A day's work at the Bird Observatory

The Gibraltar Ornithological and Natural History Society's Bird Observatory is sited on the Upper Rock Nature Reserve, at Jews' Gate. Its primary function is the monitoring and research into passerines and non-passerines, with particular emphasis on migration.


The research is aided by data obtained through the process of the capturing and ringing of birds by well-qualified ('A') ringers, mainly based in the UK, who volunteer to man the operation for varying lengths of time from a couple of weeks to several months at a time. Trainee ringers looking to gain experience are welcome, provided there is a trainer available or an 'A' ringer to supervise them.There is no resident ringer.It's a popular venue, and bookings must be made to ensure the availability of the accommodation provided. (Bookings are accepted on a 'first come, first served' basis and are managed by Jill Yeoman.)

The Bird Observatory and accommodation facilities are based here at the field centre on the Upper Rock

The building is modest, but the accommodation has everything needed to be fairly comfortable and there's no question that the views it commands are spectacular.

The view from the Observatory doorway, looking across the Bay

Autumn is a particularly demanding time for the ringers in residence, when the migration of a myriad of bird species is at its height and the mist nets may capture dozens of birds that require processing for data. 

A Chiffchaff caught in a mist net

For the ringing operation mist nets are used in an area of Mediterranean matorral dominated by Olive Olea europaea and Lentisc Pistacia lentiscus. The total maximum length of the line of nets is 800 m, with an average of 400m used at any one time. Ringing is carried out on days of suitable weather from February to June and August to November.

Chiffchaff being carefully extricated from netting

A truly beautiful, tiny Serin

The nets are checked in rotation about every half-an-hour or so, the regularity dependent to an extent on the number of ringers present and the numbers of birds being caught. 

A Robin protesting at being held upside down

The welfare of each individual bird is paramount and their handling must be quick, decisive and sensitive.Experienced ringers can extricate a bird from a net in a few seconds; they first assess in which direction the bird was flying when it was caught, then release it by combining the correct grip on the bird with some deft and practised unravelling. 

The nets are very fine but strong enough to support a healthy Song Thrush

A beautiful bright-eyed bird, this song thrush was quite feisty and voiced its protest at the indignity of being caught 

Ian, the current resident ringer carrying in birds

Once a bird has been released it is carefully placed in a cloth bag, where the absence of visual stimuli helps to keep it calm. When all of those caught are collected they are quickly carried back to the Observatory for processing.


The bags are hung from hooks numbered to correspond with the number of nets in use. There are potentially 20 nets that may be 'open'; today there were 18 in use.


The birds are processed methodically and great attention is paid to accurate identification, ageing, measuring, weighing and assessing the general health of each individual, including how much muscle it has and the fat store it has managed to accumulate.


As Ian said, "There is absolutely no point to ringing birds and recording data if it is not 100% accurate."  

Bags of birds

Strings of rings

Bird ringing is carried out under the auspices of the BTO, British Trust for Ornithology, and Gibraltar uses British rings.


The rings are sized with AA being the smallest and C the largest. 


AA ring: Serin
  A ring: Robin, Black Redstart, Blackcap
  B ring: Greenfinch, Woodchat Shrike
CC ring:Orphean Warbler, Song Thrush
  C ring: Cuckoo, Hoopoe

Measuring the length of a Robin's wing

One of today's pages from the data record book

As soon as all required data has been obtained, the birds are set free. Most will set off on their travels and will not been seen again, but a few will stay around for a few days and may find themselves here again, sometimes more than once and will be recorded as a 're-catch'.

A female Blackcap posing for a photograph before flying away

She was reluctant to leave and sat on Jill's open hand for a few seconds

A male Blackcap was much keener to leave

The browner plumage of this well-marked Chiffchaff identified it as northern European 

On a particularly 'heavy' day there may be between 200-250 birds to process. This morning 113 were recorded, mainly Black Redstart, Blackcap, Robin and Chiffchaff with many juvenile birds making their first migration. There were also a few Song Thrush and a beautiful male Serin.


Visitors are welcomed at the Observatory, but as the welfare of the birds is the primary consideration of the working ringer, this must be respected. Most ringers prefer to work as quietly as possible as undue noise will disturb the birds. They may also be very busy and prefer not to be distracted from their work, so be prepared to be asked to be quiet, or even asked to leave the building.