Action D4. Monitoring the colonies of Larus Audouinii and Phalacrocorax aristotelis desmarestii.

Partner: Direcció general de Biodiversitat

To monitor colonies inhabiting areas included in the project , and most specially those birds using places which are most easily accessible to uncontrolled visits by humans, dogs and other disturbing elements.

Methods and techniques:
These campaigns covered the most important colonies of Audouin Seagulls—in terms of number of birds—( which generally build nests in the areas accessible to humans, even if these birds sometimes change their nesting location from year to year). Also, a variable number of Common Shag Cormorant colonies were covered, and the exact number of Cormorant colonies monitored depended on the time and resources spent monitoring colonies of Audouin Seagulls.
In no case less than five. The control of the colonies was complemented by adequate sign posting. The goal was to prevent humans from bothering the birds as this is one of the endangering activities described in the Community Action Plans. For this action a Service Contract was drawn up to hire the services of Tragsa and the action was carried out with the collaboration of specialist experts from the Servicio de Protección de Especies ( Service for the Protection of Species), and engaging the help of bird-watching groups and conservationist NGOs able to mobilize volunteers which were given the adequate means (optical and security equipment, transport, etc.).
The action was carried out between the months of December 2003 and June 2004 and also between December 2004 and June 2005.
In December the communities of Common Shag Cormorant that were to be monitored were identified and it was decided where sign posts would be placed. In April the same was done for the communities of Audoin Seagulls. The work was carried out in the ensuing months.

Monitoring was done both by land and sea (using pneumatic “zodiak” type boats).
Digital photographs were taken of the colonies and further land and sea trips taken, with repeated visits to colonies that had already been studied and new visits to colonies that had not previously been studied.
Visits were repeated each year in order to better follow how things were going in each colony and to check data so that contrasting these would result in the most useful information.
In the following months, the breeding ones, the work of ringing the legs of chicks with identification rings continued. This task had been begun the first year.
This ringing is done with numbered metal and PVC rings and allows the identification of the individual at a distance using binoculars.
Existing colonies were checked and new nests identified. At the same time a photographic inventory was made in order to be able to photographically identify the individuals.
The surveillance and tracking of the Majorcan colonies was carried out in the following areas:

• Coast of Cap Enderrocat and Cap Regana
• Sa Dragonera Island
• Coast of Tramuntana, between the Port of Sóller and Cap de Formentor
• Coast of the Artà mountain
• South-west coast of Majorca
• Formentor Island and Victoria Peninsula

L. audouinii
During 2005 the census of Audouin Seagull was counted again in the Balearic Islands and in the other colonies of Spain where most of the world’s reproducing population of this species, endemic in the Mediterranean, lives. The collected data is as follows:

Majorca: 76 couples on the island of Moltona (Ses Salines) at 3 locations, 15 couples on the island of Pelada (Ses Salines), 150 couples at Cap Enderrocat (Llucmajor), 15 couples on the island of Sa Dragonera (Andratx) who deserted, and 28 couples at Cap des Freus (Capdepera).

Minorca: 113 couples at two locations of 75 and 38 on the island of Aire (San Luís), an estimated 80 couples on the islands of Porros (Es Mercadal), and an estimated 18 couples at Punta Perpinyá (Ciutadella). Source: Minorcan Ornithology Society-Raül Escandell.

Ibiza: 46 couples at Escull d’en Terra (Ibiza), 108 couples on the island of Santa Eulaia (Santa Eulalia), 264 couples on the island of Espartar, 94 couples on the island of Cala Salada (San Antonio) and an estimated 35 reproducing couples on the island of Calders (Sant Joan).

Formentera , 231 couples on the island of Espardell (San Francisco Javier).

Cabrera: 197 couples at one location on Cala Estreta, Conejera (Source: National Park of Cabrera).

Negative census at:
Mallorca: islets off Colonia Sant Jordi (Ses Salines, coast of Llucmajor, islets in the Bay of Palma (Palma and Calviá), coast of Rafaubeitg, island of el Toro and Malgrat islands (Calviá). It was not possible to carry out a census on the island of Formentor.

Minorca: Cap de Cavalleria (Es Mercadal)

Ibiza: island of Tagomago (Santa Eulalia), islets of Freus (Ibiza and San Franciso Javier), the other western islets (San Antonio).

Formentera: la Mola and Cap Berbería.

Cabrera: the other islets of the archipelago.

It can be said that the designated areas were well covered. The total results are:

Majorca -----> 284 couples
Minorca-----> 211 couples
Ibiza ------> 546 couples
Formentera --> 231 couples
Cabrera ------> 197 couples
Total ----------> 1,469 couples

These facts indicate there has been a slight recovery with respect to the census of 1,195
couples counted in 2004, and the number is almost the same as the census of 2003 in which 1,389 couples were counted. The maximum population of the Balearics was that of 1,956 reproducing couples counted in 2001. This census was carried out by many people, most connected to the local Ministry of the Environment ( Consellería de Medi Ambient) and pertaining to several departments such as the General Directorates of Biodiversity, Hunting, Protection of Species, and Environmental Education, plus persons pertaining to Ibanat, and volunteers.

During the three-year period spanning 2003-2005, the work of monitoring and locating colonies of Audouin Seagulls continued, as well as the work of elaborating a census of nesting couples, ringing chicks, reading the rings and keeping an eye on the breeding spots. The Balearic population of Audouiin Seagull reached its maximum peak in 2001, when 1,956 reproducing couples were counted. From that year on the population decreased slowly until 2005 when there was a slight recovery in number. In 2003, 1,389 couples had chicks, in 2004 the number of reproducing couples descended to 1,195 and in 2005 the number increased slightly to 1,469 reproducing couples. The number of spots occupied for breeding purposes has not varied much during this period, although variations in the location of colonies has continued as there were 13 in 2003, 16 in 2004, and 15 in 2005. With respect to the Spanish population, which is the most important in the world, the Balearic population constitutes 5.77 % (in 1997) and 10.93 % (in 2001) of the total.

P. aristotelis
In order to monitor this species and track the colonies of Majorca, visits by land and sea (pneumatic “zodiak” type boats) were carried out.
In total there were 33 visits of which 9 were by sea and 24 by land. The following were located:
339 nests
27 probable nests
92 sure nests
49 empty nests
167 nests with an adult sitting on the eggs
19 nests with chicks

During the nest counting the following were observed: 310 individuals of which 234 were adults, 55 were of around one year of age, and 21 were immature.

Digital photographs were taken and GPS data compiled of the colonies and of dispersed nests.
Chicks were ringed as follows: 26 in 2004 and 29 in 2005 in three colonies of Majorca and Cabrera. 34 in 2005 in 4 colonies of Ibiza and Formentera. 27 in 2003, 18 in 2004 and 15 in 2005 in 7 colonies of Minorca.

It has been established that human presence occurring during the observation periods did not greatly disturb the birds, except in two cases: one in Vallgornera (Llucmajor) where a fisherman and his equipment were found very near three nests, and the other in Bahía Azul (Llucmajor) where there was an adult bird sitting on the eggs and just four metres below there were three people fishing with rods from the rocks.

It seems the population has suffered a decrease in comparison with the last census of 2004. The reasons could be very varied, such as: long-line fishing, nets, boat traffic, regeneration of beaches, an increase in the population of common seagulls, etc. Nevertheless, naturally occurring fluctuations cannot be ruled out.
It can be said that the aims of this action have been fulfilled as data is now available on the population of both these species and this type of work will continue to be regularly carried out in order to monitor how both populations evolve.

Detail of the monitoring work

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Photo 2