Apologies for this week’s late posting.
I wakened in the course of the night time with a Blackbird (Turdus merula) persistently singing from a tree exterior. It was 5 within the morning and dawn was nonetheless three hours away. The noticeably growing daylength after twenty first December quickly will get native birds into the mindset of breeding. In actual fact, I typically see Blackbird fledglings round now, suggesting they begin breeding even earlier than the times begin to lengthen. Different native residents additionally begin breeding presently however I’m going to focus at this time on two of the biggest species. These are the Bearded Vulture (Gypaetus barbatus) and the Griffon Vulture (Gyps fulvus). Bearded Vultures vary in physique mass from 4.5 to 7.1 kilos whereas Griffons vary between 6.2 and 11.3 kilos, females being heavier than males.
The big physique mass locations critical constraints on breeding. Griffons lay a single egg. Bearded Vultures lay two however just one chick survives, inter-sibling aggression caring for that. The event of such a big fowl takes time. In each instances it takes between 5 and 6 months from laying of the egg and the chick fledging. On condition that the summer time months are traumatic in southern Europe, with little rain, and with shortening days, these birds have to start out breeding early. That implies that many Bearded and Griffon Vultures are actually sitting on eggs.
Breeding excessive up within the mountains, particularly Bearded Vultures, poses further difficulties. Incubating the eggs requires fixed consideration however the adults must feed. One trick is to gather wool, shed by sheep within the mountains, and use this to line the nest. This offers insulation that’s a lot wanted at altitude. For a number of months, and till the chick within reason massive, Bearded Vultures reside with the specter of chilly nights and blizzards.
Bearded Vultures are sedentary. They should be on territories as quickly as they can begin the breeding cycle. The identical is the case with grownup Griffons. At Gibraltar we observe hundreds of Griffon Vultures heading south for tropical Africa in October and November they usually don’t return till the spring, particularly from late April to June. They’re all immature birds. They only couldn’t return so late and try to breed. There simply wouldn’t be ample time. However the adults can’t afford the posh of transferring south to hotter climes within the winter. They’ve to remain put.
