Just in Time…

In my post Old Acquaintance early November I wrote about the return of 23-year old Black-headed Gull (Chroicocephalus ridibundus) with Dutch ring Arnhem 3431752.

This observation made it clear that the ring (made out of aluminum) was in such a bad state that it would probably not be long before the ring would be lost.

Black-headed Gull, 24cy, worn ring, M[Arnhem 3431.752]
State of the ring on 13 November 2011, Leiden, The Netherlands.
 

Because of the old age of this gull, it would have been a shame for it to lose the ring and for us not being able to follow it over the coming years. Plans were therefore made to try to capture it and fit it with new rings.

To increase the chance of capturing it again, a pattern of its whereabouts was trying to be established. Fortunately, gulls have a high site-fidelity (preference to stay at or near a particular location) and it was seen on-and-off at various locations within a small area. It also turned out that it was easy to attract it with bread, but that it would only feel comfortable on the ground when there were not too many other gulls around. As soon as the group was too large, it would take off again.

On Saturday December 24 the first attempts were made but these were unsuccessful because of the group of gulls being too large and due to too much disturbance by passers-by.

A second attempt on Sunday the 25th at a location nearby turned out to be successful. It was caught and re-fitted with a metal ring and a color ring. Because the aluminum ring was set tightly on the right foot, the metal ring (code Arnhem 3.729.911) was placed on the right tibia (upper leg) instead. A color ring (White E0TU) was added to make the individual better recognizable (re-sightings of color-ringed birds are far higher than those wearing only metal rings).

We will have to see how this bird will react to its re-capture and if it will stay in the area; it is known for older birds which are caught to lose their habits and for instance move to a different area. Wherever it might end up, we hope to receive many re- sightings of this individual for many more years.

Black-headed Gull, 24cy, M[Arnhem 3431.752]
Shortly after being caught: the old ring is set tight just above the foot.
 
Black-headed Gull, 24cy, M[Arnhem 3431.752]
The old ring showing heavy wear; the indentations at the top are caused by the fact that the ring was positioned upside down.
 
Black-headed Gull, 24cy, W[E0TU]
The new rings being fitted.
 
Black-headed Gull, 24cy, W[E0TU]
Being measured; based on the length of the distance between the head and tip of the bill, this individual is determined to be male.
 
Black-headed Gull, 24cy, W[E0TU]
The head pattern of this individual during winter consists of only a small ear spot and very faint bands across the head.
 
Black-headed Gull, 24cy, W[E0TU]
The pattern of the primary feathers; P9 shows a black mark.
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