Saturday, 2 June 2012

Black Vultures & Spanish Imperial Eagles

Another trip to the Castro Verde area this week produced most of the expected species.  Little Bustards were an exception - at this time of year, when they have finished displaying and are no longer vocal, they need a bit of effort to find and on this occasion they weren’t a priority.

That the ‘expected species’ now include Black Vulture and Spanish Imperial Eagle says much about the change that there has been in the status of these two birds in recent times.  Not so many years ago, seeing either of them in Portugal would have made for a ‘red letter day’.  

Both declined as a result of a combination of factors.  The most serious of these were the indiscriminate use of poisoning as a means of controlling ‘vermin’, collisions with power lines, decreased food availability caused by European Union legislation on carcass disposal, the drastic decline in the population of European rabbits and habitat changes in their breeding areas.

In a study that examined the deaths of 267 Spanish Imperial Eagles (in Spain) between 1989 and 2004, 91.7% of the causes of mortality (where the cause of death could be determined) were of human origin. Electrocution and poisoning were by far the most common causes of death. 115 Spanish Imperial Eagles were electrocuted and 74 were poisoned.

Although some Black Vultures are electrocuted that doesn’t seem to be such a regular problem for them as it is for Spanish Imperial Eagles.  For vultures, illegal poisoning is a much more serious problem.  Since 1990, about 500 victims of poisoning are reported to have been found.

In recent years, great efforts have been made, particularly in Spain, to tackle these problems and thankfully both species have responded well with their populations showing remarkable recoveries and birds now spreading west into the Alentejo.

Because it’s what we’ve been accustomed to over many years, we still use the name 'Black Vulture' or sometimes ‘Eurasian Black Vulture’, which, of course, refers to the birds’ plumage colour.  An alternative, more recently adopted name is 'Monk Vulture', which is a direct translation of its German name Mönchsgeier, referring to the bald head and ruff of neck feathers like a monk's cowl.  The IOC World Bird List uses the name 'Cinereous Vulture', an attempt to rename the species to avoid confusion with the American Black Vulture.

‘Spanish Imperial Eagle’ is a bit of a mouthful and we’re inclined to refer to them as ‘Spimps’!  Of course, it’s not so long ago that they were just the western population of ‘Imperial Eagle’, regarded as conspecific with what we now know as 'Eastern Imperial Eagle'.  Maybe, if the present population trend continues we’ll soon hear them referred to as ‘Iberian Imperial Eagles’.

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