Sunday, January 6, 2013

Ringing the 2012 Cohort

In order to be able to follow individuals birds and their life history, they must be uniquely marked.  This is a key component for the population studies, and especially following the dispersal and survival of young birds.  

Marking involves both SAFRING identification rings and plastic CB rings, which with their bright contrast and large codes allow much easier recognition and reporting of individual eagles in the field.  The nestlings must be ringed within a specific time frame; to be fully or near-fully grown to fit the ring well, but not so mentally mature to think they could jump to escape this approaching monster.  Fortunately we were able to age these birds well and time the climbs appropriately, ringing eight between December and early January. Ringing juveniles and nestlings are particularly valuable because we know their age and origin, and could provide some very interesting longevity and dispersal data in the decades to come.

The behavior of the birds is very interesting.  I had expected more aggression from the adults, such is the need for a riot helmet and foam filled backpack.  Fortunately all birds appeared reluctant to attack.  Two nests that I have accessed have involved birds that were prepared to frighten me by a flyby within about five meters.

The nestlings generally show a threat display as they first see me broach the edge of the nest, facing head on with mouth agape and wings outstretched.  However as I climb further they may realize just how massively outsized I am, and their next response is to go completely catatonic. This is very fortunate in that I can place a bag next to the bird and simply lift it across, zip up, and lower it down.  The young eagle is kept in the dark and hooded while still in the bag.  They generally remain calm and docile while hooded, even during all the handling and measurements.

Our procedure has been well practiced now, and although the time it takes to get a rope in a good position for access can vary greatly, the process of removing the chick from nest and back takes all of about 20-30 minutes - depending mostly on the height of the climb back to the nest.

*awaiting more photos of nestlings and nests*

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