may be beneficial to ‘rescue’ the younger chick, but doing so can be difficult. It is possible that providing extra food will allow the yonger chick to survive for long enough for a rescue attempt to be mounted.
Supporting evidence from individual studies
A small controlled study in the Spanish Pyrenees in spring 2004-5 and 2008 (Margalida et al. 2009) found that second-hatched lammergeier (bearded vulture) Gypaetus barbatus chicks from two nests provided with supplementary food survived for nine days, as opposed to seven, five and four days for a partially-supplemented nest and two control (unfed) nests, respectively. In a third supplemented nest (in 2008), the second-hatched chick survived for five days and was removed to be hand-reared and incorporated into a captive-breeding programme. Supplementary food consisted of 2-3 kg of dead rabbits within 100 m of the nests every two days from the hatching of the first chick until the death (or removal) of the second chick. The partially-supplemented nest was provided with food on just one day.